THE LIBRARY
OF
THE UNIVERSITY
OF CALIFORNIA
PRESENTED BY
PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID
ANATOMICAL MEMOIES
OF THE LATE
JOHN GOODSIR
THE
ANATOMICAL MEMOIES
OF
JOHN GOODSIE
F.K.S.
LATE PROFESSOR OF ANATOMY IN THE UNIVERSITY OF EDINBURGH
EDITED BY
WILLIAM TUENEE, M.B.
PROFESSOR OF ANATOMY IN THE UNIVERSITY OF EDINBURGH
WITH A BIOGRAPHICAL MEMOIR BY
HENEY LONSDALE, M.D.
FORMERLY LECTURER ON ANATOMY
VOL. II.
EDINBURGH
ADAM AND CHARLES BLACK
1868
Printed by R. CLARK, Edinburgh.
l\ \J( I
CONTENTS OF VOL. II.
DIVISION I.
PAGE
I. ON THE ORIGIN AND DEVELOPMENT OF THE PULPS
AND SACS OF THE HUMAN TEETH . . 1
(Edinburgh Medical and Surgical Journal, Jan. 1839.)
II. ON THE FOLLICULAR STAGE OF DENTITION IN THE
RUMINANTS, WITH SOME EEMARKS ON THAT PRO-
CESS IN THE OTHER ORDERS OF MAMMALIA . 53
(Transactions of British Association for Advancement of
Science, August 1839.)
III. ON THE MODE IN WHICH MUSKET - BULLETS AND
OTHER FOREIGN BODIES BECOME INCLOSED IN
THE IVORY OF THE TUSKS OF THE ELEPHANT . 56
(Transactions of Royal Society of Edinburgh, January 18,
1841.)
IV. ON THE SUPRA -RENAL, THYMUS, AND THYROID
BODIES ...... 66
(Philosophical Transactions, January 22, 1846.)
V. ON THE MORPHOLOGICAL RELATIONS OF THE NER-
VOUS SYSTEM IN THE ANNULOSE AND VERTEBRATE
TYPES OF ORGANISATION . . . .78
(Edinburgh Philosophical Journal, January 1857.)
VI. ON THE MORPHOLOGICAL CONSTITUTION OF THE
SKELETON OF THE VERTEBRATE HEAD . . 88
(Edinburgh Philosophical Journal, January 1857.)
VII. ON THE MORPHOLOGICAL CONSTITUTION OF LIMBS . 198
(Edinburgh Philosophical Journal, January 1857.)
M370133
VI CONTENTS.
DIVISION II.
PAGE
VIII. ON THE EMPLOYMENT OP MATHEMATICAL MODES
OP INVESTIGATION IN THE DETERMINATION OF
ORGANIC FORMS ..... 205
(Daily Mail, July and August 1849.)
IX. ON THE HORIZONTAL CURVATURE OF THE INTERNAL
FEMORAL CONDYLE; ON THE MOVEMENTS AND
RELATIONS OF THE PATELLA, SEMILUNAR CARTI-
LAGES, AND SYNOVIAL PADS OF THE HUMAN
KNEE-JOINT . . . . . 220
(Edinburgh Medical Journal, July 1855.)
X. ON THE MECHANISM OP THE KNEE-JOINT . . 231
(Abstract in Proceedings of Royal Society, Edinburgh,
January 18, 1858.)
XI. ON THE CURVATURES AND MOVEMENTS OF THE
ACTING FACETS OP ARTICULAR SURFACES . 246
XII. LECTURE ON THE RETINA . . . .265
(Edinburgh Medical Journal, October 1855.)
XIII. ON THE MODE IN WHICH LIGHT ACTS ON THE ULTI-
MATE NERVOUS STRUCTURES OF THE EYE, AND
ON THE RELATIONS BETWEEN SIMPLE AND COM-
POUND EYES ..... 273
(Proceedings of Royal Society, Edinburgh, April 6, 1857.)
XIV. LECTURE ON THE LAMINA SPIRALIS OF THE COCHLEA 282
(Edinburgh Medical Journal, December 1855,)
XV. ON THE ELECTRICAL APPARATUS IN TORPEDO, GYM-
NOTUS, MALAPTERURUS, AND RAIA . . 289
(Edinburgh Medical Journal, August and September 1855.)
XVI. A BRIEF REVIEW OF THE PRESENT STATE OF OR-
GANIC ELECTRICITY ..... 306
(Edinburgh Philosophical Journal, October 1855.)
CONTENTS. VU
PAGE
XVII. ON THE CONFERVA WHICH VEGETATES ON THE SKIN
OP THE GOLD-FlSH ..... 345
(Annals and Magazine of Natural History, IX., 1842.)
XVIII. HISTORY OF A CASE IN WHICH A FLUID PERIODI-
CALLY EJECTED FROM THE STOMACH CONTAINED
VEGETABLE ORGANISMS OF AN UNDESCRIBED FORM
(SARCINA VENTRICULI) . ' . . . 351
(Edinburgh Medical and Surgical Journal, LVIL, 1842.)
XIX. ON A DISEASED CONDITION OF THE INTESTINAL
GLANDS ...... 372
(Edinburgh Monthly Journal of Medical Science, April
1842.)
XX. STRUCTURE AND PATHOLOGY OF KIDNEY AND LIVER 379
(London and Edinburgh Monthly Medical Journal, May
1842.)
Anatomical and Pathological Observations. Edin. 1845.
XXI. CENTRES OF NUTRITION .... 389
XXII. THE STRUCTURE AND FUNCTIONS OF THE INTES-
TINAL VILLI ..... 393
XXIII. ABSORPTION, ULCERATION, AND THE STRUCTURES
ENGAGED IN THESE PROCESSES . . . 403
XXIV. THE PROCESS OF ULCERATION IN ARTICULAR CAR-
TILAGES ...... 408
XXV. SECRETING STRUCTURES . . . .412
XXVI. THE TESTIS AND ITS SECRETION IN THE DECAPO-
DOUS CRUSTACEANS . . . .429
XXVII. THE STRUCTURE OF THE SEROUS MEMBRANES 430
Vlil CONTENTS.
PAGE
XXVIII. STRUCTURE OF THE LYMPHATIC GLANDS . . 439
XXIX. THE STRUCTURE OF THE HUMAN PLACENTA . 445
XXX. THE STRUCTURE AND ECONOMY OF BONE . 461
XXXI. THE MODE OF REPRODUCTION AFTER DEATH OF
THE SHAFT OF A LONG BONE . . . . 465
XXXII. THE MODE OF REPRODUCTION OF LOST PARTS IN
THE CRUSTACEA . . . . .471
XXXIII. OF THE ANATOMY AND DEVELOPMENT OF THE
CYSTIC ENTOZOA . ... 476
XXXIV. DESCRIPTION OF AN ERECTILE TUMOUR . 504
(Monthly Medical Journal, 1845.)
XXXV. DESCRIPTION OF A CONGENITAL TUMOUR OF THE
TESTIS ...... 506
(Northern Journal -of Medicine, 1845.)
XXXVI. THE CURVATURES OF THE ARTICULAR SURFACES
AND THE GENERAL MECHANISM OF THE HIP-
JOINT 508
EXPLANATION OF THE PLATES.
DEVELOPMENT OF THE TEETH. PLATE I. page 1.
a. Fig. 1. A tooth-germ a bulging on a mucous membrane.
b. Diagrams illustrating the three stages of dentition.
Fig. 1. Follicular. 2. Saccular. 3. Eruptive stage.
c. Diagrams illustrative of the formation of a temporary and its
corresponding permanent tooth from a mucous membrane.
Fig. 1. Mucous membrane. Fig. 2. Mucous membrane, with a gra-
nular mass deposited in it. Fig. 3. A furrow or groove on
the granular mass. (Primitive dental groove.)
Fig. 4. A papilla (a tooth germ) on the floor of the groove.
Fig. 5. The papilla enclosed in a follicle in the bottom of the groove
(the latter in the condition of a secondary dental groove).
Fig. 6. The papilla acquiring the configuration of a pulp, and its sac
acquiring opercula. The depression for the cavity of re-
serve behind the inner operculum.
Fig. 7. The papilla become a pulp, and the follicle a sac, in conse-
quence of the adhesion of the opercular lips. The second-
ary dental groove in the act of closing.
Fig. 8. The secondary groove adherent, except behind the inner
operculum, where it has left a shut cavity of reserve for the
formation of the pulp and sac of the permanent tooth.
Fig. 9. The last change rendered more complete by the deposition of
the granular body (the enamel organ of Hunter, Purkinje, and
Raschkow). Deposition of tooth substance commencing.
Fig. 10. The cavity of reserve receding from the surface of the gum,
and dilating it at its distal extremity, in which a pulp is
forming. Kudimentary opercula developing near its proximal
extremity and dividing it into a follicular and an extra-folli-
cular compartment. Temporary tooth pulp nearly covered
with tooth substance, and granular body almost absorbed.
Fig. 11. The cavity of reserve become a sac with a pulp, and further
removed from the surface of the gum. Temporary tooth pulp
covered with tooth substance, and granular body absorbed.
(See Hunter, Nat. Hist, of Human Teeth, p. 95.)
Fig. 12. The temporary tooth acquiring its fang by the triple
b
X EXPLANATION OF THE PLATES.
action described in the paper, and its sac approaching the
surface of the gum.
Fig. 1 3. The fang of the temporary tooth longer, and its sac touching
the mucous membrane of the mouth.
Fig. 14. The temporary tooth sac again a follicle ; free portion of
the latter becoming shorter, and fang of the tooth receding
from the bottom of its socket. Permanent tooth sac re-
moving further from the surface of the gum.
Fig. 15. The temporary tooth completed. Free portion of the sac be-
come the vascular border of the gum ; adherent portion
become what is commonly denominated the periosteum of
the fang, but which in fact is a triplex membrane viz.
mucous membrane, submucous tissue, and periosteum of al-
veolus or jaw bone. The permanent tooth sac much re-
moved from the gum, but connected with it by accord which
passes through the foramen behind the temporary alveolus.
Fig. 16. The fang of the permanent tooth lengthening, and the crown
approaching the gum Fang of temporary tooth undergoing
absorption.
Fig. 17. The same change more advanced.
Fig. 18. The permanent tooth appearing through the gum. Shedding
of the temporary tooth.
Fig. 19. The perfected permanent tooth.
Fig. 20. The shed temporary tooth.
d. Diagrams illustrative of the formation of the thrae molar teeth
from the non-adherent portion of the primitive dental groove.
Fig. 1 . The non-adherent portion of the primitive dental groove.
Fig. 2. The papilla and follicle of the first molar on the floor of
the non-adherent portion, which is now a portion of the
secondary groove.
Fig. 3. The papilla and follicle of the first molar become a pulp and
sac. The lips of the secondary grove adhering, so that the
latter has become the posterior or great cavity of reserve.
Fig. 4. The sac of the first molar increased in size, and advanced
along a curved path into the substance of the coronoid
process or maxillary tuberosity. The cavity of reserve
lengthened out or advanced along with it.
Fig. 5. The sac of the first molar returned by the same path to its
former position. The cavity of reserve again shortened.
Fig. 6. The cavity of reserve sending backwards the sac of the
second molar.
Fig. 7. The sac of the second molar advanced along a curved path
into the coronoid process or maxillary tuberosity. The
cavity of reserve lengthened for the second time.
Fig. 8. The sac of the second molar returned to the level of the
dental range. The cavity of reserve shortened for the
second time.
EXPLANATION OF THE PLATES. XI
Fig. 9. The cavity of reserve sending off the pulp and sac of
the wisdom tooth.
Fig. 10. The sac of the wisdom tooth advanced along a curved line
into the maxillary tuberosity or coronoid process.
Fig. 11. The sac of the wisdom tooth returned to the extremity of
the dental range.
MUSKET-BULLETS IN TUSKS OF ELEPHANTS.
PLATE II. page 56.
Fig. 1. A portion of a section of a wounded tusk ; a cement ; 5 regular
ivory deposited previous to the wound ; c irregular ivory
deposited after the wound.
Fig. 2. A diagram illustrative of the mode of connection between the
Retzian tubes of the primary and secondary regular ivory,
and the cells and Retzian tubes of the different inosculating
systems of the irregular ivory, after inclosure of a ball ; a
cement with its osseous corpuscles ; b primary regular ivory
with its Retzian tubes ; c the ball ; d the irregular ivory
with its systems of tubes and cells ; e secondary regular ivory
Fig. 3. A copper ball inclosed in a sphere of irregular ivory, on the
surface of which are the orifices of Haversian canals. Some
of the orifices have closed, and present the appearance of
irregular projections. The mass has begun to be attached to
the regular ivory of the tusk,, and would in time have been
inclosed in it. The ball must either have passed across from
the opposite side of the tusk, or must have sunk below the
level of the hole by which it entered.
Fig. 4. Section of a tusk across the cavity of which a ball has passed,
and become inclosed in the ivory of the wall opposite the
hole by which it entered. The hole is filled with irregular
ivory, coated externally with cement. The cement over the ball
has been disarranged by the shock. This section proves that
the track of a ball across the pulp is not necessarily ossified.
Fig. 5. Section of a tusk across the base of which a spear-head has
penetrated and remained in the wound. The weapon has
therefore been separated from the pulp by deposition of
irregular ivory in the form of a tube ; a cement ; b b ir-
regular ivory deposited previous to the wound ; c c regular
ivory deposited after the woimd ; d irregular ivory inclosing
a vacant space e, the seat of an abscess or sinus, and con-
tinuous with the cavity of /, a mass of irregular ivory (coated
with regular ivory) in the form of a tube surrounding the
foreign body. As irregular ivory always contracts in drying,
more than any other kind of dental substance, that portion
of the section marked g g has been bent outwards.
Fig. 6. The same section viewed in profile ; a the broken shaft of the
xii EXPLANATION OF THE PLATES.
spear ; 6 an irregular mass of cement formed round the orifice
of the wound by the membrane of the tusk follicle, and
which would have closed the wound had the weapon been
removed. The wound inflicted has in this instance, as in
many others, stunted the growth of the tusk at c c, so as
to render the part formed after the injury narrower and
weaker.
Fig. 7. A longitudinal section of a tusk in which a gun-shot wound
had terminated in abscess of the pulp ; a a cement ;
6 6 regular ivory deposited before the injury ; c c regular
ivory deposited after the injury ; d d irregular ivory bound-
ing the abscess ; e e masses of cement and irregular ivory at
the margin of the shot-hole.
Fig. 8. The external aspect of a portion of a tusk, which had been
transversely fractured ; a a the line of fracture united exter-
nally by irregular masses of cement.
Fig. 9. The internal aspect of the same portion of tusk ; a a the line of
fracture united by irregular ivory, a portion of which is
arranged in a reticular form. This reticular ivory is interest-
ing, as affording a natural analysis of the peculiar arrange-
ment of parts in the irregular ivory described in the paper.
Each bar of the reticular ivory is traversed longitudinally by
a medullary canal, from which radiate secondary canals and
Retzian tubes, the whole being coated with regular ivory.
This reticular ivory differs from the ordinary form of ossified
pulp, only in the greater distance between the Haversian or
medullary canals, so that portions of the pulp have remained
unossified between them.
DEVELOPMENT OF THE SUPRA-RENAL, THYMUS, AND
THYROID BODIES. PLATE III. page 66.
Fig. 1. A portion of an early embryo of the sheep.
a. Heart.
I. Lungs still in front of the intestinal tube.
c. Wolffian body.
d. Lateral mass of blastema, out of which is formed the supra-
renal capsule, thymus, and thyroid.
e. Cardinal vein.
/. Jugular vein.
g. Ductus Cuvieri.
Fig. 2. A portion of the early embryo of the sheep,
a. Intestinal tube and ductus vitelli.
6. Liver.
c. Omphalo-mesenteric vein.
d. Omphalo-mesenteric artery.
c, f. Mass of blastema on the inner side of the Wolffian body, and
EXPLANATION OF THE PLATES. xiii
around the trunks of the omphalo-mesenteric vessels ; this is
the posterior part of the lateral mass of blastema marked d
in Fig. 1, and becomes in the course of development the
supra-renal capsule.
Fig. 3. An early embryo of the sheep.
a. Head, branchial arches, and rudiment of the eye.
6. Heart.
c. Ductus Cuvieri entering the auricle, and receiving
d. The jugular, and
e. The cardinal vein.
/ The lateral blastema.
g. Wolffian body.
h. Umbilical cord, to which is passing
i. The allantois.
j. The omphalo-mesenteric artery, and
k. Omphalo-mesenteric vein ; traces of the umbilical vessels are
also seen in the parietes of the abdomen.
I. The liver and intestinal tube.
m. Lungs.
Fig. 4. Jugular veins and lateral masses of blastema in the sheep,
soon after the latter have joined across the middle line.
a. The triangular absorption of the cervical portion, which is
the first indication of the separation of the thyroid.
Fig. 5. The next stage, in which the thyroid is more distinct.
Fig. 6. The thyroid is now quite distinct, and differs from the thymus
in being opaque ; the latter exhibits opaque spots in a semi-
transparent matrix.
Fig. 7. The thyroid and thymus have assumed their perfect form.
Fig. 8. A portion of the supra-renal capsule of the adult green monkey,
slightly compressed. It exhibits the minute nucleated par-
ticles of which it consists. Among these, at pretty regular
distances, are seen the germinal spots.
Fig. 9. A portion of the thymus of the brown bear, slightly compressed.
It exhibits the nucleated particles of which it consists. These
are grouped in spherical masses around centres from which
they appear to have derived their origin.
Fig. 10. A portion of the thymus from a human foatus. It has been
taken from the surface of the gland, so as to exhibit the
areolar fibres which form its delicate capsule. The pressure
of the glass plates has almost obliterated the spherical
grouping in the cells.
Fig. 11. A portion of the membrane which covered the contiguous sur-
faces of the lobes of the thymus of a human foetus (the
membrane lining the reservoirs of Sir A. Cooper). It has
the same structure as in Fig. 10. It exhibits no germinal
membrane, but consists of an areolar or fibrous texture inter-
mixed with the cells of the organ, the fibres being more
XIV EXPLANATION OF THE PLATES.
fasciculated, and running a straighter course than in the
substance of the organ.
Fig. 1 2. A portion of the thyroid from a human foetus, slightly corn-
pressed. It exhibits the same structure as the thyinus, but
its fibrous texture is more developed.
Fig. 13. A portion of the same thyroid to show its vascular network, in
the meshes of which, as in Fig. 12, the cells are seen arranged
in groups.
CENTRES OF NUTRITION. PLATE IV. page 389.
Fig. 1. A portion of the middle and internal membranes of a large
encysted tumour situated under the tongue, and removed by
Professor Syme.
a. The middle or second membrane, which is a germinal
membrane, consisting of flattened cells, the lines of junction
of which are faintly visible, the nuclei remaining as the
germinal spots of the membrane.
b. The internal membrane, a layer of small cells, somewhat
spherical, with slightly granular contents.
The external membrane of the cyst, consisting of areolar
and elastic fibres, contained the blood-vessels of the morbid
growth.
The cyst contained a soft mass resembling thick honey
in consistence. The outer layer of this mass was white, and
consisted of large, flat, transparent cells or scales, with few or
no traces of nuclei. The larger internal part of the mass
was reddish-grey, and consisted of ovoidal cells, resembling
those of the external layer, except that they were turgid
with a transparent oily-like fluid, and contained nuclei in
various stages of development.
Fig. 2, a. Fig. 3, a. Cells of the meliceritous mass those without
nuclei being those of the white external layer, the others
belonging to the reddish-grey part of the mass, presenting
nuclei in various stages of development.
b b. Some of the latter cells, in which the nuclei have become so
much developed as to distend their cells beyond the average
size. In these enlarged cells, it will be remarked that the
nuclei, instead of remaining as single germinal spots for each
cell, have broken up into numerous spots or centres of
nutrition.
In a tumour of this kind, the cyst and its contents are
two distinct parts, and perform two distinct actions. The
cyst is the active agent in withdrawing materials of nutrition
for itself and its contents from the vessels which ramify in
its outer tunic. The organs which accomplish this are the
germinal spots in its middle tunic, which, in virtue of forces
EXPLANATION OF THE PLATES. XV
of attraction in each, select and remove from the capillary
vessels the matter necessary for the formation of the cells of
the internal layer. These after solution pass in succession
into the cavity of the cyst, to serve as nutriment for the
contained cellular mass.
This mass is evidently the principal element of the
morbid growth. The cyst is a subsidiary or accessory part,
arranged for the protection and due supply of nourishment
for its principal. The cells of which this mass consists have
each its own nucleus or germinal centre. These cells would
appear to be of two classes those whose nuclei produce
young cells in their interior for their own nutrition, but not
for the reproduction of new mother-cells, and those which
act as reproductive individuals for the whole morbid growth.
These latter cells are marked 6 6 in Figs. 2 and 3, and con-
tain numerous nutritive centres or germinal spots in their
interior. The flat cells of the white external layer appear to
be those individuals of the first class, which are about to
close their existence, their nuclei having disappeared ; their
food, therefore, no longer supplied to them, and their position
in the mass removed to the exterior by the eccentric
development of the younger and more active neighbouring
cells. In a morbid mass of this kind, as in the textures and
organs of an animal generally, certain parts are set aside as
reproducers, the remaining parts performing the functions of
the whole mass, texture, or organ ; just as in certain com-
munities of animals certain individuals are set aside to re-
produce the swarm, the others are devoted to the duties of
the hive.
Fig. 4. Two portions of the primary or germinal membrane from the
tubes of the tubular portion of the human kidney. The
germinal spots of the gland are seen imbedded in the sub-
stance of the membrane. The external layer of this mem"
brane, which may occasionally be seen with the nuclei
detached from it, is the basement or homogeneous membrane
of Mr. Bowman. In other instances, as when the epithelia
are but slightly developed, it becomes difficult to decide
whether we have merely the germinal membrane, or both
the membrane and its epithelia before us.
INTESTINAL VILLL PLATE IV. page 389.
Fig. 5. Extremity of a villus immediately before absorption of chyle
has commenced. It has cast off its protective epithelium,
and displays, when compressed, a network of peripheral
lacteals. The granular germs of the absorbing vesicles, as
yet undeveloped, are seen under its primary membrane.
XVI EXPLANATION OF THE PLATES.
Fig. 6. Extremity of a villus, with its absorbent vesicles distended with
chyle, and the trunks of its lacteals seen through its coats.
Fig. 7. Protective epithelium-cells from a villus in the dog.*
Fig. 8. Protective epithelium-cells cast off preparatory to absorption of
chyle ; instead of nuclei, they present, in their interior,
groups of globules.
Fig. 9. A group of the same cells adhering by their distal extremities.
Fig. 10. Secreting cells thrown out of the follicles of Lieberkiilin
during digestion.
Fig. 11. Diagram of mucous membrane of jejunum when absorption is
not going on. a. Protective epithelium of a villus. &.
Secreting epithelium of a follicle, c c c. Primary membrane,
with its germinal spots or nuclei, d d. e. Germs of absorbent
vesicles, f. Vessels and lacteals of villus.
Fig. 12. Diagram of mucous membrane during digestion and absorption
of chyle, a. A villus, turgid, erect ; its protective epithelia
cast off from its free extremity ;t its absorbent vesicles, its
lacteals and blood-vessels turgid. 5. A follicle discharging its
secreting epithelia.
PROCESS OF ULCERATION IN ARTICULAR CARTILAGE.
PLATE IV. page 389.
Fig. 13. a. A section of articular cartilage and absorbent membrane.
In the lower part of the section the cartilage - corpuscles
retain their natural size and appearance ; as they approach
the rugged ulcerated edge, they increase in size, and contain
numerous young cells, apparently the progeny of their nuclei ;
beyond this edge, rounded masses of cells, originally con-
tained within the cartilage-corpuscles, are seen embedded in
the cellular absorbent mass.
I. Absorbent cells of the false membrane, with two globular
masses derived from the cartilage-corpuscles.
SECRETING STRUCTURES. PLATES IV. V.
PLATE IV. page 389.
Fig. 14. Four secreting cells from the ink-bag of Loligo sagittata.
Fig. 1 5. Five cells from the liver of Patella vulgata. In this instance
the bile is contained in the cavities of the secondary cells,
which constitute the nucleus of the primary cell.
* It may be noted that both in figures. 7 and 9 the clear space at the broad free
ends of the columnar intestinal epithelial cells, to which several German anatomists
have recently directed attention, is figured by the author. EDS.
t The author subsequently abandoned the idea that the epithelial cells were
cast off during absorption. EDS.
EXPLANATION OF THE PLATES. XV 11
Fig. 16. Three cells from the kidney of Helix aspersa. The contained
secretion is dead white, and presents a chalky appearance.
Fig. 1 7. Two cells from the vesicles of the testicle of Squalus cornubicus.
The contained bundles of spermatozoa are developed from
the nucleus each spermatozoon being a spiral cell.
PLATE V. page 412.
Fig. 1. Five cells from the mamma of the bitch. In addition to their
nuclei, these cells contain milk-globules.
Fig. 2. A portion of duct from the testicle of Squalus cornubicus. A
few nucleated cells, the primary or germinal cells of the
future acini, are attached to its walls.
Fig. 3. The primary cell of an acinus in a more advanced stage. The
nucleus has produced a mass of young cells. The pedicle
appears to have been formed by the germinal cell carrying
forward the wall of the duct. A diaphragm accordingly
presents itself across the neck of the pedicle.
Fig. 4. A primary cell in a more advanced stage.
Fig. 5. A primary cell still more advanced.
Fig. 6. Some of the secondary cells, products of the nucleus of the
primary cell, are cylindrical, and are arranged in a spiral.
Fig. 7. The change into cylinders, and the spiral arrangement com-
pleted.
Fig. 8. a. One of the secondary cells ; its nucleus a mass of young cells.
6. A secondary cell elongated into a cylinder, each cell of its
composite nucleus elongated into a spiral, c. The spiral cells
or spermatozoa, free.
Fig. 9. A bunch of acini, in various states of development, maturity,
and atrophy.
The four following figures are diagrams, arranged so as to illus-
trate the intimate nature of the changes which occur in vesi-
cular glands when in a state of functional activity.
Fig. 10. A portion of gland-duct with two acini. One of the acini is
a simple primary cell ; the other is in a state of develop-
ment, its nucleus producing young cells.
Fig. 11. Both acini are advancing; the second has almost reached
maturity.
Fig. 12 The second acinus is ready to pour out its contents, the first
to take its place. ,
Fig. 1 3. The second acinus is in a state of atrophy, the first is ripe.
Fig. 14. Two follicles from the liver of Carcinus mcenas. The colour-
less germinal spot is at the blind extremity of the follicle.
The secreting cells become distended with bile and oil as
they recede from the germinal spot.
XV111 EXPLANATION OF THE PLATES.
THE STRUCTURE OF THE LYMPHATIC GLANDS.
PLATE V. page 412.
Fig. 15. A portion of the germinal membrane of tlie human, intra-
glandular lymphatics, with its germinal spots or nutritive
centres diffused over it.
Fig. 16. A portion of the same membrane, in which the component
flattened cells, with the centres, have been rendered trans-
parent, and are beginning to separate, by the action of acetic
acid. Five of the glandular epithelia adhere to the mem-
brane.
Fig. 1 7. A diagram of a lymphatic gland, showing the intra-glandular
network, and the transition from the scale-like epithelia of
the extra-glandular to the nucleated cells of the intra-
glandular lymphatics.
Fig. 18. A portion of an intra-glandular lymphatic, showing along one
edge the thickness of the germinal membrane, and upon it
the- thick layer of glandular epithelia.
THE STRUCTURE OF THE PLACENTA. PLATES V. VI.
PLATE V. page 412.
Fig. 19. The extremity of a placental villus.
a. The external membrane of the villus, the lining membrane
of the vascular system of the mother.
6. The external cells of the villus, cells of the central portion
of the placental decidua.
c c. Germinal centres of the external cells.
d. The space between the maternal and foetal portions of the
villus.
e. The internal membrane of the villus, the external membrane
of the chorion.
/. The internal cells of the villus, the cells of the chorion.
g. The loop of umbilical vessels.
Fig. 20. This drawing illustrates the same structures as the last, and
has beenlntroduced to show the large space which occasionally
intervenes between the internal membrane and the external
cells. It would appear that into this space the matter
separated from the maternal blood by the external cells of
the villus, is cast before being absorbed through the internal
membrane, by the internal cellfi. This space, therefore, is
the cavity of a secreting follicle, the external cells being the
secreting epithelia, and the maternal blood-vessel system the
capillaries of supply. This maternal portion of the villus,
and its cavity, correspond to the glandular cotyledons of the
ruminants, and the matter thrown into the cavity to the
milky secretion of these organs.
EXPLANATION OF THE PLATES. xix
Fig. 21. A portion of ike external membrane, with external cells of
the villus.
a. Cells seen through the membrane.
6. Cells seen from within the villus.
c. Cells seen in profile along the edge of the villus.
Fig. 22. The extremity of a villus treated with acetic acid. All the
parts are distinctly visible, and the germinal centres of the
internal cells are seen surrounding the umbilical vessel.
Fig. 23. A villus with a terminal decidual bar, along the cavity of
which the external cells are seen to be continued, so as to
pass forwards in the direction of the parietal decidua.
PLATE VI. page 445.
Fig. 1. A portion of the external membrane of a villus, with a lateral
decidual bar. This portion of membrane is seen from its
foetal aspect, and in this three or four germinal centres of
the external cells are perceptible.
Fig. 2. A drawing of the extremity of a villus treated with acetic acid.
In this villus all the parts described are distinctly seen, and
indicated by the same letters as in Fig. 19, Plate Y.
Fig. 3. The extremity of a villus, with a terminal decidual bar,
treated with acetic acid, to show the nuclei of the decidual
cells in the cavity of the bar, and on the external membrane
of the villus.
Fig. 4. Two tufts connected by a terminal decidual bar.
Fig. 5. A tuft with a lateral bar passing off from its stem.
Fig. 6. A diagram illustrating the arrangement of the placental
decidua.
a. Parietal decidua.
b. A venous sinus passing obliquely through it by a valvular
opening.
c. A curling artery passing in the same direction.
d. The lining membrane of the maternal vascular system,
passing in from the artery and vein lining the bag 'of the
placenta, and covering e e the foetal tufts, passing on to the
latter by two routes, first by their stems from the foetal side
of the cavity, and secondly by the terminal decidual bars f f
from the uterine side, and from one tuft to the other by the
lateral bar g. Throughout its whole course this membrane
is in contact with decidual cells, except along the stems of
the tufts, and the foetal side of the placenta, where the
decidual cells have degenerated into fibrous or areolar fibres.
All that portion of the decidua which is in connection with
the bars, villi, and tufts, is the central or functional portion
pf the decidua, and along with the lining membrane of the
maternal vascular system, or external membrane of the
tufts, constitutes the true maternal portion of the placenta.
XX EXPLANATION OF THE PLATES.
h. Two diagrams illustrating the foctaJ cellular elements of tlie
placenta! tufts. These are the internal membrane, and the in-
ternal cells of the tufts, and along with the loops of umbilical
blood-vessels constitute the true foetal portion of the placenta.
THE TESTIS AND ITS SECRETION IN THE DECAPODOUS
CRUSTACEANS. PLATES VII. VIII.
PLATE VII. page 429.
Fig. 1. Figures of Entozoa from the tubuli seminiferi of Orchestia
littoralis, probably allied to filaria, and supposed by M.
Kolliker to be the spermatozoa. This opinion, however,
is incorrect, as may be seen in the accompanying draw-
ings, where figures are given representing all the details
of the development of the true* spermatozoa. These are all
produced from cells, whereas the entozoa under considera-
tion are never seen within cells, but are in all cases generally
seen floating free in the seminal vessels. These filaria have
only been seen, so far as I am aware, in Amphipoda and
Isopoda. If they are spermatozoa, they must be produced
from cells ; and from what has been stated in the text, it
will be seen that in all the Crustacea, these cells, before pro-
ducing the spermatozoa, undergo several metamorphoses ;
and that the final changes take place in the spermatheca of
the female, where the seminal animalcules are produced. In
Amphipoda and Isopoda, where these supposed filaria exist,
we always find them high up in the testicle, and not occa-
sionally, but in great numbers. In the tertiary seminal cells
also, which are floating about among them, not the slightest
vestige of the worm can be observed. I am inclined to sup-
pose, therefore, that these thread-like worms, supposed by
Kolliker to be spermatozoa, are only parasites.
Fig. 2. Representation of a primary germinal cell projecting from the
wall of the seminal tube. It has just burst, and the young
secondary cells are escaping and descending the tube ; during
the descent they increase in size, from their nucleus throwing
off nucleoli, the latter forming the tertiary generation. In
this figure it will be observed that the cell-walls of the
parent are quite smooth and unbroken, so that in ail proba-
bility the young arise from that portion of the cell attached
to the seminal tube.
Fig. 3 Is a small quantity of the fluid from the spermatheca of the
female crab, showing the tertiary or spermatozoal cells after
they have burst from the secondary. As described in the
text, the spermatheca appears to be the organ in which the
seminal fluid undergoes the final and essential change which
fits it for impregnation.
EXPLANATION OF THE PLATES. xxi
Fig. 4. This figure shows the adult seminal secondary cells from the
dilated parts of the seminal tube. They are full of tertiary
cells. The fluid amongst which they are floating is thick
and albuminous, much more so than it is higher up or lower
down the tube, and the large, clear, transparent-looking
masses, are the pabulum for the nourishment of the cells
It is much more abundant in this part of the organ than any-
where else, and accordingly great numbers of the secondary
cells, in all stages of development, are constantly found here.
If a small quantity of the seminal fluid from that portion of
the testicle immediately preceding the dilated part be placed
under the microscope, it will be seen that the nuclei of the se-
condary cells are just throwing off small nucleoli, and that the
parent cell is not very much larger than when it burst from the
primary. In the same part also, little or no pabulum is ob-
served. As we proceed downwards, however, we find them
increasing rapidly in size ; and, at the same time, an immense
quantity of pabulum floating about in large masses. The
lower part of the tube and the vas deferens are almost desti-
tute of pabulum, the cells being satiated.
Fig. 5. The secondary cells of Hyas araneus from the vas deferens.
The walls of the parent cells are remarkably thin. The
parent secondary cells are of enormous size in this species.
Fig. 6 Represents the testicles of Carcinus mcenas, of the natural size,
and shortly before they have reached the maximum state of
development. The portion included between a a is the
tubular or hepatic, that between 6 b is the dilated or gastric.
The vasa deferentia are not seen in this species so well as in
Hyas araneus, Fig. 8, c c. It is in the gastric division that
the pabulum lies in such quantities.
Fig. 7 Is the internal or sheathed portion of the external organs of
Cancer pagurus ; proximal extremity.
Fig. 8. Testes of Hyas araneus. a a. Tubular portion. 6 &. Follicular
portion, c c. Vasa deferentia.
Fig. 9. External organs of Cancer Pacjurus. a. Is the internal or
sheathed portion in situ. b. Is the sheath or external portion.
Fig. 10. External organs of Hyas araneus. A. Sheath. B. Sheathed
portion.
PLATE VIII. page 431.
Fig. 1. First stage of development of secondary seminal cell of Gala-
thea strigosa.
Figs. 2, 3, 4. Second, third, and fourth stages of development of the
secondary cell.
Figs. 5, 6, 7, 8, 9, 10, 11, 12, 13. Various stages of development of
the secondary cell of lobster.
Figs. 14, 15, 16, 17. The same treated with acetic acid.
XX11 EXPLANATION OF THE PLATES.
Fig. 18. Tertiary or spermatozoal cells.
Fig. 1 9. Secondary cell of lobster seen from armed extremity, to show
the three setae.
Fig. 20. Primary cell, or caecum of testicle of Pagurus bernhardus full
of secondary cells, c. Attachment, b. Free extremity, a.
Nucleus.
Fig. 21. Primary seminal cell of Pagurus bernhardus filling with se-
condary cells. As already described, these cells grow in pairs
from discs on the walls of the seminal tubes, and hang free
in the cavity of. the tube. It has also been described how
the secondary cells are produced from the parent nucleus,
namely, by means of successive growths, each of which carries
off a fold of nucleus before it.
a. Disc from which the primary seminal cells grow.
b b. The discs on each side of it.
c c. The origins of the primary seminal cells.
d. One of the primary cells cut off.
e. Nucleus of the primary cell in a state of activity ; it has just
thrown off a series of young, marked
/. In the diagram.
g. Are several old walls of former growths.
h. Full extremity of primary cell.
Fig. 22. A small portion of the testicle of Pagurus bernhardus magni-
fied, showing the manner in which the caeca hang from the
walls of the seminal tube.
Fig. 23. Small drop of seminal fluid of lobster, showing the secondary
cells before the armature had expanded.
Fig. 24. Small drop of seminal fluid of lobster from vas deferens.
That part of the figure above a a, as seen under the micro-
scope, presents one dense mass of secondary cells floating
down towards &, where a few are seen separate.
Fig. 25. A caecum from the testicle of Carcinus mcenas, showing a ger-
minal spot at its apex just being filled, with secondary cells.
Fig. 26. The germinal spot enlarged.
REPRODUCTION OF LOST PARTS IN THE CRUSTACEA.
PLATES IX. XII.
PLATE IX. page 471.
Fig. 1 Represents the raw surface of the proximal or adherent portion
of the leg of Cancer pagurus, after the animal has thrown off
the distal portion. The figure represents the parts of the
natural size, and only a few hours after the separation had
taken place.
Fig. 2 Is a representation of the same part, after the young leg had
grown to some size. It will be observed that the cicatrix,
which was formed upon the raw surface a few hours after
EXPLANATION OF THE PLATES. xxill
separation, has now "become very strong, covers the young
germ, thus acting as a means of defence from external injury.
Figs. 3, 4, 5, Are the same parts in progressive states of development.
Fig. 5 presents a bifurcated character ; probably from some
accidental cause it thus appears smaller than it is in the
normal state.
Fig. 6 Eepresents the raw surface of the leg, already alluded to in
Carcinus mcenas, some time after separation. A nucleated
cell is seen in the centre. This drawing was made from a
very small specimen, and was only procured in the stage re-
presented after great difficulty.
Fig. 7 Represents a longitudinal section of a very young germ, for
the purpose of showing its mode of development. The fibrous-
looking band which surrounds it externally, is a circular canal
which belongs to a system of vessels described in the text.
The four striated bodies which lie next to this canal are the
rudiments of the four joints of the future limb. The striated
appearance arises from the muscles already so far developed,
and the albuminous matter within, and which they enclose,
appears to be pabulum for their farther nourishment. The
more defined globules, which may be observed floating
amongst the albumen, are oil-globules. In the development
of this leg, it will be observed that the external segments, or
those which are analogous to the thigh and first tibial joints,
are largest and most fully formed, a fact we would be led
to expect, from the circumstance of their formative cells being
the first thrown off from the original parent nucleus, and
consequently the first that would take on a central or more
independent action. From a similar mode of development,
we see that the second tibial and tarsal joints are the smallest,
as they are the last formed of the centres. The last or distal
phalanx is the smallest of the internal segments ; those
nearest the circular vessel are the largest, as was to be ex-
pected from the centres which formed them, being the oldest
and the first formed from the earlier generations of cells ; and
those again within them are smaller, being formed from the
later generations thrown off by the original parent.
Fig. 8. Cells from the external series represented by c in Fig. 9.
Fig. 9. Transverse section of raw surface of proximal or attached ex-
tremity of the reproductive organ in leg of Cancer pagurus.
This is the surface and appearance which is seen immediately
upon the leg falling off ; if it is seen half-an-hour, or a little
more, after the separation, it is covered with a thickish film,
which shortly becomes a strong opaque cicatrix hiding every-
thing beneath it. The vessels seen in Fig. 15 are also
omitted, for the purpose of showing the structure of the re-
productive body more clearly.
EXPLANATION OF THE PLATES.
a. Is the circular vessel, of the system of vessels mentioned in
the text, and it surrounds
6. A fluid or semi-fluid mass, containing small nucleated cells,
from which the germ is probably derived.
c. Is a large mass of very large cells surrounding the circular
vessel, which appear to act as a magazine of nutritive matter
for the young germ during its growth.
d. Is the shell membrane, which is surrounded externally by the
shell.
Fig. 10. A young limb of Carcinm mcenas still enclosed within its
original cyst, which is formed probably from the cicatrix
mentioned above. Magnified two diameters.
Fig. 11 Is a very young leg of the common lobster. The reproduced
leg of this species is not enclosed in a cyst, and it is not
folded upon itself, but projects straight forward. Nat. size.
Fig. 12 Is a figure of the natural size of one of the large claws of
Pagurus bernhardus, shortly after it has burst from its con-
taining cyst.
Fig. 13. Enlarged view of Fig. 11.
Fig. 1 4. One of the large claws of Carcinus mcenas still enclosed within
the cyst. From observations made, it appears that these
young legs remain within the cyst until their own covering
or shell is of sufficient strength to act as a means of defence.
They do not obtain a true shell for some time after the cyst
has burst.
Fig. 15. Raw surface of proximal extremity of leg in Cancer pagurus,
shortly after the animal has thrown off the distal portion.
This figure is made for the purpose of showing the distri-
bution of the peculiar vessels, and their mode of running
from the circumference towards the circular vessel in the
centre.
Fig. 1 6. Longitudinal section of young leg still within the cyst.
a. Part of old leg containing the reproductive organ. "
b. External cells.
c. Smaller nucleated cells.
d d. Cyst of young leg.
e. Femur of young leg.
/. First tibial joint of young leg.
g. Second tibial joint.
h. Tarsal joint.
Fig. 17. Natural size of young leg.
Fig. 18. Portion of blind extremity of one of the peculiar vessels which
are attached to the blood-vessel running to the leg, Plate XII.
Fig. 14. The contents are oil-globules, but in the figure
have somewhat the appearance of nucleated cells.
Fig. 19. An enlarged view, for the purpose of showing the connection
of these vessels.
EXPLANATION OF THE PLATES. XXV
Fig. 20. Two of the blind extremities from raw surface of leg, where
they present a clavate appearance.
Fig. 21. View of the extremity, showing the dark spot supposed to be
a germinal spot.
PLATE XII.
Fig. 9. Small longitudinal portion of shell from the large claw of
Cancer pagurus, showing the thickness of the annulus or
ring in it at the point of separation.
Fig. 1 2. Longitudinal section of one of the legs of Cancer pagurus,
showing the natural position and relations of the reproductive
organ.
a a. Femur.
6 6. Reproductive organ.
c. Natural appearance of line of separation
d. Coxa.
Fig. 1 3. Enlarged foramen as it is seen on raw surface after the separa-
tion. This has been hardened in boiling water, which gives
it a much more defined appearance, and also enlarges it more
than it naturally should be.
Fig. 14 Is a small portion of the femoral artery, about half-an-inch in
extent beyond the line of separation, which is covered as re-
presented by the peculiar vessels.
a. Distal extremity of blood-vessel.
ON THE ANATOMY AND DEVELOPMENT OF THE CYSTIC
ENTOZOA. PLATES VI. X. XL XII.
PLATE X. page 476.
Fig. 1. Magnified view of one of the young of Acephalocystis armatus
still attached to the germinal membrane of a secondary
parent. It is taken from the group shown in Fig. 2, and is
still in an early stage of development, the circlet of teeth
still being minute and not fully developed. The absorbing
series of cells may be seen internally.
Fig. 2. Small portion of the germinal membrane of a secondary parent
of Acephalocystis armatus highly magnified.
Fig. 3. Small portion of germinal membrane of Acephalocystis armatus
in a state of degeneration ; nothing is seen in the membrane,
which is quite homogeneous, except the small cells figured a.
6. Is the commencement of one of the cretaceous fatty masses
described in the text.
Fig. 4. Several of the stages of development of Cysticercus.
a. First stage represents spines ; hardly if at all seen.
b. Their first decided appearance.
c. Third stage.
XXVI EXPLANATION OF THE PLATES.
d. Fourth stage.
Fig. 5. Small portion of the germinal membrane of Acephalocystis
armatus.
Fig. 6. Small portion, highly magnified, of the granular matter from
the cyst of Cysticercus.
Fig. 7. Small portion of the inner surface of the external membrane
of Acephalocystis armatus while in a state of degeneration.
Fig. 8. Ovum from the pedicle of Cysticercus.
Fig. 9. Small portion of the germinal membrane of Acephalocystis
monroii, highly magnified.
a. Fibrous basis.
6. Germinal vesicles.
c. Secondary acephalocysts within the germinal vesicles ; this
portion was taken from the large parent cyst, which is the
primary animal, buried in the liver ; and each of the smaller
vesicles marked c belong therefore to the secondary genera-
tion, their progeny again being the tertiary generation.
Fig. 10 Is a specimen of Cysticercus neglectus ruptured at the fundus of
the sac, apparently for the escape of the young germs into
the cavity of the cyst, where they become attached.
Fig. II. Small portion of the cyst of Cysticercus neglectus magnified,
showing its vascularity, and the mode of attachment of the
young Cysticerci to its internal surface.
Fig. 12. View from above the pedicle of Cysticercus, showing the dis-
position of the teeth. In all works hitherto published on
Helminth ology, there has been a great want of proper figures
or descriptions of the true generic and specific characters of
these animals, a point of the utmost importance for obtaining
a proper knowledge of them : with this view the author has
paid scrupulous attention to the leading characters, and these
he has placed in the form of a synopsis at the end of the
chapter. All the drawings have been made with the view of
illustrating these characters more fully. The disposition of
the teeth, and their forms, are perhaps the most certain ex-
ternal characters.
PLATE XI. page 482.
Fig. 4. Magnified view of a small portion of the external or tubular
membrane of Diskostoma acephalocystis.
a. Larger disc.
b. Smaller one on its surface.
c. Tubuli.
d. Extremities of tubes.
e e. Gemmules, which at this stage of development may act as
absorbents.
Fig. 5. Natural size of Diskostoma acephalocystis.
Fig. 6. Diskostoma acephalocystis in various stages of development.
EXPLANATION OF THE PLATES.
a a a. Small cells arising from the attached surface of the tubular
membrane. This is the manner in which the original group
increases in size.
b. More advanced.
c. First stage of second mode of development, or that for the
extending of the parasite to as yet uninfested parts of the
body, for the purpose of forming new groups.
d. Second stage.
e. Third stage.
/. Root where the original germ became fixed.
g. External or tubular membrane.
Fig. 10. Section of Astoma acephalocystis, showing its internal structure
PLATE XII. page 487.
Fig. 1. Portion of sac of Cysticercus, much magnified.
a. Absorbing cells of absorbing membrane.
6 6. Separate ova, after their escape from the pedicle.
Fig. 2. Cysticercus neglectus very much magnified.
Fig. 3. Small portion of omentum containing Cysticercus neglectus,
showing the bodies considered to be young Cysticerci attached ;
the omentum has been folded over, and the young (a) are seen
attached to the fold.
Fig. 4. The natural size of the animal supposed to be a new Csenurus
Ccenurus hepaticus.
Fig. 5. Magnified view of the head of Acephalocystis armatus in a more
advanced stage than the former figure.
Fig. 6. The germinal membrane from which it was taken.
Fig. 7. The absorbing membrane of cyst of Cysticercus rattus highly
magnified.
Fig. 8. Teeth of Cysticercus rattus highly magnified.
Fig. 10. Ovum of Cysticercus rattus highly magnified.
Fig. 11. Ova from pedicle of Cysticercus rattus highly magnified.
PLATE VI. page 445.
Fig. 8. Gymnorhynchus horridus within its cyst.
Fig. 9. exposed.
Fig. 10. First stage of Ccenurus cerelralis.
Figs. 11, 12, 13, 14. Second, third, fourth, and fifth stages of the dis-
coidal period of development of Ccenurus cerebralis.
Fig. 1 5. One of the first stages in the vertical period of development.
Fig. 16. Sphairidion acephalocystis highly magnified.
Fig. 7. Neuronaia monroii. (J. Goodsir.)
a. Suctorial mouth.
6. Acetabulum.
c. Orifice of organs, supposed to be reproductive.
d. Posterior orifice, by which the sigmoidal "cistern a chyli"
e. Opens, and apparently also,
EXPLANATION OF THE PLATES.
/. The thick-walled peculiar sac.
g. Pyriform sac, a receptacle for the ova.
i. Male organs.
The figure also presents the arrangement of the dermal
spines, and the general form of the animal.
PLATE XL page 482.
Fig. 2. The anterior extremity and suctorial mouth of Neuronaia
monroii more highly magnified.
Fig. 7. The cyst of Neuronaia monroii in a bundle of nervous fila-
ments. The fissured appearance of the cyst, with its epithelia,
is represented in this drawing.
I am inclined to believe that the function of the cyst in
this and the other Cystic Entozoa is to supply nourishment
to the enclosed animal, drawing it from the surrounding
parts, and throwing it into the cavity, the structure and
action being identical with that in the encysted tumours as
already described.
The bulbous extremities of the cysts of Trichina spiralis
contain masses of germinating cells, to which I am inclined
to attribute the same function.
Figs. 8, 9, 11. The clavate extremities of the cysts of Trichina spiralis,
with their germinating absorbent cells.
The epithelium and absorbent cells of the cysts of the
entozoa may be considered as permanent yelk-cells in the
economy of these persistent embryos.
Figs. 1 and 3. Magnified drawingsj of Sarcina ventriculi described, but
badly figured by me in the Edinburgh Medical and Surgical
Journal, No. 151. I am still of opinion, notwithstanding
the arguments of Mr. Busk, in the Microscopical Journal, that
this body is a vegetable parasite, its sudden occurrence and
sudden disappearance being not more extraordinary than the
rapid development of many cellular structures ; the glandular
epithelium, for instance, during secretion. That it is a
Gonium, as has been suspected by Professor Link, appears to
me improbable, as would be admitted, I believe, by that
great botanist, if he had had an opportunity of observing its
peculiar vegetable aspect, so different from that of an in-
fusorial animal.
DIVISION I,
DEVELOPMENT AND MOKPHOLOGY.
VoUL
Plate L
DIVISION I.
I. ON THE OEIGIN AND DEVELOPMENT OF THE
PULPS AND SACS OF THE HUMAN TEETH.
PLATE I.
"II est peu de sujets en medecine sur lesquels on ait tant ecrit que sur les
dents ; deux cent volumes contiendraient a peine tout ce qu'on en a imprime !
Mais est-ce a dire que tout soit connu d cet egard ? Est-ce a dire que la
matiere ait ete epuisee et qu'il ne reste plus rien a faire? Nullement.
L'Anatomie n'a pas encore le dernier mot de la nature sur cet interessant
sujet et il reste encore, quoiqu'on en dise, quelques doutes a eclaircir et
plus d'une difficulte a resoudre." BLANDIN, Anat. du Systeme Dentaire, 1836.
SECTION I. EXAMINATIONS OF THE DENTAL ARCHES AT
DIFFERENT AGES.
1. An embryo (Fig. 1), which measured 7J lines from the
vertex to the point of the coccyx, weighed 15 grains,
and appeared to be about the sixth week,* was selected
and prepared for the purpose of examining the state
* It is difficult to determine the exact age of an embryo. The
ages given in the text, therefore, must be considered as approxi-
mations, being probably rather under-rated. I have given a full-sized sketch
of the youngest subject in which I have observed any of the phenomena of
dentition, with the weight and measurements of a few of the others. In
researches of this kind, the sequences of phenomena are of more importance
than their periods of appearance.
Velpeau, Embryologie ou Ovologie Humaine ; Breschet, Etudes Anatomi-
ques, etc., de I'oeuf dans Vcspece Humaine: Scemmering, Icones Embryonum
Humanorum.
B
2 ON THE ORIGIN AND DEVELOPMENT OF THE
of the palate and dental arches. The cheeks were divided
transversely from the commissures of the lips with fine scis-
sors ; the jaws were separated, removed, and fixed to the
bottom of a small capsule full of water. The point of the
tongue was removed. The configuration of the mouth was
then determined by means of a half-inch lens and two needles,
bent at the points, and fixed in slender handles.
Upper Jaw. The roof of the mouth was bounded an-
teriorly and laterally by the free edge of the lip (a, Fig. 2),
which is at this age thin and of great transverse extent.
Within the lip (a\ but separated from it by a groove (6),
to be more particularly described afterwards, there was
observed a lobe of a horse-shoe shape (c), narrow anteriorly at
the median line, broader, flatter, and of a rounded form on
each side posteriorly. Coming out from above the internal
posterior edges of this lobe (c), and
firmly adhering to it, two other
lobes (d d) were seen ; flat, rounded,
and curving backwards and in-
wards posteriorly, gradually dis-
appearing by pointed extremities
anteriorly. From the posterior extremities of each of the
lobes now described (d d), and of the horse-shoe lobe (c),
a thin semitransparent membranous fold (e e) passed back-
ward on each side, attached externally to the sides of the
capacious bucco-pharyngeal cavity, bounded internally by a
free edge opposed to its fellow of the opposite side, and
terminating posteriorly on the lateral walls of the pharynx.
Adhering to the inferior surface of each of these folds was
seen a smaller lobe (//) somewhat similar to the two last,
and situated a little behind them. The needle placed under
the folds showed that they were free and floating, except at
their exterior or adherent edges, and that they constituted a
partial division of the large common nasal, buccal, and pharyn-
PULPS AND SACS OF THE HUMAN TEETH. 3
geal cavity into a superior and an inferior compartment. The
upper wall of this common cavity was smooth and flat pos-
teriorly (g) ; but anteriorly it was contracted and terminated
in a longitudinal bar (Ji), which ran forwards to be attached
to the superior surface of the horse-shoe lobe at the median
line, and to the other parts in that neighbourhood. Under
the bar Qi) a deep cavity (i i) was seen, which communicated
with the exterior of the face by two small foramina, which
constituted at this period the whole external nasal organ. As
before-mentioned, a groove (&) was observed between the lip
(a) and the external edge of the horse-shoe lobe (c). This
groove (b) was deep, and its walls and lips were in close
apposition. It terminated posteriorly on each side (k Jc) by
becoming more shallow, and curving backwards and inwards
on the inferior surface of the membranous folds (e e). There
was a median frenum between the lip and the horse-shoe
lobe.
Lower Jaw. The under lip (a, Fig. 3), resembled the upper,
and was separated along its whole
extent by a groove () similar to
the one above, from a semicir-
cular lobe (c). Anteriorly this
lobe (e) was divided into two
median large (d d), and two la-
teral smaller lobules (e e), the whole being firmly adherent
to the floor of the mouth in front of the tongue and its
frenum, which were both well developed. The lateral parts
of the lobe (c) were rather indistinct, but at the point where
the free edge of the lip terminated, it extended transversely
and posteriorly, became thick and bulbous (//), and exhibited
on its surface a narrow shallow groove of a sigmoidal form (g g),
which was continuous with the groove behind the lip. There
was a median labial frenum.
On the external sides of the membranous folds in the
4 ON THE ORIGIN AND DEVELOPMENT OF THE
upper, and of the posterior parts of the lobe in the lower jaw,
the cut surfaces of the cheeks made by the scissors were seen
(I l t 1 1).
The mucous membrane over its whole extent was thin, and
of a greyish-yellow colour, the lobes granular, very friable, and
of a dead white. The breadth of the upper alveolar arch was
14 line, and the length of the same was 1 line.
2. The jaws of an embryo which measured 1 inch, weighed
20 grains, and appeared to be about the seventh week, were
prepared and examined as in the former case.
Upper Jaw. The free edge of the lip (a, Fig. 4) was not
so extended as at the sixth week.
The horse-shoe lobe (c) had become
broader and more developed pos-
teriorly, and anteriorly exhibited
three lobules, one median (m), and
two lateral. and anterior (n n). The
two lobes observed on each side of
the palate in the former embryo (d
d, f /, Fig. 2), had disappeared, hav-
ing apparently coalesced ; the posterior one (/) being curved
forwards to join the anterior (d), in the point (s t Fig. 4), while
the combined mass had contracted itself towards the front
of the mouth within the limits of the horse-shoe lobe (c).
The cleft had slightly diminished, but was still of sufficient
width to display the whole of the undivided nasal cavity.
The lip (a) was so lax as to admit of being moved by the
middle. The horse-shoe lobe (c) could also be pressed by the
same means inwards and backwards. When these two parts
were separated, the mucous membrane was seen to form a
duplicature (&), between the lips and a ridge (0), which ex-
tended from the posterior part of the dental arch to the outer
extremity of the lateral lobule (n).
PULPS AND SACS OF THE HUMAN TEETH. 5
The median portion of the dental arch was formed by
the two lateral lobules (n n) 9 which separated the lips from
the median lobule (m), and extended also a little on each side
of it.
The lateral portions of the arch presented externally the
ridge (o), formerly mentioned, smooth and convex on its exter-
nal surface, internally moulded into three curves, the anterior
long and shallow, the second deeper, the third or posterior
almost semicircular. Behind the last curve, the internal edge
of the ridge formed a deep notch, which swept outward and
forward, so as to mould the former into an almost isolated
lobule (<?). The ridge now disappeared, but its edge continued
backwards and inwards, winding around the posterior extremity
of the horse-shoe lobe (c), so as to form a groove (k k, Figs. 2
and 4), on the surface of the soft mucous membrane. The in-
ternal division of the lateral parts of the dental arch was
formed by three bulgings, apparently productions from the
horse-shoe lobe (c), and which were separated from the curves
of the ridge (o), by a groove which was deeper at their sides
than in their intervals. The anterior one was lengthened and
indistinct, the middle one was more developed, the posterior
circular, convex, and altogether isolated. The isolation of this
bulging was produced by a longitudinal lobule (r), apparently
cut off from the external edge of the horse-shoe lobe (c), and
forming a partial inner ridge corresponding with the outer
one. This new lobule (r) reached back
as far as the posterior extremity of the
horse-shoe lobe (c), and terminated an-
teriorly near the middle of the centre
bulging.
Lower Jaw. In the situation of the a ' ;!> ^
dental arch, there existed a groove (h, Fig - 5 -
Fig. 5), very distinct posteriorly, but having no outer lip an-
teriorly. The inner lip (m), presented posteriorly a large lobe
ON THE ORIGIN AND DEVELOPMENT OF THE
(n), under which the needle was easily inserted for a short
distance. In the middle, this lip (m) was thin, elevated, and
curved over the groove (h). Anteriorly it became broader,
and curved still more over the groove, and was divided into
two median larger lobules (d) y and two lateral smaller (e).
Between the two median (d) there was a notch at the attach-
ment of the lingual frenum. The outer lip (/) was defi-
cient anteriorly, so that the groove was bounded in that
situation by the under lip (a), which was loose, free, and
turned outwards. Posteriorly the outer lip (/) was well de-
veloped, and came out from under the posterior lobe (n) of the
inner lip, so as to render the grove (h) pointed, and curved
backwards and inwards. This lip (/) extended only about
half-way towards the median line, and appeared flat, or in the
same continuous plane with the floor of the groove. It was
also curved outwards, so as to overhang the labial mucous
membrane.
The groove presented an elevation (o) of its floor near its
posterior extremity. There was a labial frenum. The mucous
membrane possessed the same physical properties as at the
sixth week. The lobes were not so granular, but tougher and
more consistent. Breadth of superior arch 1 J line, length 1.
3. The jaws of an embryo at the second month, having
/% been prepared in the usual man-
ner, presented the following ap-
pearances :
Upper Jaw. The lip (a, Fig.
6) was more movable, and its free
edge less extended. The cleft in
the palate had diminished, exist-
ing only as a small angular defi-
ciency (x) in the pendulous por-
tion. The horse-shoe lobe was still perceptible under the
PULPS AND SACS OF THE HUMAN TEETH. 7
form of a bulging (c), represented as turned aside to ex-
hibit the objects under it. The lobule (r) had increased
in size, so as to extend further backwards, and to appear
on the posterior lateral parts of the palate. The median
lobule (m) had become triangular, the anterior edge being
formed by the curve of the palate somewhat pointed in front,
the lateral edges being straight and meeting in an angle
behind, from which the median line of suture or raphe of the
palate proceeded. The median lobule (m) had increased re-
latively, the lateral lobules (n ri) only absolutely. The
posterior portion of the dental groove (&) was longer, wider,
and not so much curved.
The bulging or papilla (1) was more distinctly isolated ;
and at the anterior extremity of the second curve in the ridge
(0), another papilla (2) had appeared as a production from the
latter. This papilla (2) was bounded externally by a lamina
(p\ which was also a production from the edge of the ridge
(o\ and was notched at its inner margin, where it was applied
to the side of the papilla.
The dental groove then terminated in a point, at the outer
extremity of the lateral lobule (ri). There was a labial frenum.
Lower Jaw. The posterior portion of the dental groove
had undergone no material change,
but had become deeper, and con-
tained in the situation of the ele-
vation marked (o, Fig. 5), a distinct ' ~~~
rounded papilla (1, Fig. 7). Fur-
ther on, another papilla (2) bounded
externally by a notched lamina (a)
had appeared. This combined papilla and lamina was
exactly similar in its configuration and relations to that
marked (2, Fig. 6). The anterior part of the groove
had become more distinct, not because it had acquired an
outer lip, but because its floor had risen above the level
8
ON THE ORIGIN AND DEVELOPMENT OF THE
of the labial mucous membrane. There was a labial frenum.
The breadth of the superior arch was If line ; length li.
4. The jaws of an embryo nine weeks old were examined
under water.
Upper Jaw. No material change had taken place in the
configuration of the palate, except that
the median lobule (ra, Fig. 8), had di-
minished relatively, and in the trans-
verse direction, while the lateral
lobules (n) had increased relatively,
and also in the transverse direction.
A longitudinal lobule (y), had also
appeared on the surface of the
median lobule (m). The cleft
(x) in the soft palate was smaller.
The posterior part of the dental groove was wider. The
papilla (1), had become more prominent, and the lips of
the groove had almost met before and behind it. The papilla
(2) is larger. A little further on, corresponding with the
lateral lobule (n\ on each side, two papillae (3 and 4), with
notched laminse in front of them, had appeared. The centrals
(3), or those on each side of the median line, were the
most distinct.
Lower Jaw. The lips of the dental groove had approached
so as to require separation by the
needle to exhibit its contents dis-
tinctly. The papilla (1 or 2, Fig. 9)
had undergone little change, but two
very indistinct bulgings (3 and 4)
had appeared on each side of the
labial frenum, the centrals (3) being the Fig. 9.
largest. The breadth of the superior arch was If line ; the
length 1-J line.
PULPS AND SACS OF THE HUMAN TEETH.
9
Fig. 10.
5. In an embryo of the tenth week the following ap-
pearances presented themselves :
Upper Jaw. Very little change had taken place in the
lateral lobules (n, Fig. 10), or
the median (m) and its additional
lobule (y). They had all increased
absolutely, and if any relative change
had taken place, it was in the trans- .
verse diminution of the median (m)
and the movement forward of its
additional lobule (y). The palate
had advanced anteriorly, so as not
only to have encroached in some de-
gree upon the median and lateral lobule, but also to have
thrown itself into folds immediately behind them. The outline
of the horse-shoe lobe (which is represented in the sketch as
turned aside to exhibit the dental groove), was still observed.
There was an indistinct uvula. The papillae (1 and 2) had
sunk completely into follicles, and could only be seen by
looking into the open mouths of the latter. The mouth of
(1) was bordered by four laminae or lids, that of (2), by three,
as represented in the sketch. The papillae (3 and 4) had not
increased much, but their notched laminae had become more
distinct. At the posterior extremity of the
floor of the dental groove, on the inner side
of the lobule (q, Figs. 4, 6, 8, 10), a slight
bulging (5, Fig. 10) was seen.
The upper lip had receded in the neigh-
bourhood of the median line, so as to have
U disappeared almost entirely at that spot,
the centre of the upper dental arch being
Fig. n. exposed.
Lotver Jaw. The bulgings on each side of the median line
(3, 4, Fig. 11), which were so indistinct in the last subject,
10 ON THE ORIGIN AND DEVELOPMENT OF THE
had become well developed and inclosed in follicles, through
the mouths of which they were seen. A similar change
was observed in reference to the papilla (2). The follicles
had been produced by the stretching across of productions
from the outer lip (which was very indistinct) towards
similar but much smaller productions from the inner lip
(which was still very prominent). The lines of junction
of the septa were visible, and the mouths of the follicles pre-
sented an unfinished appearance. The papilla (1) had become
surrounded by an incomplete follicle, in consequence of the
production of a notched lamina from the outer lip of the
groove, which lamina was almost met by a smaller slip of
membrane from the inner lip. The breadth of the superior
arch was 2 lines, length II line.
6. IWi or 12^ week. Upper Jaw. The median lobule
(m, Fig. 12) had diminished so much
transversely, as to have become an-
tero-posterior ; while its supplement-
ary lobule had become attached to the
frenum of the lip. The lateral lobules
(n) had increased much transversely,
and appeared each to be divided into
an anterior and a posterior portion. They were compressed
by the true palate, which was folded at this part, as at
the tenth week, into wrinkles, the longest and anterior
of which stretched across the median line from the right
to the left side. The papillas (3 and 4), with their fol-
licles, were fully developed. The other two papillae (1 and
2, Fig. 10) had not undergone much change, but the small
bulging (5, Fig. 10) had now become a distinct papilla, and
its follicle had begun to show itself. The uvula was well
marked.
Lower Jaw. The lines of junction of the interfollicular
PULPS AND SACS OF THE HUMAN TEETH. 11
septa had almost disappeared, and the mouths of the follicles
had become more distinct. The mouths
of the three anterior follicles had an an-
terior lip, the free edge of which was
directed somewhat inwards. It was ne-
cessary to lift up this lip with the needle
to obtain a view of the contained papilla.
At the posterior part of the dental groove,
another papilla with a notched lamina,
both productions from the external lip, had appeared (5, Fig.
13). Breadth of superior arch 12i lines ; length, 2.
7. I3th week. Upper Jaw. There was little change in
the configuration of the palate since the former week. The
lobe running across the median line was still visible. The
frenum of the upper lip had become closely attached to, and
continuous with, the median lobule. The outlines of the
horse-shoe lobe were still perceptible, and on its external side
the lobule, all along marked (r), was visible. The outer lip of
the dental groove, or the external alveolar process, was equally
developed all around. The upper lip was still much retracted.
There were ten papillae inclosed in open-mouthed follicles, and
ranged at nearly equal distances all around the dental groove.*
The four anterior papillse were flattened from before back-
wards with a straight edge, and were somewhat similar to
the future incisive teeth. The next one on each side was a
simple cone. The two posterior on each side were also
conical, but flattened transversely, so as considerably to
resemble carnivorous molars. Each of these papillae ad-
hered by its base to the fundus, while its apex, as during
the eleventh and twelfth weeks, presented itself at, or, as
in the present instance, protruded from, the mouth of its
* Arnold, Salzburg Med.-CMrurg. Zeitung, 1831, Erster Band, p. 236.
Valentin, Handbuch der EntivicJcelungs-geschichtc des Mcnschen, p. 482.
12 ON THE ORIGIN AND DEVELOPMENT OF THE
follicle. The point of the needle could be introduced through
the mouth, so as to move the papilla about in the interior of
the follicle.
By removing the outer lip of the dental groove, and the
outer wall of all the follicles by the scissors, a good view was
obtained of the configuration of these
parts (Fig. 14). The follicles were
" Y V V observed to be mere duplications of
the membrane of the groove, and
consequently of the general gastro-intestinal mucous membrane.
The inner surface of the follicles was of a greyish-yellow
colour. The papillae had increased relatively so as to protrude
from the mouths of their follicles. They were granular, friable,
and of a dead- white colour.
Lower Jaw. No remarkable change had taken place in
the lower jaw, except in the relative enlargement of the papillae,
and in the distinct development of the follicle of the posterior
papilla (5, Fig. 13). The outer lip of the dental groove was not
very distinctly marked, but the inner was well developed.
The breadth of the superior arch was 3 lines, and the length
was also 3 lines.
8. 14th week Upper Jaw. The median lobule had
undergone little change, the lateral lobules had become
broader from before backwards, apparently in consequence, of
the retraction of the palate, which, instead of exhibiting on
its anterior part the confused transverse wrinkles formerly
mentioned, presented on its lateral divisions (corresponding
to the horse-shoe lobe) four or five parallel rugae, which were
apparently remains of the wrinkles. The upper lip had
again become full, so that its free edge was on a level with
the surface of the palate. The soft outer edges of the palate
and the anterior edges of the lateral lobules were now closely
applied to the outer lip of the dental groove, so as to close the
PULPS AND SACS OF THE HUMAN TEETH. 13
latter in a valvular manner. When these edges viz. the
continuous semicircular outline of the whole palate were
raised by the needle, the dental groove and its contents
viz. ten papillae in their follicles were seen. It was observed
that the follicles had increased relatively, the papilla only
absolutely, in consequence of which the latter, instead of pro-
jecting from, had receded within, the mouths of the former.
The mouths of the follicles had apparently become smaller.
This had arisen in consequence of the greater development of
the laminae which were seen in the earlier
3
stages. There were two, an anterior and a
posterior, for the four anterior follicles ; three,
an internal and two external for the third on
each side ; and four for the two posterior on
each side (Fig. 15). Close upon the inner /
side of the mouth of each of the follicles fl
there was observed a little depression in the w/
form of a crescent, its concave edge being to-
wards the former. These depressions were most distinctly
marked at the four or six anterior follicles, where they
were situated immediately behind their inner lips (a a a
a a).
Lower Jaw. The papilla had receded. The laminae of
the follicles were more developed (Fig. 16).
Little depressions or lunulae had appeared
similar to those in the upper jaw. When
the membrane of the dental groove with
its adherent follicles and their pulps,
was stripped off, the dental nerves and vessels were found
running along under the follicles, and distributing vascular
branches and a nervous twig to each of them (Fig. 14).
Each of the individual follicles, with its papilla, vascular
branches, and nervous twig, exactly resembled a large hair-
bulb with its nerve and vessels exposed after the hair has
14
ON THE ORIGIN AND DEVELOPMENT OF THE
been extracted. Breadth of the superior arch, 3i lines ;
length, 3 lines.
9. 15th week Upper Jaw. The outer edges of the
palate, which in the last embryo lay unattached on the outer
lip of the dental groove, in the present subject adhered firmly
to it, except along a small portion posteriorly (a, Fig. 17).
This adhesion was firm anteriorly on
both sides of the median line, then
became weaker, and posteriorly at
the non-adherent portion (a\ be-
tween the lobules (r and t\ the lips
of the groove retained their original
smooth edges. When the lips of this
non-adherent portion were separated
by the needles, its floor and walls exhibited nothing but the
greyish-yellow mucous membrane of the original groove. The
outer lip of the dental groove was visible all around the ex-
ternal margin of the palate, and was divided on both sides
into three parts, an anterior (u\ a lateral (o), and a posterior
(). On the inner side of the latter was seen the longitudinal
lobule, which has hitherto been marked (r). The median
lobule (m) was rounded anteriorly, and had a process (?/, Figs.
8 and 10), which stretched forwards between the lobules (u u).
This was the additional lobule formerly mentioned. The sides
of the median lobule were straight and converged to its pos-
terior extremity, which was circular, and was received into
a curve in the middle of a transverse band, constituting the
anterior boundary of the palate, which appeared to have re-
ceded still more than in the last subject, and to have exposed
still more completely the lateral lobules (n n). The four rugse
seen in the last subject had become ridges beautifully crenated,
and converging, as represented in the sketch, towards a curve,
reversed and opposite to the one formerly mentioned in the
PULPS AND SACS OF THE HUMAN TEETH. 15
middle of the transverse band of the palate. This last curve
was the result of the anterior junction of the lobes (d d } Fig. 2),
and was traced through all its phases to its present state.
The median suture of the palate proceeded from it posteriorly.
The dental groove being torn open by means of the needles,
its lips were found to have adhered pretty firmly, as before
mentioned, but a feeble adhesion only had taken place between
its walls so as to allow its contents to be restored to their
original condition by means of a blunt instrument. This was
carefully done under water, and the mouths of all the follicles
with their laminse were displayed. The latter were more
developed than in the last subject, and completely concealed
the papilla. The former required to be lifted up in order to
display the latter. Careful observation during the separation
of the contents of the groove disclosed the important fact that
the general adhesion had not obliterated the little crescent-
shaped depressions behind the mouths of the follicles. These
retained the smooth greyish-yellow colour of the walls of the
original groove, and from this circumstance could be distin-
guished from the general flocculent appearance of the other
parts.
Lower Jaw. The outer lip of the dental groove had in-
creased in size, and was as prominent as the inner, except
posteriorly, where the latter still retained its posterior lobe ;
but the most remarkable change which
had taken place since last week was
the complete adhesion of both lips, as
in the upper jaw, with the exception of
a small portion posteriorly, which still
retained the peculiar appearance of the
dental groove, and in which nothing could
be seen but the smooth mucous membrane ( , Fig. 18 ).
When the dental groove was torn open, as was done in the
upper jaw, the laminse (which were highly developed) of the
16 ON THE ORIGIN AND DEVELOPMENT OF THE
follicles, and the walls of the groove, were found to be rough
and flocculent from adhesions, with the exception of the little
depressions formerly mentioned, which still retained their ori-
ginal appearance.
Breadth of the superior arch, 5 lines ; length, 4 lines.
10. Wth week. Upper Jaw. The palate retained the
appearance it had in the last subject, with the exception of
the median lobule, which had become narrow in front, and
broad posteriorly. The raphe of the dental groove had become
firmer, so as to give a much more defined and permanent ap-
pearance to the non-adherent portion posteriorly, which was
now seen to great advantage, its fine greyish mucous mem-
brane gradually running at its edges into the white tough
substance of the palate and gums.
Having separated the lips of the non-adherent portion
(a, Fig. 19), a papilla, sunk in an open fol-
licle, with three or four laminae, was visible
(6). The membrane of the palate and max-
illary arch being stripped from the bone, and
its surface of adhesion examined, lines cor-
responding with the .sutures of the bones were observed ; one
the median, another the intermaxillary, and a third with the
palato-maxillary. Five tooth-sacs were also observed on both
sides of the maxillary arch. These were divided into three
groups, two in the first or anterior, one in the second, and two
in the third or posterior. These groups were covered with a
flocculent spongy membrane, which was easily stripped off by
the forceps, and when this was carefully done, it became evident
that the sacs which were formerly grouped together by this
membrane were individually isolated, and formed of a thin
grey diaphanous membrane, similar to the one formerly men-
tioned as covering the bottom of the dental groove, and con-
stituting the membrane of the follicles. The careful detach-
PULPS AND SACS OF THE HUMAN TEETH. 17
ment of the external spongy membrane from the posterior
group showed, what was not at first observed, that there was
at the posterior part of the posterior sac another very small
one, which by careful examination was seen to be the fundus
of the open follicle in the non-adherent portion of the dental
groove.
The adhesion of the lip and walls of the groove had now
become so strong, that it was impossible to separate them.
The only way, therefore, in which its contents could be
examined was by transverse sections. When these sections
were made between the different sacs, they displayed scarcely
any traces of the dental groove ; but when they passed through
any place perpendicular to the surface of the gum, and near to
the middle of any of the sacs, they exhibited the appearances
represented in the marginal sketch (Fig. 20). The deciduous
tooth pulp (a), which was lately a free pa-
pilla ; (6), the section of its sac, which was
a follicle when the pulp was a papilla ; (d),
the line of adhesion of part of the walls
of the dental groove leading from the shut
sac to (c), the raphe of the groove ; (e), the section of the
non-adherent portion of the groove in the situation of
the lunula, which existed behind (/), the inner laminae
of the sac (&), in its former follicular condition. From the
consideration of this section (Fig. 20), the mode in which
the original follicle, the non-adherent depression behind
the inner laminae, and the walls of the dental groove, were
connected after full adhesion of all the neighbouring parts,
will be easily understood. The little cavity (e) adhered by
its anterior and inferior extremity to the line of adhesion
(d) t so that it and the sac of the milk-tooth were both con-
nected to the raphe of the edges of the dental grooves by lines
of attachment, which resembled two petioles proceeding from
a common footstalk. These lines of attachment were not
18 ON THE ORIGIN AND DEVELOPMENT OF THE
tubular, but resisted all efforts to push a fine probe or bristle
through them ; they were merely opaque remains of the sur-
faces of junction contrasting with the semitransparent
substance of the gums. Parallel sections through all the sacs
exhibited similar appearances. When the contents of the sacs
were examined, the pulps were found to have acquired the
configuration of the bodies of the future teeth. The bases by
which the molar pulps formerly adhered to the bottoms of
their sacs, and which may be denominated their primary bases,
had become almost divided into three secondary bases, which
corresponded with the internal and two external fangs of the
future teeth. This division was so far accomplished by the
advancement of the internal grey membrane of the sac, under
the form of small compressed canals between the base of the
pulp and the external spongy membrane. These canals, which
were three in number, one external and two internal, did not
meet in the middle under the pulp. Deposition of tooth-sub-
stance (Zahn-substanz) had commenced on the edges and
tubercles.
The sacs were twice as large as their contained pulps, and
in the space (g, Fig. 20), which existed between them, there
was observed a very soft flocculent gelatinous substance, which
had no attachment to the pulp, and did not appear to adhere
to any part of the sacs, except the laminae and the parts ad-
joining them.
Lower Jaw. The adhesion of the dental groove was not
so strong as in the upper jaw. The open portion (a, Fig. 18),
was fully defined, and exhibited on its floor the orifice of a
follicle, containing a papilla. In other respects the lower was
similar to the upper jaw.
Breadth of superior arch 7 lines ; length 5 lines.
11. 5th month. Foetus minutely injected with size and
vermilion.
PULPS AND SACS OF THE HUMAN TEETH. 19
Upper Jaw. The lobes (t, o, u, Fig. 21) had become
highly developed. The anterior one
(u) was convex anteriorly, with a
sharp edge directed backwards, and
corresponded with the incisive teeth.
The central lobe (o) had become
shorter, but more prominent, like a
canine tooth. The posterior (t) had
united firmly with the longitudinal
lobe all along marked (r), so as to
close the open portion of the groove (a, Fig. 17), which
was described in the two last subjects. The raphe of the
groove between these two lobes w T as serrated, and a vessel
was seen traversing each denticulation. The raphe then ran
close along the inner edges of the bases of the lobes (o and
u). The median lobule was triangular, the base posterior ; the
apex in front continuous with the labial frenum, and situated
between the anterior pointed extremities of the lobules, (u, u).
The lateral lobules were very distinct. The other less im-
portant changes which had taken place in the palate may be
understood by comparing Figs. 21 and 17.
The membrane of the palate, with the sacs of the teeth,
was removed from the bone. The fundus of the follicle (6,
Fig. 19), had now assumed the appearance of a sac, and the
other ten, instead of being grouped, had become isolated.
The branch of the dental artery, which supplied each of the
sacs and their pulps, was seen, when it reached the fundus of
the former, to give off a number of twigs, which, radiating
from their common centre, proceeded perpendicularly towards
the gum, near which they inosculated with others proceeding
from it. The combined vessels then formed a pretty minute
network in the spongy membrane formerly described.
Transverse sections were now made by the scissors through
all the sacs. The general appearance of. these sections was
20 ON THE OHIGIN AND DEVELOPMENT OF THE
similar to that of those at the fourth month ; but the gelatinous
granular substance between the pulp and the sac was of the
consistence of very firm jelly, closely and intimately adherent
to the whole interior of the sac, with the exception of a narrow
strip all round the base of the pulp, along which strip the
grey membrane of the sac retained its original appearance,
and through which the radiating saccular twigs were visible,
being strongly and beautifully contrasted with the cream-
coloured surface of the granular substance. The mass of the
granular substance had a peciiliar greyish-white colour ; its
surface was cream-coloured, and had a dry chalky appearance.
It had a tendency to tear in a direction perpendicular to the
internal surface of the sac. Although closely applied, it did
not adhere to the pulp, but, as stated above, surrounded it on
all sides till within a short distance of its base " whatever
eminences or cavities the one had, the other had the same,
but reversed, so that they were moulded exactly to each other."
In the incisives its principal mass lay " against the hollowed
inside of the tooth, and in the molars it was placed directly
against their base like a tooth of the opposite jaw." In the
pulps of the molars, which had three canals which now passed
completely across their bases, the granular substance sent a
process into each of them. These processes did not meet in
the centre, but disappeared near to it, and left, as in the case
of the general mass, a minute portion of the grey membrane
of the sac between themselves and the secondary bases of the
pulp.* In the case of the molars also the dental arterial
* The only authors, as far as I know, who have observed and described
this gelatinous body, are Mr. Hunter in his Natural History of the Teeth, p. 94,
and Purkinje and Kaschkow, in the work of the latter, entitled, Meletemata
circa Mammalium dentium evolutionem. Not having been able, hitherto, to
procure Raschkow's work, I can only state from Burdach (Physiologic, French
ed. torn. iii. p. 498), that Purkinje's opinion appears to coincide with Mr.
Hunter's as to its being the organ which secretes that enamel. Mr. Hunter
has not described the processes which this body sends under the pulp, or the
PULPS AND SACS OF THE HUMAN TEETH. 21
branch divided into three twigs, one for each secondary base
of the pulp, and from all of these, radiating perpendicular
ramuscules proceeded, as in the case of a pulp with a pri-
mary base.
The arterial network, which was formed in the external
spongy membrane by the inosculation of these vessels with
those proceeding from the gums, transmitted small branches,
which ramified with such minuteness in the substance and
on the surface of that portion of the grey membrane to which
the granular matter adhered, that, when the latter was re-
moved, the former appeared to the naked eye a mass of
vermilion, but under a one-fourth of an inch lens exhibited a
network of the most minute injection. No injected vessel
could be seen in the granular substance.* The main dental
twig, after giving off all these branches, arrived at the base or
secondary bases of the pulp, and immediately divided into
many branches, which ramified in a contorted flattened
position, between the base or bases of the pulp and the mem-
brane of the sac. From these, smaller ramifications were
transmitted into the substance of the pulp, which ramified in
considerable numbers in the centre of its mass, but scarcely
at all near its surface or on its membrane, except in the neigh-
bourhood of, and at the point where, deposition of tooth-
space left between it and the base of the latter ; but his description is in other
respects so correct and characteristic, that it is difficult to account for the
manner in which the first part of his chapter on the formation of the enamel
has been so much misunderstood. Dr. Blake (p. 34) (although he described
the granular body as the inner membrane of the tooth-sacs, and as possessing
" no vessels capable of conveying red blood ") supposed that Mr. Hunter meant
by "another pulpy substance," the sacs of the permanent teeth. Mr. Bell
also in a note, vol. ii. Palmer's ed. Hunter's Works, p. 43, states that after
most accurate observations, he had come to the conclusion that the " pulpy
substance" mentioned by Hunter is nothing more than the inner membrane
of the sac turgid with blood and earthy matter preparatory to the secretion
of the enamel.
* Blake, Essay on the Structure and Fon/uUioti of the Teeth, p. 4.
22 ON THE ORIGIN AND DEVELOPMENT OF THE
substance had commenced, immediately beneath which the
vascularity was intense, both in the substance under, and on
the surface a little beyond, the edge of the scale.* This
surrounding vascularity had the appearance of a zone, and
was situated in the substance and on the surface of an ele-
vated portion of the pulp, which surrounded the scale of tooth-
substance.
The granular substance in contact with the tooth-substance
and its border had begun to be absorbed, and had consequently
become thinner in that situation than elsewhere, allowing the
subjacent vascularity to appear through it. No vessel could
be detected in the granular substance to account for the
absorption of its inner surface.
The ten little cavities had undergone no change, except
that the two or four anterior had become rather longer, and
were situated further from the surface of the groove, so as to
be placed rather behind than below the sacs. The anterior
cavity, in particular, although its walls were still in contact,
and required to be separated by the needles under water to
see its interior, had become pear-shaped. The fundus or
portion furthest from the gum exhibited on its floor a fold,
which lay in the direction of the edge of the future permanent
tooth, and near its apex there were two other minute folds,
one on the anterior wall, the other on the posterior. Beyond
this the cavity terminated in an opaque IMPERVIOUS line,
which soon disappeared. The substance of the gums had
become infiltrated with a quantity of gelatinous matter very
similar to the granular substance of the sacs. In consequence
of this infiltration the line of junction of the walls of the
dental groove had become obliterated, the substances of the
gums had become thicker, and the sacs more removed from
the surface.
The open portion of the groove (a, Fig. 19) had disappeared,
* Sevres, Easai sur I 'Anatomic d la Physiologic dcs Dents, p. 20.
PULPS AND SACS OF THE HUMAN TEETH.
23
Fig. 22.
but a longitudinal section showed that the lips only had
adhered, the walls had not. The follicle
(6, Fig. 22) had become a sac, in conse-
quence of which a cavity (&) remained be-
tween it and the surface of the gum. Gela-
tinous substance had been deposited in the
sac (6), and in the neighbourhood of the cavity below it
(b), as in the other sacs.
The lower jaw exhibited changes analogous to those in the
upper.
12. Child at Birth. A longitudinal section was made
through the posterior part of the
under jaw, when the sacs and pulps
of the posterior milk-molar, and of
the first permanent molar, and the
arrangements represented in Fig. 23,
were observed. (5) The sac and
Fig. 23. pulp of the posterior milk-molar ;
(6) the sac and pulp of the first permanent molar ; (&) the
cavity marked (b, Fig. 22).
The sac of the permanent tooth (6) was now almost wholly
imbedded in the base of the coronoid process of the jaw. The
cavity (b) which was attached to the upper part of the sac of
the permanent tooth by its posterior extremity, adhered by its
anterior extremity to that point of the gum which was attached
to the anterior edge of the base of the coronoid process, so
as to drag its surface at that point into a dimple. The cavity
(b) was consequently longer than it was at its first formation.
The granular substance had wholly disappeared. The
interior of the sacs had a villous highly-vascular appearance,
like a portion of injected intestinal mucous membrane. The
original opening of the sac (6) into the cavity (6) was indicated
on its inner surface by an indistinct circular lip. The sacs
24
ON THE ORIGIN AND DEVELOPMENT OF THE)
of one of the central incisives of the same fcetus exhibited
externally nothing peculiar. After a transverse section, it was
found to be composed of two, the temporary and permanent
combined.
The walls of the temporaiy sac (b, Fig. 23) were composed
of an external membrane, which was rather thick and con-
densed ; the inner could be separated from it, and had the
appearance, as in the molar sacs, of an injected villous
membrane. The little permanent sac was situated in the
substance of the outer membrane of the temporary sac, as if
the latter had been split to receive it. It was lined by a
membrane similar to that of the temporary, and exhibited
near the lower end of its posterior wall the incipient pulp,
which was evidently a development of the fold observed in
that situation at the fifth month. It terminated towards the
gum by an indistinct pointed extremity, from which a short
opaque impervious line proceeded, near to which the anterior
and posterior folds, observed at the fifth month, were seen.
13. The lower jaw of an infant about eight or nine months
old, in which the central incisives had cut the gum, was pre-
pared by removing a section from its external posterior lateral
aspect, so as to expose the sacs of the posterior milk-molar,
and of the anterior permanent
molar (x, Fig. 24). The latter (6),
instead of being buried in the base
of the coronoid process, was situated
further forward, and the cavity (ft)
having been displayed by a longi-
tudinal section of the former, was
found, comparatively speaking, to
have recovered its original small extent, being attached in-
feriorly to the top of the sac (6), and superiorly to the an-
terior edge of the base of the coronoid process.
PULPS AND SACS OF THE HUMAN TEETH. 25
Upon examining the two incisive teeth which had cut the
gum, it was found that a bristle could be inserted between
their surfaces and the gum for one-third of an inch. Through
the soft parts a transverse section was made, which was after-
wards continued through the jaw and one of the teeth by
means of a very fine saw.
It was now observed that the tooth (#, Fig. 24, y) had
acquired nearly two-thirds of its fang, and that the sac had
again become an open follicle (&). This follicle was shorter
than the whole length of the tooth by the length of the pro-
truding portion of the latter. At the mouth of the follicle, its
lining membrane was continuous with the surface of the gums,
and continued free till it arrived at the termination of the
enamel, where it united to the surface of the fang of the tooth,
but could be separated from it as a continuous membrane, and
at the lower end of the root it became continuous with the
surface of the pulp, whose base was yet considerable. Upon
removing the bone in front of the neighbouring lateral tooth,
which had not yet passed through the gum, it was observed
that the extremity of its fang, or rather the fundus of its sac,
was deeper in the jaw than that of the central by a length
equal to the protruding portion of the latter. This change of
level had not, however, taken place in the case of the alveoli,
that of the central being rather deeper than the lateral. The
space intervening between the bottom of the alveolus of the
central tooth and the fundus of its sac was occupied by a
spongy filamentous tissue, through which the dental vessels
and nerves proceeded.
14. The lower jaw of an infant, which had cut all its
milk-teeth, and which was probably between four and five
years old, was prepared in the same manner as the last.
The sac of the anterior permanent molar (6, Fig. 25) was
situated under the gum in front of the coronoid process, and a
26
ON THE ORIGIN AND DEVELOPMENT OF THE
new sac and pulp of a smaller size (7) had appeared buried in
the base of that process. The cavity
(b) was again lengthened out, being
attached anteriorly, at the anterior
edge of the base of the process, to
the gum, and posteriorly to the top
of the new sac (7). That portion of
the cavity formerly attached to the
sac (6) was now almost obliterated.
15. The posterior part of the .lower jaw of a child about
six years old was prepared by removing a section from its
internal posterior aspect, and making at the same time a
longitudinal section of the gum.
The sac (7, Fig. 26) had ad-
vanced from under the coronoid
process ; and another very small
sac and pulp had appeared en-
closed in a bony crypt under
the process, and communicat-
ing through the upper part of the bony cell of the sac (7)
with the gum, where it terminated in an opaque line or tail,
the last remains of the surface of adhesion of the dental groove.
SECTION II. A DESCRIPTION OF THE PULPS AND SACS FROM
THEIR FIRST APPEARANCE IN THE EMBRYO TILL THE
ERUPTION OF THE WISDOM-TEETH.
When we examine the upper jaw of a human embryo at
the sixth week, there is perceived between the lip and a semi-
circular lobe of a horse-shoe form (which is the primitive
condition of the palate) a deep narrow groove which ter-
minates on each side, behind the former, by curving inwards
on the soft mucous membrane. As this groove becomes
PULPS AND SACS OF THE HUMAN TEETH. 27
gradually wider, and the lip more lax in a direction from
behind forwards, there appears on its floor posteriorly, and
proceeding in the same direction, a ridge (the external alveolar
process) which speedily divides the original groove into two
others ; the outer one forming the duplicature of mucous
membrane from the inside of the lip to the outside of the
alveolar process, the inner one constituting what may be very
properly denominated the primitive dental groove, as the germs
of the teeth appear in it.
The inner side of the ridge already mentioned, after being
cut into three grooves whose concavities look inwards, and of
which the posterior is the deepest, terminates in a rounded
lobule, which is continuous with it anteriorly, while externally,
internally, and posteriorly, it is bounded by that portion of the
original groove which was situated behind the semicircular
lobe. The curves of the ridge are occupied by bulgings of
the semicircular lobe, so that the ridge and lobe, with their
curves and bulgings, are exactly similar to the arrangement
of the mucous membrane of the second compartment of the
stomach of the porpoise.
At some period between the sixth and seventh week a
longitudinal portion is cut off from the internal posterior edge
of the semicircular lobe, extending as far forwards as the
middle bulging, and about the same time the posterior bulging
becomes isolated and defined, under the appearance of an
ovoidal papilla, the long diameter of which is antero-posterior.
This papilla is the germ of the anterior superior milk-molar
tooth, the first tooth-germ which appears in the development
of the human body. It is at this period a simple free
granular papilla, like many others on the surface of the
mucous membrane and skin.
About the eighth week or second month a second papilla
appears at the point of projection of the ridge, between the
middle and anterior curve. This papilla, which is the germ of
28 ON THE ORIGIN AND DEVELOPMENT OF THE
the superior milk canine tooth, is rounded and granular, and is
bounded externally by a triangular lamina, which spreads out
into, and is continuous with, the inner edge of the ridge, having
its apex notched so as to fit the external aspect of the papilla.
During the ninth week the ridge advances in an indistinct
manner to the median line, and there appears on each side of
that line an oblong papilla with a notched lamina in front of
it, and immediately afterwards another smaller papilla and
lamina external to the former. These last papillae are the
germs of the incisive teeth, and are placed in connection with
the lateral elements of the intermaxillary system.
The primitive dental groove, which before the appearance
of the incisive germs terminated anteriorly at the outer ex-
tremity of the lateral intermaxillary lobules, now extends
forwards to the median line. The longitudinal lobule, and
the lobule opposite to it also, have lengthened out posteriorly,
and the intervening portion of the primitive groove has
become wider and not so curved. The sides of the groove
before and behind the anterior molar papilla have been
gradually approaching one another.
During the tenth week the incisive papillae make very
little advance, their anterior laminae only increasing some-
what in size. Processes from the sides of the primitive dental
groove, particularly the external one, approach and finally
meet before and behind the papilla of the anterior molar, so
as to inclose it in a follicle, through the mouth of which it
may be seen. A similar follicle is gradually formed round
the canine by the advancement inwards of its external notched
lamina, which at first appeared as a production of the ridge or
external lip of the groove. The germ of the posterior milk-
molar also appears as a small papilla towards the end of this
week behind the anterior molar, at the side and apparently as
a production from the rounded lobule, which terminates pos-
teriorly the outer ridge.
PULPS AND SACS OF THE HUMAN TEETH. 29
During the eleventh and twelfth week the incisives ad-
vance steadily. Septa pass between them from the outer to
the inner side of the groove, so that their papillae become
completely sunk in well-developed follicles. No material
change takes place in the anterior molar or canine ; but the
posterior molar papilla enlarges, and the terminal lobule of
the outer ridge folds gradually round it, so as to constitute its
follicle, behind which there still remains a portion of the
primitive groove.
The changes which ensue during the thirteenth week con-
sist in the completion of the follicle of the posterior molar,
and in the gradual change which takes place in the shape of
the different papillae. Instead of remaining, as hitherto, simple,
rounded, blunt masses of granular matter, each of them assumes
a particular shape. The incisives acquire in some degree the
appearance of the future teeth ; the canines become simple
cones ; and the molars become cones flattened transversely,
somewhat similar to carnivorous molars. During this period,
too, the papillse grow faster than the follicles, so that the for-
mer protrude from the mouth of the latter, while the depth of
the latter varies directly as the length of the fangs of their
future corresponding teeth, the canine follicle being deepest,
etc. etc. While the papillse are changing their shape, the
mouths of the follicles are undergoing a change which con-
sists in the development of their edges, so as to form operciila,
which correspond in some measure with the shape of the
crowns of the future teeth. There are two of these opercula
in the incisive follicles, one larger, anterior, and rather ex-
ternal, the second smaller, posterior, and internal. There are
three for the canines, an external and two internal, and four
or five for the molars, each corresponding with a tubercle ;
while their edges correspond with the grooves on the grinding
surfaces of these teeth.*
* It would be interesting to ascertain whether the opercula of the human
30 ON THE ORIGIN AND DEVELOPMENT OF THE
The inner lip of the dental groove (or the outer edge ol
the palate), which has been increasing for some time past, is
now, at the fourteenth week, so large as to meet and to apply
itself in a valvular manner to the outer lip or ridge, which
has also been increasing. The follicles at this time grow
faster than the papillae, so that the latter recede into the
former. The molar papillae gradually acquire two or three
additional small compressed tubercles on their sides, and their
apices become less conical, so that they still more resemble
the molar teeth of the carnivorous mammals.* The opercula
of the follicles continue to increase, so as almost to hide their
contained papillae.
The primitive dental groove, which at this period contains
ten papillae in as many follicles, and is situated on a higher
level than at first, may be now more properly denominated the
secondary dental groove. It is when in its secondary condition
that the groove affords a provision for the production of all
the permanent teeth, with the exception of the first or anterior
tooth-follicles may not be rudimentary organs, which are to attain their utmost
development in the sacs of the elephantoid, ruminant, and other compound
teeth, under the form of depending folds for the secretion of the intersecting
enamel and cement plates.
One may easily conceive the mode of formation of a composite tooth-sac,
by supposing the opercula, after their edges have met, to dip down back to
back between the divisions of the pulp, till they almost meet the common
body of the latter.
* This is another instance of the law of progressive development, by virtue
of which an organ, in the course of its formation, passes through phases which
correspond to permanent conditions of the same organ in other animals. A
human molar tooth-pulp is at first rounded, as in certain fishes ; then conical,
as in other fishes and reptiles ; then conical, but flattened transversely, gradu-
ally acquiring two or more additional conical tubercles, as in the carnivorous
mammals ; and finally, by the equalisation of the primary and secondary
tubercles, assuming the shape of the molars in the quadrumanous animals and
man. In the elephantoid, ruminant, and rodent animals, it probably under-
goes a further and ultimate change in the deepening of the rudimentary grooves
on the grinding surface.
PULPS AND SACS OF THE HUMAN TEETH. 31
molars. It is about the fourteenth or fifteenth week that we
begin to observe preparations made for this provision, -by the
gradual appearance of a little depression in the form of a
crescent, immediately behind the inner operculum of each of the
milk-tooth follicles. The concave edges of these depressions
are in contact with the attached margins of these opercula.
Those of the centre incisives appear first, then the laterals,
canines, anterior bicuspids, posterior bicuspids. About this
time the opercula close the mouths of the follicles, but with-
out adhering, the anterior closing first, then the laterals, and
so on in succession. The lips and walls of the secondary
groove now begin to cohere in a direction from behind for-
wards, the opercula and every part of the groove, with the
exception of the ten depressions for the permanent teeth, be*
coining rough, flocculent, and adherent. The follicles have
now become the sacs ; the papillae the pulps of the milk-teeth ;
and the crescent-formed depressions vacant cavities of reserve,
to furnish delicate mucous membrane for the future forma-
tion of the pulps and sacs of the ten anterior permanent teeth.
The general adhesion does not invade that portion of the
primitive dental groove which is situated behind the posterior
milk-molar follicle. This small portion retains its original
appearance, greyish-yellow colour, and smooth edges, for a
fortnight or three weeks longer, and affords a nidus for the
development of the papilla and follicle of the anterior per-
manent molar-tooth, the fundus of its follicle being situated
immediately behind the sac of the posterior milk-molar. The
cavities of reserve for the ten anterior permanent teeth are at this
period minute compressed sacs, with their sides in contact, and
situated between the surface of the gum and the milk-sacs.
The papillae of the milk-teeth, from the time that their
follicles close,* become gradually moulded into their peculiarly
* Herissant in the Mem. de I'Acadcmie Royale, 1754, p. 664, described
two grnns the " gencive permanent, " and the " gencive passagere. " His ideas
32 ON THE ORIGIN AND DEVELOPMENT OF THE
human shape. The molar pulps begin to be perforated also
by three canals, which, proceeding from the surface to their
centres, gradually divide their primary base into three second-
ary bases, which become developed into the fangs of the future
teeth. While this is going on, the sacs grow more rapidly
than the pulps, so that there speedily exists an intervening
space in which is deposited a gelatinous granular substance,
at first in small quantity, and adherent only to the proximal
surfaces of the sacs ; but ultimately, about the fifth month,
closely and intimately attached to the whole interior of these
organs, except for a small space of equal breadth, all round the
base of the pulp, which space retains the original grey colour
of the inner membrane of the follicle ; and as the primary base
of the pulp becomes perforated by the canals formerly men-
tioned, the granular matter sends processes into them, which,
adhering to the sac, reserve the narrow space described above
between themselves and the secondary bases. These processes
of granular matter do not meet across the canals, but dis-
appear near their point of junction. The granular matter is
closely applied, but does not adhere to the surface of the pulp.
" Whatever eminences or cavities the one has, the other has
the same, but reversed, so that they are moulded exactly to
each other."
Each branch of the dental artery, as it arrives at the fundus
of its destined sac, sends off a number of radiating twigs, which
run in the substance of the cellular submucous tissue (which
constitutes the outer membrane of the sac) towards the gum,
from which others proceed to inosculate with them. The
on the subject appear to have been derived from the examination of jaws in
which the lips and walls of the secondary dental groove "gencive passagere,"
had not become completely adherent or obliterated. In this way the indistinct
mouths of the milk-tooth sacs on the floor of the groove "gencive permanent,"
did not escape the notice of this most accurate observer. The cartilages of the
gum described by Serres (Essai, p. 10) are to be considered as the walls of the
groove in the semicartilaginous condition which they assume after closure.
PULPS AND SACS OF THE HUMAN TEETH. 33
combined twigs then ramify minutely in the true membrane
of the sac without sending the smallest twig into the granular
substance.* The dental branch, after giving off these saccular
twigs, divides into a number of contorted ramifications between
the base of the pulp and the sac, which from smaller ramusculi
are transmitted into the pulp itself. In the case of the molars,
the main branches divide into three secondary branches, one
for each of the secondary bases. From these, three sets of
saccular twigs, and three packets of contorted pulp-vessels,
take their origin.
While these changes have been taking place in the sacs of
the milk-teeth, the follicle of the first permanent molar closes,
and granular matter is deposited in its sac. The walls of that
portion of the secondary groove below it do not adhere ; the
edges alone do so. There is, therefore, a cavity of considerable
size below the sac of this tooth, or between it and the surface
* Mr. Fox (Natural History of the Human Teeth, p. 20) and Mr. Bell
(Anatomy of the Teeth, p. 54, and in a note, p. 39, vol. ii. Palmer's edition of
Hunter's Works) have both misunderstood the statements of Mr. Hunter and
Dr. Blake on the relative vascularity of the membranes of the tooth-sacs.
(Hunter's Natural History, p. 84, and Blake, p. 4.) What Blake denominates
the internal lamella is the enamel pulp of Hunter, Purkinje, and Easchkow,
the gelatinous granular substance described in the text. He, with great
accuracy states that it is "more tender and delicate, and seems to contain no
vessels capable of conveying red blood." Under the denomination "external
lamella " he includes the proper vascular mucous membrane of the sac, and the
external spongy submucous tissue. In his search after the germs of the per-
manent teeth, Blake's attention appears to have been directed to the tooth-sacs
when in the condition he describes. Mr. Hunter, again, who had a most
correct conception of the constitution of the sacs, has, with his usual sagacity,
not confounded the granular body, or, as he denominates it, "another pulpy
substance," with the proper membranes of the sacs. Accordingly, in his
account of the relative vascularity of the membranes of the sacs, he, when
describing the manner in which a tooth is formed, has taken no notice of the
pulpy substance. Dr. Blake describes the membranes of the sacs at an early
period ; Mr. Hunter, again, in a child at birth, at which time the external
membrane is not very vascular, and has assumed somewhat of the appearance
of a fibro-cartilage.
D
34 ON THE ORIGIN AND DEVELOPMENT OF THE
of the gum. This cavity is a reserve of delicate mucous mem-
brane to afford materials for the formation of the second per-
manent molar, and of the third permanent molar or wisdom-
tooth.
A little before this period tooth-substance begins to be de-
posited on the tubercles and apices of the pulps, which have
acquired round the point of deposition a raised border and a
zone-like vascularity ; and, synchronous with this deposition,
absorption takes place on the inner surface of the granular
matter immediately in contact with it. No vessel can be de-
tected running to the point of absorption, but ultimately the
granular matter becomes so thin as to allow the subjacent
vascularity to appear. The absorption goes on increasing as
the tooth-substance is deposited, and when the latter reaches
the base of the pulp the former disappears, and the interior of
the dental sac assumes the villous vascular appearance of a
mucous membrane. This change is nearly completed about
the seventh or eighth month.
Up to this period little change has taken place in the ten
anterior, or in the two posterior or great cavities of reserve.
The ten anterior have been gradually receding from the sur-
face of the gum, so as to be posterior, instead of inferior, to the
milk-sacs. The two or four anterior began about the fifth
month to dilate at their distal extremities, across which a fold
appears (which is the germ of the future pulp) lying in the
direction of the cutting edge of the future tooth ; and at the
proximal or acute extremities of the cavities two other folds,
an anterior and a posterior, appear.* These round off the un-
* These two folds are strictly analogous to the opercula of the milk-tooth
sacs. They never attain, however, the same high development as those of the
latter, remaining in a rudimentary state, apparently in consequence of the
almost saccular condition of the cavities of reserve. The existence of these
laminae in a rudimentary state proves that in the formation of the permanent
teeth there is a strict adherence to the law of follicular development even
when, in man at least, there is no apparent necessity for it.
*
PULPS AND SACS OF THE HUMAN TEETH. 35
defined apices of the cavities, and are strictly analogous to the
opercula of the milk-follicles.
The distal fold gradually acquires the appearance of a
tooth-pulp, while the proximal disappear by the obliteration
of the little undefined space beyond them.
The cavities of reserve have now become tooth-sacs, and
under this form they continue to recede from the surface of
the gum, imbedding themselves in the submucous cellular
tissue, which has all along constituted the external layer
of the milk-sacs, and in which the larger saccular vessels
ramify before arriving at the true mucous membranes of
the sacs. This implantation of the permanent in the
walls of the temporary tooth-sacs gives the former the
appearance of being produced by a GEMMIPAROUS process
from the latter.*
The dental groove was originally imbedded in an alveolar
groove. As the dental interfollicular septa are developed in
the former, osseous septa also begin to be formed in the latter.
These osseous septa are at first in the form of bridges, but
ultimately, at the sixth month, become complete partitions.
* It was this imbedding of the permanent in the walls of the temporary
tooth-sacs which deceived Dr. Blake, and led him to suppose that the former
derived their origin from the latter. Mr. Fox supported the same view of the
subject ; and Mr. Bell, in his own work (Anatomy, etc. etc. of the Teeth, p.
61), and more lately in his notes in Palmer's edition of Mr. Hunter's Works,
vol. ii. p. 37, has strongly urged the same doctrine. Mr. Bell has stated that
Mr. Hunter's "account of the manner in which the permanent teeth are formed
is exceedingly imperfect," but it is evident that if the account of the origin of
these teeth given in the text be correct, Mr. Hunter was not in error when he
supposed both sets to be of independent origin. Mr. Hunter was so correct a
thinker, that he did not account the circumstance of contiguity to be a proof
of dependence. He was apparently ignorant of the origin of both sets, and in
his usual cautious manner, when describing structure makes no observation on
the subject. The author of the Edinburgh Dissector holds the same opinion as
Mr. Hunter on this subject ; and in his excellent chapter on the teeth, although
he does not disprove the opinions of Dr. Blake and others, cautions the student
against supposing Mr. Hunter to be incorrect on this subject.
36 ON THE ORIGIN AND DEVELOPMENT OF THE
As the sacs increase in size, the alveoli increase also, and when
the permanent form slight projections behind the temporary
tooth-sacs, niches '''' are formed for them in the posterior walls
of the alveoli. Whilst this increase in the bulk of the sacs
and alveoli is going on, there is no proportionate increase in
the length of the jaw, in consequence of which, the sac of the
anterior permanent molar has been insinuating itself into, and
at the eighth month, or the full time, is almost wholly im-
bedded in, the maxillary tuberosity,t and has become situated
on a higher level than the milk-sacs, during which it has not
only drawn the surface of the gum upwards and backwards,
but has also lengthened out the great or posterior cavity of
reserve.
About this time the fangs of the milk-incisives begin to be
formed, in the accomplishment of which three contempora-
neous actions are employed viz. the lengthening of the pulp,
the deposition of tooth-substance upon it, and the adhesion to
the latter of that portion of the inner surface of the sac which
is opposite to it.
While the*fangs of the rnilk-teeth, particularly those in the
front of the jaw, are lengthening in the manner now described,
the pulps and sacs of the permanent teeth continue to increase,
and the bony crypts which contain them to enlarge in pro-
portion, the lower edges of the latter insinuating themselves
between the two former. As this process continues, the jaw
lengthens more rapidly, and when the infant is eight or nine
months old, there is so much room in the alveolar arch, that
the anterior permanent molar tooth begins to resume its
former position in the posterior part of the dental arch, and
the great cavity of reserve again to return to its original size
and situation.
About this time the central incisives begin to pass through
* Bell, Anatomy, etc. of the Teeth, p. 62.
f Hunter, Nat. Hist. Human Teeth, pp. 101, 102, 103.
PULPS AND SACS OF THE HUMAN TEETH. 37
the gum a process which is accomplished in the following
manner : The body of the tooth having been fully formed,
and coated with enamel, has also been acquiring a portion
of its fang by the triplex action formerly described ; in con-
sequence of which, a reaction takes place between the bottom
of the socket and the unfinished extremity of the fang.
This reaction causes the body of the tooth and the non-
adherent portion of the sac gradually to approach, and the
former finally to pass through the surface of the gum. Till
the time that the edge of the tooth passes through the gum,
the fundus of the sac, and consequently the base of the pulp
with the extremity of the fang, never change their common
relative position in the jaw. At the moment, however, that
the tooth passes through the gum (when the non-adherent
portion of the sac resumes its primitive follicular condition,
its inner membrane becoming continuous with the mucous
membrane of the mouth) the non-adherent portion of the sac
shortens more rapidly than the fang lengthens, in consequence
of which the adherent portion with the fang itself separates
from the fundus of the alveolus and the body of the tooth
advances through the gum.* A space is thus left between the
top of the alveolus and the fundus of the sac, occupied by
cellular tissue, and traversed by the vessels and nerves. The
alveolar cavity at the same time rapidly adapts itself to the
new condition of its contents, advancing its edges so as to
clasp the root, which has during these rapid changes been
steadily lengthening a process which now goes on with
greater rapidity, as it is conducted in a comparatively empty
* The movement of the unfinished extremity of an incisive tooth from the
fundus of its alveolus will explain what I have commonly remarked, and what
must have been observed by medical practitioners, that from the time that the
edge of the tooth appears through the gum, it advances more rapidly than can
well be accounted for by the usual rate of lengthening of its fang. This ad-
vance is not invariably rapid, but may be observed in all the incisive teeth, if
careful daily examination be made during a normal dentition.
ON THE ORIGIN AND DEVELOPMENT OF THE
space. The pulp continues to lengthen till its base is no
larger than the fasciculus of vessels and nerve which enters it.
The orifice of the cavity of the tooth also diminishes to the
same size, and through it the surface of the pulp becomes
continuous with the adherent portion of the sac and con-
sequently with the mucous membrane of the mouth. The
adherent portion of the sac has now attained its maximum,
and the free or open portion its minimum size, having been
reduced to that narrow portion of the gum which forms a
vascular border and groove round the neck of the perfected
tooth*
During the period that the milk-teeth have been advanc-
ing along with their sockets to their perfect state and ultimate
position in the jaw, the permanent sacs have been receding in
an opposite direction, and have, as well as their bony crypts,
been enlarging, the edges of the latter, insinuating themselves
so far between the former and the milk-sacs, that at last they
are only connected by their proximal extremities, and ulti-
mately, when the lower edges of the crypts sink so far as to
have become the posterior lips of the alveoli of the milk-teeth,
the notches of communication between the latter and the
permanent alveoli are forced, under the form of foramina,
into a position on the anterior surface of the palate, one
behind each milk-alveolus. The sacs of the bicuspids having
assumed a position directly above the milk-molars, the hole
* This vascular "border may be seen in healthy gums which have not been
disturbed by the deposition of tartar, and is beautifully displayed in two wet
injected preparations in the Bell collection, Museum of the Royal College of
Surgeons, Edinburgh (Bell, C. iii. Nos. 25 and 56).
It is interesting to observe that one of the first physiological effects of mer-
cury viz. excitation of the gastro -intestinal compound glands and simple
mucous follicles is also displayed in a similar manner in the borders which
surround the necks of the teeth, which are the remains of the free portions of
the tooth-sacs, while it at the same time acts upon the adherent portions and
their submucous tissue, raising the teeth from their sockets, and affecting the
jaw from contiguity.
PULPS AND SA.CS OF THE HUMAN TEETH. 39
of communication is never removed from the sockets of the
latter.
The cords of communication which pass through these
foramina are not tubular, although in some instances a portion
of the unobliterated extrafollicular compartment of the ori-
ginal little cavity of reserve may be detected in them. They
are merely those portions of the gum which originally contained
the lines of adhesion of the depressions for the permanent
teeth in the secondary dental groove, and which have been
subsequently lengthened out, in consequence of the necessarily
retired position in which the permanent teeth have been
developed during the active service of the temporary set.
The cords and foramina are not obliterated in the child,
either because the former are to become useful as " guber-
nacula," and the latter as " itinera dentium," or much more
probably, in virtue of a law, which appears to be a general
one in the development of animal bodies viz. that parts
or organs which have once acted an important part, however
atrophied they may afterwards "become, yet never altogether
disappear so long as they do not interfere with other parts or
functions. t
The sacs of the permanent teeth derive their first vessels
from the gums ; ultimately they receive their proper dental
vessels from the milk-sacs, and as they separate from the
latter into their own cells, the newly-acquired vessels con-
joining into common trunks, retire also into permanent dental
canals.
It was stated above that, in the child at the seventh or
eighth month, when the central incisives were passing through
the gums, the jaw had lengthened so much as to allow the
first permanent molar to retire from the maxillary tuberosity,
and to resume in some measure its position downwards and
forwards in the same line with the other teeth, and also to
reduce the great cavity of reserve to its primitive size. This
40 ON THE ORIGIN AND DEVELOPMENT OF THE
cavity of reserve now begins to lengthen, to bulge out, and to
curve backwards and upwards at its posterior extremity, under
the form of a sac, into the mass of the maxillary tuberosity ;
a papilla or pulp appears in its fundus, and a process of con-
traction separates it from the remainder of the cavity of
reserve, which still adheres to its proximal wall by one
extremity, while by the other it is continued into the
substance of the gum under the anterior molar. This new
sac, which is that of the second permanent molar, now
occupies the position in the maxillary tuberosity which
the first permanent did before it. It afterwards leaves this
retired position, in consequence of the lengthening of the
jaw allowing it to fall downwards and forwards into the
line, and on a level with the other teeth.* Before it leaves
the tuberosity altogether, the posterior extremity of the
remainder of the cavity of reserve sends backwards and
upwards its last offset the sac and pulp of the wisdom-
tooth, which speedily occupies the tuberosity after the
second molar has left it, and ultimately, when the jaw again
lengthens for the last time, at the age of nineteen or twenty,
takes its place at the posterior extremity of the range of the
adult teeth.
The wisdom-teeth are the second products of the posterior
* The curved lines which the posterior cavities of reserve, and the sacs of
the molar teeth, describe in their progress to and from the maxillary tuber-
osity, and the coronoid process, and the peculiar position in which the pulps
are consequently developed, explain satisfactorily certain normal and abnormal
conditions of these teeth : 1. The curves which the combined grinding sur-
faces of the molar teeth present, convex downwards and backwards in the
upper jaw, concave upwards and forwards in the lower. 2. The peculiar
manner in which the fangs of the molars, particularly the inferior, are bent
backwards. 3. The occasional horizontal position of the wisdom-teeth, the
crowns of the inferior being directed forwards, those of the superior backwards.
This abnormal position is the cause of much annoyance and danger to the
patient, and of difficulty to the surgeon.
PULPS AND SACS OF THE HUMAN TEETH. 41
or great cavities of reserve, and the final effects of develop-
ment in the secondary dental groove.*
In the lower jaw, as in the upper, dentition commences in
a deep narrow groove, situated between the lip and a semi-
circular lobe. This groove, instead of terminating in a simple
curve posteriorly, as in the upper jaw, becomes shallow, and
assumes a sigmoidal form upon the surface of the posterior
bulbous ovoidal portion of the lobe.
About the seventh week the lip becomes very loose, and
separates widely from the lobe, between which and the former
a ridge appears, growing from behind forwards, and dividing
the original groove into two, an outer one the labial dupli-
cature of mucous membrane, and an inner the primitive
dental groove. This ridge, which, as in the upper, does not yet
extend to the incisive portion of the jaw, is flat, or in the
same continuous plane with the bottom of the dental groove,
and its lip is turned out, or overhangs the labial mucous
membrane. The inner lip of the groove is formed by the
semicircular lobe, which has become thin, and arched over
the groove, particularly anteriorly, where it is cut into four
festoons, two on each side of the median line ; and posteriorly,
where it still retains the appearance of an oval lobe, from
under which the outer lip or ridge appears to proceed. The
groove curves inwards between the two lips posteriorly, under
a form which is evidently a development of the original
sigmoidal groove.
Near the posterior extremity of the groove there is an
elevation of a small portion of its floor, which speedily
becomes the germ or papilla of the inferior anterior milk-
molar tooth the second tooth which appears in the primitive
* It is probable that the successive dentitions of the elephant are conducted
in a cavity of reserve, which must consequently exist even in the adult animal,
till a late period of its life. If such be the case, the molar dentition of the ele-
phant, and the formation of the human adult molars, are analogous processes.
42 ON THE ORIGIN AND DEVELOPMENT OF THE
development of the human body. During the eighth week
the elevation already mentioned becomes a papilla, length-
ened from behind forwards, and flattened transversely. About
the same time another papilla, bounded by a notched lamina,
similar to those on the upper jaw, makes its appearance
further forward in the groove. This papilla is the germ of
the inferior milk-canine. The dental groove is about the
same time continued forward to the median line, not by the
advancement of its outer ridge, but by the elevation of its
floor. Its posterior portion also has become wider and not so
curved.
During the succeeding week the incisives make their
appearance, the centrals first.
From this time all the eight papillae continue to increase.
The notched laminae shoot inwards to the inner lip of the
groove, near which they meet and join slight projections from
it. About the eleventh or twelfth week the germ of the
posterior milk-molar appears in the curved portion of the
groove, and is developed in the usual manner.
Crescent-like depressions appear in the secondary groove,
on the inner side of the mouths of the milk-follicles, as in the
upper jaw.
The secondary groove adheres, leaving a posterior open
portion, in which are developed the papilla and follicle of the
first permanent molar. This follicle closes, as well as the lips
of the portion of groove above it. There are now in the jaw
ten milk-tooth sacs, two permanent-tooth sacs, ten anterior
cavities of reserve, and two great or posterior cavities of
reserve ;* the ten anterior for the development of the incisives,
* The mucous membrane constituting the cavities of reserve exists in a
condition which has hitherto been considered by anatomists as peculiar to the
serous membranes. A dental cavity of reserve is a shut sac, lined by a true
mucous membrane, which is isolated from the general mucous system, and per-
forms no special function, till it is called upon to supply what it alone can
afford, materials for the development of a tooth.
PULPS AND SACS OF THE HUMAN TEETH. 43
canines, and bicuspids ; the two posterior for that of the second
and third molar,* the coronoid process acting the part which
the maxillary tuberosity did in the upper jaw.
SECTION III.
1. On the Division of Dentition into Stages. As dentition
is a process, not only very complicated in its details, but of
very lengthened duration, extending over nearly eight months
of intra-uterine, and above twenty years of extra-uterine
existence, the understanding and further investigation of it
may be facilitated by dividing it into stages. The most
natural division, one which is not artificial, but clearly indi-
cated by the phenomena themselves, is into three stages,
according to the position of the pulp in relation to its con-
taining cavity 1st, follicular stage ; 2d, saccular ; 3d, eruptive.
We ought probably to consider, as anterior to the follicular,
the papillary stage t during which the follicle or sac does not
exist, and the future pulp is a simple papilla on the free surface
of the gastro-intestinal mucous membrane. As this stage,
* The cavities of reserve are occasionally somewhat undefined, two or three
being conjoined, particularly posteriorly. Sooner or later, however, they
become distinct. The great cavity frequently stretches forwards over the sacs
of the milk-molars.
f Most anatomists have supposed the germs of the teeth to appear as shut
sacs, full of a fluid, the pulps being formed by inspissation of the latter, or by
development from the walls of the former. Neither Mr. Hunter nor Mr. Bell
has stated anything very definite on this subject. The pulp must be con-
sidered as the principal part of the organ, and as the element which appears
first. The sac is a mere subsidiary part, supplied for purposes of development
and nourishment. Handbuch der Anatomic des Menschen, von. H. Hilde-
brandt, besorgt. von E. H. Weber, Erster Band, p. 212 ; Handbuch der
Entwickelungs-geschichte des Menschen, von Yalentin, p. 482 ; Arnold, Salz-
burg Medicinisch-Chirurgisch Zeitung, 1831, Erster Band, p. 236 ; Cruveilhier,
Anatomie Descriptive, vol. i. p. 518 ; Serres, Essai sur V Anatomie, etc., des
Dents, p. 59; Ph. Fr. Blandin, Anatomie du Systeme Dentaire, etc., p. 87;
Blake, Essay on the Human Teeth, p. 2.
44 ON THE ORIGIN AND DEVELOPMENT OF THE
however, is short in its duration, and simple in its details, it
may be included in the first stage.
The first or follicular stage comprehends all the phenomena
which present themselves from the first appearance of the
dental groove and papillas till the latter become completely
hid by the closure of the mouths of their follicles, and of the
groove itself. It is upon this hitherto unknown stage of
dentition that I have insisted so much in the former sections
of this paper.
The second or saccular stage is the one with which ana-
tomists have been so long familiar, during which the papillae
are pulps, and the open follicles which contain them are shut
sacs, when the tooth-substance and the enamel, constituting
the teeth themselves, are deposited. It is during this stage,
also, that some of the most interesting phenomena in the
formation of the alveolar processes present themselves.
The third or eruptive stage includes the completion of the
teeth, the eruption and shedding of the temporary set, the
eruption of the permanent, and the necessary changes in the
alveolar processes.
When viewed in reference to an individual tooth, these
three stages are distinct ; but when viewed in reference to
both sets, and to the whole process of dentition, they become
somewhat intermingled.
When considered in the latter point of view, we may state
that the follicular stage commences at the sixth or seventh
week, and terminates at the fourth or fifth month of intra-
uterine existence ; that the saccular commences at the ter-
mination of the first, and lasts for certain of the teeth till the
sixth or eighth month, and for others till the twentieth or
twenty-fifth year of extra-uterine existence; and that the third
or eruptive commences at the sixth or eighth month, and lasts
till the twentieth or twenty-fifth year.
PULPS AND SACS OF THE HUMAN TEETH. 45
On the Anterior Permanent Molar Teeth. The anterior
permanent molar is the most remarkable tooth in man, as it
forms a transition between the milk and permanent set. If
considered anatomically, it is decidedly a milk-tooth ; if
physiologically, a permanent one. In a former part of this
paper, it was stated that the papilla and follicle of this tooth
were developed in a small portion of the primitive dental
groove, which remained open for that purpose till the fourth
or fifth month, while all the other permanent teeth were pro-
ductions, not from the primitive groove, but from small
non-adherent portions of the secondary groove, which lay in
a level superior to the shut orifices of the sacs of all the milk-
teeth, and of the tooth in question the first permanent molar.
In reference to its function, however, as the most efficient
grinder in the adult mouth, we must consider it as a permanent
tooth. It is a curious circumstance, and one which will readily
suggest itself to the surgeon, that, laying out of view the
wisdom-teeth, which sometimes decay at an early period from
other causes,* the anterior molars are the permanent teeth,
which most frequently give way first, and in the most sym-
metrical manner, and at the same time, and frequently before
the milk set.
On the Tardy Development of the Superior Incisive Teeth.
A reference to the first section of this paper will show that at
the ninth week, when the {mpillse of the superior incisives are
quite distinct, those of the inferior are with difficulty recog-
nised. This is a fact which may be included under a law
which will be more fully referred to afterwards viz. that the
dentition of the upper precedes, and is always in advance of,
the same process in the lower 'jaw. A week or two later,
however, when the papilla? of the inferior incisives are
imbedded and hid in deep follicles, those of the superior are
* Bell, Anat. etc. of the Teeth, p. 133.
46 ON THE ORIGIN AND DEVELOPMENT OF THE
nearly in their original condition. Although the latter recover
in some degree their lost ground, yet, as every one knows, the
inferior central incisive almost always cuts the gum before the
superior, and the lateral sometimes does so also. In order to
explain this apparent exception to the law above mentioned,
it will be necessary to go a little into the history of the inter-
maxillary bones, in doing which reference must necessarily be
made to some of the other bones of the face and head.
When the superior portion of the large common nasal
buccal and pharyngeal cavity is exposed in an embryo of the
sixth or seventh week, by removing the lower jaw, we observe
the boundary of the future palate to be defined by what has
been denominated in a former section the horse-shoe lobe (c,
Fig. 2). Attached to the posterior inner edges of this lobe
two other lobes are seen. These grow from behind forwards,
and from without inwards, and complete the palate by joining
in the median line, being assisted in doing so posteriorly by
two other smaller lobes behind the posterior extremities of
the horse-shoe lobe. In the two first lobes become developed
the palatine plates of the superior maxillary bones, and in the
two smaller posterior the palatine plates of the palate bones.
The bar (h, Tigs. 2 and 4), which ultimately coalesces
below with the median line of suture of the four last men-
tioned lobes, is proved by development to contain the nucleus
of the vomer.
The median lobule (m) and its' two lateral and anterior
appendages (n ri) form the anterior division of the embryonal
palate. Of these three, the two lateral are observed in the
course of development to contain the nuclei of what are
usually denominated the intermaxillary bones. With regard
to the median it may be stated that, as all the other lobules
which appear in the soft pulpy texture of the foetal palate
are proved by development to contain the nuclei of all the
well-known bones of this region, I am inclined to consider it
PULPS AND SACS OF THE HUMAN TEETH. 47
as indicative of the existence of the rudiment of a bone also,
especially when the interesting antagonism, which I will show
exists between it and the lateral lobules, is taken into con-
sideration.*
As the object of this part of my paper, however, is not to
discuss the osteogenesis of the human head, but to explain
why the inferior incisive teeth, although later in their appear-
ance, are yet more rapid in their progress than the superior,
I shall now recall some circumstances formerly detailed re-
garding the development of the three intermaxillary lobules,
immediately before and for some time after the appearance of
the incisive papillae.
During the seventh week the three lobules are equal, and
there is no appearance of either the upper or lower incisive
teeth.
During the eighth week the median lobule has increased
relatively, and the laterals only absolutely ; while as yet
there is no appearance of either the upper or lower incisives.
During the ninth week the median has diminished re-
latively, and in the transverse direction ; the laterals again
have increased relatively and also in the transverse direction.
This relative transverse increase of the lateral lobules is syn-
chronous with the first appearance of the upper incisives. The
inferior incisives are so indistinct at this time, as to be recog-
nised with difficulty as slight bulgings on the floor of the
dental groove.
During the next fortnight the relative size of the median
* A small cartilaginous body exists in the median intermaxillary lobule of
the child at birth. It is situated in front of the inferior orifice of the naso-
palatine canal, and between the mucous membrane and periosteum.
The median intermaxillary lobule exists in the adult palate, and may be
felt behind and between the central incisives. Median intermaxillary bones
and cartilages exist in certain of the lower vertebrata.
The bar-like vomer of the human embryo at the sixth and seventh week
reminds the anatomist of the adult vomer of the lower vertebrata.
48 ON THE ORIGIN AND DEVELOPMENT OF THE
and lateral lobules remains the same, and there is no further
development of the superior incisives. During the same
period the inferior incisives have been rapidly increasing.
Afterwards the median undergoes much relative trans-
verse diminution, while at the same time the laterals acquire
a remarkable relative increase, which is accompanied by a
corresponding development of the superior incisives ; but the
inferiors have now got so much in advance as to retain their
advantage ever after.
On the Laws which regulate the development of the Pulps
and Sacs, and the period of appearance of each of the Tooth-
Germs. In the description which has been given of the earlier
phenomena of dentition, it will be perceived that many of
them range themselves under the laws recognised by MM. G.
St. Hilaire, and Serres viz. the law of symmetry (loi de sym-
metric), the law of conjunction (loi de conjugaison), the law
of balancing or antagonism (le balancement des organes), and
the law of eccentric development (loi du developpement
excentrique).
The primitive and secondary dental grooves, the follicles,
the cavities of reserve, the osseous alveoli of the milk-teeth
and their septa, are all formed originally of two halves, which
ultimately join according to the laws of symmetry and con-
junction.
The pulps of the milk-teeth* with their notched laminae
are productions from the external lip or ridge of the groove.
The interfollicular septa, and the osseous alveolar septa, are
also developed from without inward (loi du developpement
excentrique).
I have already pointed out the beautiful example of
* It is a curious fact, that the first tooth-germs which appear viz. those
of the superior anterior and inferior anterior milk-molars are not productions
from the external lip of the dental groove, but bulgings on its floor.
PULPS AND SACS OF THE HUMAN TEETH. 49
antagonism which exists between the median and lateral
elements of the intermaxillary system ; and I may now point
out, from among the facts formerly detailed, a few instances
of the same kind, which must be referred to the same general
expression (loi de balancement).
1. Before the tenth week the upper lip is full and pro-
minent, but at that time it begins to recede and gradually to
disappear anteriorly, so as to expose the follicles and papillae
of the incisive teeth. It afterwards begins to regain its former
position and size, and at the fourteenth or fifteenth week it is
as large as the inferior, which from the first has not changed
its appearance.
At the tenth week, when the lip begins to recede, the
maxillary palate advances its anterior extremity, so as to con-
ceal in some degree the intermaxillary palate (median and
lateral lobules). When the middle of the lip has disappeared,
the maxillary has not only encroached upon the intermaxil-
lary, but has also thrown itself into a bundle of irregular folds
at its anterior part. As the maxillary palate retires, and the
folds become regular crenated rugse, the anterior part of the
lip again appears, and at the fifteenth or sixteenth week, it is
full and prominent, when the maxillary palate has retired to
its proper position.
2. When the outer lip of the primitive dental groove
sends off the laminge, which constitute the greater part of each
of the interfollicular septa, and the floor of the secondary
groove, the lip itself almost disappears.
The inner lip, again, which contributes a very small share
towards the accomplishment of this process, becomes so much
enlarged as to cover the whole groove.
3. The external and internal lips of the primitive dental
groove are, originally, equally prominent. The former, when
it sends off the interfollicular septa, diminishes, while the latter
increases. When all the follicles of the primitive groove have
E
50 ON THE ORIGIN AND DEVELOPMENT OF THE
been completed, the external lip begins to increase, and the
internal to diminish. This increase of the external lip goes
on after the closure of the secondary groove, until, at the fifth
month, it becomes very prominent, and is divided into an in-
cisive, a canine, and molar portion, each of which has a general
similarity in shape to the acting portions of the correspond-
ing divisions of the future tooth-ranges. As long as it remains
in this condition it is employed by the infant as a masti-
cating organ. During this period the internal lip has alto-
gether disappeared, except a small portion posteriorly ; but a
short time before the milk-teeth appear, it again increases, and
the raphe of the dental groove, instead of being hid behind the
base of the external lip, is situated on the ridge of the dental
arch, which now, as at first, is composed of two equally-deve-
loped portions. The raphe forms a little border in the
situation just mentioned, and is familiar to the eye of the
surgeon, who, by its disappearance at any particular point,
can satisfy himself of the proximity of the milk-tooth under it.
Careful observation of the whole process of Dentition in man
leads to the following conclusions:
Milk Teeth. 1. The milk-teeth are formed on both sides of
either jaw, in three divisions, a molar, a canine, and an incisive,
in each of which dentition proceeds in an independent manner.
2. The dentition of the whole arch proceeds from behind
forwards the molar division commencing before the canine,
and the latter before the incisive.
3. The dentition of each of the divisions proceeds in a
contrary direction, the anterior molar appearing before the
posterior, the central incisive before the lateral.
4. Two of the subordinate phenomena of dentition also
obey this inverse law, the follicles closing by commencing at
the median line, and proceeding backwards, and the dental
groove disappearing in the same direction.
PULPS AND SACS OF THE HUMAN TEETH. 51
5. Dentition commences in the upper jaw, and continues
in advance during the most important period of its progress.
The first tooth-germ which appears is that of the superior
anterior molar, which precedes that of the inferior anterior
molar.
The apparent exception to this law in the case of the in-
ferior incisive has already been explained.
Permanent Teeth. 6. The germs of the permanent teeth,
with the exception of that of the anterior molar, appear in a
direction from the median line backwards.
7. The milk-teeth originate, or are developed, from the
mucous membrane.
8. The permanent teeth, also originating from mucous
membrane, are of independent origin, and have no connection
with the milk-teeth.
9. A tooth-pulp and its sac must be referred to the same
class of organs as the combined papilla and follicle from which
a hair or feather is developed viz. bulbs.*
* An abstract of this paper was read at the last meeting of the British
Association for the Advancement of Science.
Dr. Allen Thomson stated to me at that time, that he had no doubt that
the fact of the milk-tooth sacs being at one period open follicles had been ob-
served, but that, then, he could not inform me where I could find it mentioned.
I saw Dr. Thomson in Edinburgh a few weeks afterwards, when, on looking
into Valentin's work on Development (ffandbuch der EntwicJcelungs-ge-
schichte des Menschen), he pointed out to me the fact that Arnold had observed
that the milk-tooth sacs were formed by a duplicature of the mucous mem-
brane of the mouth, and had inserted a notice of the discovery in the Salzburg
Med. Chir. Zeitung, 1831, p. 236. In order that Professor Arnold's discovery
(which appears to have been altogether overlooked both in this country and in
France) may be more generally known, I will give all his facts as he has re-
corded them. His notice occupies less than a page, and I am not aware that
he has extended it elsewhere. At p. 236, loc. cit. he has observed, "In an
embryo at the ninth week, we may perceive in both jaws, on the projecting
edges of the gums, a proportionally pretty deep furrow, with ten depressions
in it ; a little later we may see a flat surface, on which there are many open-
52 PULPS AND SACS OF THE HUMAN TEETH.
ings, communicating with small sacs, into which fine bristles may be passed.
At the third month the sacs of the second molars may be seen communicating
with the cavity of the mouth by small holes. The openings of the remaining
sacs are soon closed by the mucous membrane of the mouth.
"The sacs of the permanent teeth are also formed immediately from the
mucous membrane of the mouth, partly at the fourth month of foetal exist-
ence, partly towards the end of that period, partly at birth. Once only, in a
new-born child, I observed behind the most prominent edge of the gums
several openings which led to the sacs of the incisives and canines, and which
are usually already obliterated before birth."
These are all the facts Arnold has recorded, and from them it appears that
he was acquainted at that time with the secondary dental groove, the ten milk-
follicles, and the ultimate closure of the latter. So far as we can judge from
his brief notice, he appears to have been unacquainted with the mode of for-
mation of the permanent follicles, supposing them to be formed immediately
(unmittelbar) from the mucous membrane of the mouth, an opinion which is
very prevalent among the continental anatomists. I can only account for the
openings he mentions in the new-born child by arrest of development, or by
supposing that he had observed a few of the Tartar glands of Serres (Glandes
dentaires, Essai, etc., p. 28), which are best seen at the period to which he
alludes.
Having now mentioned all the facts which Professor Arnold has published,
I may be allowed to state that I had made out all the facts detailed in this
paper before I was aware that any of them had been on record ; that I had
given an account of them at the last meeting of the British Association, before
I knew of Professor Arnold's notice ; and that this paper was in the hands of
the Editor of the Edinburgh Med. and Surg. Journal before I had an oppor-
tunity of seeing the Salzburg periodical.
I had also demonstrated the principal facts in the follicular stage of denti-
tion, in 1835, to Mr. Nasmyth, to whom I am deeply indebted for the infor-
mation he has given me respecting the anatomy and surgery of these organs,
and in whose cabinet I at that time deposited preparations illustrative of the
facts.
FOLLICULAR STAGE OF DENTITION IN THE RUMINANTS. 53
II. ON THE FOLLICULAE STAGE OF DENTITION
IN THE EUMINANTS, WITH SOME EEMAKKS
ON THAT PEOCESS IN THE OTHEE OEDEES
OF MAMMALIA.
SINCE the meeting of the British Association in 1838, at which
the paper on the development of the human teeth was read,
I have detected the follicular stage of dentition in the pig,
rabbit, cow, and sheep, but have not had an opportunity
of examining it in those animals in which observations
would have been most valuable. I have been able to
verify, what was at that time stated as probable viz. that
all the permanent teeth, with the exception of the first molar,
which does not succeed a milk-tooth, are developed from the
internal surface of cavities of reserve, and that the depending
folds of the sacs of composite teeth are formed by the lips of
the follicles advancing inwards after closure of the latter. In
tracing the progress of development of the pulps and sacs
of the teeth in the cow and sheep, from their first appear-
ance, as minute as possible, on the full surface of the
membrane of the mouth, or on the internal surface of the
cavities of reserve, till they have acquired their ultimate
configuration, I have to announce the fact, that at an
early period of the embryonic life of these animals they
possess the germs of canine and superior incisive teeth ;
the former existing as developed organs in two or three
genera only of ruminants, the latter being found in the
aberrant family of camels. These germs present them-
selves under the form of slight dimples in the primitive
groove, and after the closure of the latter, they remain
54 ON THE FOLLICULAK STAGE OF
for a short time as opaque nodules imbedded in the gum,
in the course of the line of adhesion. The existence of
germs of canines and superior incisors in the cow and sheep
is highly interesting, as it shows how general the law of unity
of type is within certain limits. Geoffrey St. Hilaire was the
first to announce the existence of tooth-germs in the foetus of
the Balcena mysticetus, a fact which has been verified by Dr.
and Mr. Frederic Knox, in whose museum there is a prepara-
tion exhibiting the germs under the form of sacs and pulps.
Although the germs never arrive at this stage of perfection in
the cow and sheep, they are yet distinct enough to indicate
their existence ; and I have no doubt that when embryos of
other partially or wholly edentulous mammals have been exa-
mined, similar results will be obtained. The peculiar manner
in which the sac of a ruminant molar, and probably of every
other composite tooth, is formed, may be best seen in longi-
tudinal or transverse sections of the sac and pulp of the fourth
permanent molar of the sheep or cow. The internal surface
of the cavity of reserve is seen to end in a fold or folds ; when
these meet, they begin to curve towards the papilla, and to
enter parallel to one another the cavity or notch which
is simultaneously forming in the latter. As soon as the
edges of the folds meet, the granular matter denominated
enamel-pulp by Hunter (the formation of which was de-
scribed in the human embryo, at the last meeting of the
Association) begins to be deposited, cementing together the
opposing folds, sealing up the new sac, separating it from the
rest of the cavity of reserve, filling up the space existing
between the pulp and sac, and ultimately assisting in the
formation of the depending folds of the latter.
A distinction must be drawn between those permanent
teeth which are developed from the primitive, and those
which are developed from the secondary groove. I have been
in the habit of dividing the teeth of these animals, the denti-
DENTITION IN THE RUMINANTS. 55
tion of which I have examined, into three classes viz. ~Lst.
Milk or primitive teeth, developed in a primitive groove,
and deciduous. 2d. Transition teeth, developed in a primi-
tive groove, but permanent. 3d. Secondary teeth, developed
in a secondary groove, and permanent. I hope that other
anatomists may verify and extend this line of research, as
the results appear to me not only confirmatory of certain
great general laws of organisation, but as leading, by the
only legitimate path, to the determination of the organic
system to which the teeth belong (a subject exciting great
interest at present), and as it may enable us in investigating
the relations of dental tissue to true bone, to avoid the error
of confounding, what there appears to be a tendency to do,
analogy with affinity. In recapitulation of the principal
facts it may be said : 1. In all the mammalia examined
the follicular stage of dentition was observed. 2. The pulps
and sacs of all the permanent teeth of the cow and sheep,
with the exception of the fourth molar, are formed from
the minor surfaces of cavities of reserve. 3. The depend-
ing folds of the sacs of composite teeth are formed by the
folding in of the edges of the follicle towards the base of
the contained pulp, the granular body assisting in the for-
mation of these folds. 4 The cow and sheep (and probably
all the other ruminants) possess the germs of canines and
superior incisives at an early period of their embryonic
existence.
56 ON THE MODE IN WHICH MUSKET-BULLETS BECOME
III. ON THE MODE IN WHICH MUSKET-BULLETS
AND OTHEE FOKEIGN BODIES BECOME IN-
CLOSED IN THE IVOKY OF THE TUSKS OF
THE ELEPHANT. PLATE II.
MUSKET-BULLETS are occasionally found inclosed in ivory,
and every anatomical museum contains specimens of this
kind. Why bullets should be so frequently met with in this
situation it is not easy to say : the head of the elephant
appears to be generally aimed at, and foreign bodies, when they
enter the tusks, instead of being removed in the usual manner
are retained by the process, an investigation of which is to
form the subject of the present paper. My attention was
directed to this subject by Mr. Syme, who submitted to me
for examination some highly interesting specimens of bullets
in ivory, presented to the Anatomical Museum of the Uni-
versity by Sir John Eobison. Sir John has also kindly
afforded me an opportunity of examining some remarkable
examples of wounded ivory, and Sir George Ballingall has
directed my attention to preparations in his possession, which
have satisfied me of the truth of those opinions on the sub-
ject which I shall now have the honour of submitting to the
Royal Society.
One circumstance was at once detected in all these speci-
mens, and its importance was evident, as affording a clue to
the explanation of the mode of inclosure. The circumstance
to which I allude is, that in none of the specimens are the
bullets or foreign bodies surrounded by regular ivory. They
are in every instance inclosed in masses, more or less bulky,
VoLM
Plate, II
ENCLOSED IN THE TUSKS OF THE ELEPHANT. 57
of a substance which, although abnormal in the tusk of the
elephant, is nevertheless well known to the comparative ana-
tomist as occupying the interior of the teeth of some of the
other mammals, and usually considered to be ossified pulp.
It was evident that the pulp had ossified round the bullet, as
the first step towards the separation of the latter from it. In
one specimen the bullet has become enveloped in a hollow
sphere of this substance, on the surface of which the orifices
of medullary canals are situated. In other specimens the
irregular ivory, which surrounds the balls, had become smooth
on its surface, the medullary canals had disappeared, and the
regular ivory had been formed in a continuous layer over the
surface of the mass. In one tusk a cicatrix was seen occupy-
ing the hole through which the ball had passed, a circum-
stance which, when seen in similar specimens, has greatly
perplexed anatomists. It was observed, however, that in
this instance the shot had passed through that part of the
tusk which had been within the socket ; and bearing in mind
that the tusk is an organ of double growth, it appeared pro-
bable that the shot had been plugged up from within by the
ossified pulp, and from without by the continued growth of
cement, without any regeneration of the displaced ivory a
hypothesis which was afterwards verified by examination.
Before proceeding to give a more detailed account of this
interesting process, I shall state very briefly the opinions of
those authors who have written on the subject, so as to ascer-
tain how near they had approached to the truth, and to point
out the fallacies which had led them astray.
Klockner mentions a ball of gold which was found by a
turner of Amsterdam in the substance of an elephant's tusk.
The longitudinal fibres of the tusk surrounded the metal in
an irregular manner, and were separated from the sound ivory
by a concentric chink situated at some distance from the
ball.
58 ON THE MODE IN WHICH MUSKET-BULLETS BECOME
Camper, in the Description Anatomique d'un Elephant
Male, remarks that it is not unusual to see foreign bodies in-
closed, or as it were soldered, into the substance of the ivory.
The same anatomist also figures and describes a bullet which
was inclosed in a very irregular mass of ivory, covered with
long appendages, which were directed parallel to the axis of
the tusk. The metallic bodies in question, he remarks, must
have penetrated across the alveolus into the hollow of the
tusk, and must have remained for a long time in the substance
of the pulpy flesh which fills that cavity, because the ivory
enveloped them on all sides, and would at length have carried
them beyond the alveolus by the increase of the tooth. He
supposes that the nodules which are formed around the balls
and the very incomplete union of their, fibres with the sound
ivory, add weight to this conjecture. Euysch, in his X. The-
saurus, Plate II., figures brass and iron bullets inclosed in
isolated nodules of irregular ivory.
Blumenbach considers the tusks of the elephant to differ
from other teeth, more particularly in the remarkable patho-
logical phenomenon of bullets, with which the animal has
been shot, being found, on sawing through the tusk, imbedded
in its substance in a peculiar manner. He looks upon this
fact as important in reference to the doctrine of a " nutritio
ultra vasa." He mentions a tusk, equal in size to a man's
thigh, in which an unflattened leaden bullet lay close to the
cavity of the tooth, surrounded by a peculiar covering, and
the entrance from without closed as it were by a cicatrix.
From these facts Blumenbach concludes that the elephant's
tusk, when fractured or perforated, can pour out an ossific
juice to repair the injury.
Mr. Lawrence, in his notes to Blumenbach's Comparative
Anatomy, overlooking these cases (one of which is given in
the text of his author) in which cicatrices have been seen
filling up the orifices produced by balls, explains satisfactorily
ENCLOSED IN THE TUSKS OF THE ELEPHANT. 59
enough those instances in which no such cicatrices exist, and
concludes by denying the power of the ivory to throw out
ossific matter, as asserted by Blumenbach.
The author of the Ossemens Fossiles, in his chapter on the
Structure, Development, and Diseases of the Tusks of the
Elephant, after stating that grooves and notches on the sur-
faces of the tusks never fill up, and only disappear from the
effects of friction, allows that musket-balls are found in ivory
without any apparent hole by which they could have entered.
He does not believe that the holes are filled up with ossific
deposition, as Haller and Blumenbach supposed ; but main-
tains that they are never obliterated. He states that the ivory
on the outside of the ball is natural, and that it is only the
bone surrounding it which is irregular. The phenomena are
to be explained, he says, by supposing the balls to penetrate
the very thin bases of tusks in young elephants, so as to enter
the pulps when still in a growing state.
There appear, then, to be two circumstances, regarding
which great doubts still exist first, whether a shot-hole is
ever closed up ; and, secondly, how this is accomplished in a
non-vascular substance like ivory.
In proceeding to consider this subject, two facts must be
borne in mind in reference to a tusk. The first is, that the
two substances of which it is composed, ivory and cement,
undergo no change of form or arrangement from vital action,
after they are once deposited ; the second, that it is an organ
of double growth it is endogenous as well as exogenous, the
ivory being formed from without inwards, the cement from
within outwards.
As there are certain processes which invariably commence
when a foreign body passes through or lodges in the pulp, it
will facilitate the conception of the mode in which a bullet is
inclosed if these be described first. Kecent researches have
proved that the regular ivory of teeth is formed by the cells
60 ON THE MODE IN WHICH MUSKET-BULLETS BECOME
on the surface of the pulp becoming solid from the deposition
of earthy salts in their walls and cavities. It is evident from
this that when a portion of the surface of the tusk-pulp is
destroyed by the passage of a ball, the formation of ivory at
that spot must cease. But we know that the formation of
irregular ivory commences, which indicates the existence of a
healing process in the pulp. The mode in which the wounded
pulp heals cannot be ascertained ; but it is accomplished pro-
bably by effusion and subsequent absorption of blood, depo-
sition of lymph, and regeneration of the peculiar tissue of the
pulp. So far this process is conjectural, but the irregular
ivory, formed by the regenerated pulp, is the subject of ob-
servation. When the ball passes quite across the pulp, the
track heals, but does not necessarily ossify, except in the im-
mediate neighbourhood of the ivory.
There are two exceptions, however, to the non-ossification
of the track of the ball namely, the ossification which takes
place round the bullet, and that which occurs round the
whole or any portion of the track, which may suppurate and
form a sinus or abscess. In both these cases deposition of
irregular ivory takes place, assuming the same characters as
the irregular masses which appear at the two extremities of
the track of the ball through the pulp.
The ossification round the ball generally assumes the form
of a hollow sphere. Its surface exhibits a number of holes
(which are the orifices of medullary canals), and these are
occasionally prolonged through stalactitic-looking processes,
which lie in the direction of the axis of the tooth. The ossi-
fication surrounding an abscess or sinus assumes the appear-
ance of a shell of variable thickness, and directed towards one
or both of the shot-holes.
When thin sections of this irregular ivory are examined
under the microscope, it is seen to consist of a transparent
matrix, in which exist numerous medullary canals, showing
ENCLOSED IN THE TUSKS OF THE ELEPHANT. 61
traces of dried pulp in their interior. From these canals,
which correspond to the Haversian canals of true bone, se-
condary medullary canals, similar to those in the teeth of
certain fishes, radiate. The sides and extremities of these
secondary medullary canals send off numerous minute tubes,
which are true Eetzian tubes, and similar to those in the re-
gular ivory, but not so closely set. These Eetzian tubes have
a general radiating direction, and proceed in irregular wavy
bundles, which sweep past one another without mingling, but
branching particularly at their extremities.
The great central medullary canals are very numerous, and
each of them has its own system of secondary canals and
Eetzian tubes.
These individual systems, when seen in a mass of irregular
ivory, appear globular or spindle-shaped; when viewed in
section, they resemble circular or oval opaque spots with a
hole in the centre. These individual systems, however, are
not isolated ; for they communicate, first, by means of the
central canals, which constitute an inosculating system ; and
secondly, by the ramifying extremities of the Eetzian tubes,
which communicate through the medium of cells more or less
minute, and which are more numerous in some places than in
others.
The formation of the irregular ivory does not go on inde-
finitely ; a limit is set to its increase, and the changes which
ensue at this stage of the process are highly interesting. I
have already mentioned the existence of the orifices of Haver-
sian or medullary canals on the surface of the mass of irregular
ivory. When the further formation of this is to terminate,
these orifices are gradually closed, and appear like imperf orated
projections on the surface. It is evident, therefore, that the
enclosed vascular contents of the canals that is to say, the
ramified processes of the tusk-pulp in the irregular ivory are
cut off from the system. They dry up, and the formation of
62 ON THE MODE IN WHICH MUSKET-BULLETS BECOME
ivory in the interior ceases. The peripheral surface of the
irregular ivory is now, in reference to the general pulp, in the
same relation as the whole internal surface of the irregular
ivory of the tusk. The pulp, therefore, becomes converted
into ivory, not only on the whole internal surface of the tusk,
but also on the surface of the newly-formed mass. The cause
of the formation of the irregular ivory to a limited extent only,
when it exists as an abnormal structure, I have not been able
to ascertain ; but its mode of development and limitation is
highly interesting, and forms a leading distinction between a
tooth and a true bone under similar circumstances.
From this description it is evident that the abnormal ivory
in the elephant's tusk strongly resembles, if it be not identical
with, the peculiar substance which fills the pulp-cavities of
the tusks of the walrus and the teeth of the cetacea, first an-
nounced as a distinct species of dental tissue in a paper read
before this society five years ago by Dr. Knox, and since
minutely described by Ketzius, Owen, and Alexander
Nasmyth. *
This identity of a diseased structure in one animal with a
normal structure in another is remarkable, and must be looked
* Cuvier described this species of dental tissue in the tusk of the walrus,
and compared it to pudding-stone. Dr. Kiiox, in the paper to which I have
referred in the text, affirmed that, in addition to the cement, enamel, and
ivory, a fourth substance namely, the substance described by Cuvier entered
into the formation of many teeth. He stated that, in the teeth of certain
fishes, this substance, or a tissue closely allied to it, constituted the greater
part of their mass ; the other three elements having disappeared or become
greatly diminished in bulk or importance. Ketzius has accurately described
the microscopic structure of this class of dental substances as existing in dif-
ferent animals. Mr. Owen has extended and confirmed the observations of
Eetzius. Lastly, to Mr. A. Nasmyth belongs the merit of having pointed out
the resemblance which this kind of substance (which he denominates ossified
pulp) bears to diseased ivory in the tusks of the elephant, and still more closely
to the substance which fills the pulp-cavity of the aged human tooth. In
ignorance of Dr. Knox's previous observations, he announced this kind of ivory
as a fourth dental substance.
ENCLOSED IN THE TUSKS OF THE ELEPHANT. 63
upon as another instance indicating the existence of a system
of laws regulating the relations between healthy and morbid
tissues laws which have been speculated upon, but have
never been sufficiently investigated by anatomists.
Having now given the anatomical characters of the ab-
normal ivory which invariably surrounds musket-bullets and
other foreign bodies which lodge in the pulps of the tusks of
the elephant, I shall proceed to state the various conditions
under which these enter the organ, and the changes which
ensue.
Foreign bodies enter the tusk in three ways first, through
the free portion of the tusk ; secondly, through that part of
the organ which is contained in the socket ; and thirdly, from
above through the base of the pulp.
First. When the ball hits the free portion of the tusk, if
it only penetrates to a certain depth of the ivory, no change
whatsoever can take place. Neither the cement nor the ivory
can be reproduced. In course of time the hole may be obli-
terated, the ball may be got rid of by wearing down of the
ivory, and the ivory under the hole may be strengthened by
the formation of new substance. When the ball is detained
by the ivory, but penetrates so far as to wound the pulp, the
latter ossifies around it, and the ossified portion sooner or later
becomes enveloped in new ivory. If the ball penetrates the
pulp, the latter ossifies round it, and becomes attached to
the hole in the ivory. If the tusk is growing rapidly,
and the nucleus of pulp-bone does not speedily adhere to
it, the ball will ultimately be situated above the hole. The
ball may also pass across the pulp, and become at last en-
veloped, along with its bony envelope, in the ivory of the
opposite wall.
Second. In the second class of wounds, in which the ball
enters the pulp-cavity through the socket and side of the tusk,
the consequent changes seem to be the following : First,
64 ON THE MODE IN WHICH MUSKET-BALLS BECOME
ossification of the pulp surrounding the ball, and the ultimate
application of the mass to the hole in the ivory, and, as the
latter is necessarily at this part of its extent very thin, the hole
is closed ; second, the application to the hole in the ivory and
to the surface of the ossified pulp in it, of cement formed by
the internal surface of the tusk-follicle. For although the ball
may have removed, or at least torn, the follicle opposite the
hole in the ivory, yet, as the tooth advances in the socket, the
ball will in time arrive at a sound portion of the latter.
One of the specimens exhibited to the Society proves that
the wounded portion of the follicle may perform this duty
sufficiently well. In it the external surface of the cement
exhibits a longitudinal fissure, with smooth rounded edges,
resulting from the defective formation of cement in the
situation of a longitudinal rent or wound in the membrane
of the follicle, through which the ball had entered the
ivory. The hole in the ivory then being plugged up ex-
ternally by cement, and internally by ossified pulp, the case
proceeds as in the last class of wounds the ossified portion
of the pulp surrounding the ball becoming enclosed in true
ivory.
Third. When the foreign body enters from above, without
wounding the tusk, the pulp ossifies round it, and true ivory
envelopes the mass in the usual manner. I have not seen
any morbid ivory which could be referred to wounds of the
class now under consideration ; but a very interesting account
is given by Mr. Comb in the Philosophical Transactions, 1801,
of a tusk in which a spear-head was found, and which could
only have entered the cavity from the base of the pulp. Mr.
Comb describes and figures the ossified portion of the pulp, and
the manner in which it had attached itself to the ivory, and
become covered by it, so as to obliterate partially and to alter
the relative width of the pulp-cavity.
The description I have now given of the changes which
ENCLOSED IN THE TUSKS OF THE ELEPHANT. 65
ensue on wounds of the tusks of the elephant explains many
curious appearances in ivory, and the difficulties anatomists
and physiologists have had in understanding them.
It explains the drawings and descriptions of Klockner,
Ruysch, and Camper ; does away with the necessity of suppos-
ing, with Blumenbach, that true ivory is regenerated, or that it
can throw out ossific juice to produce cicatrices ; and leads us
to believe that Cuvier, in denying the possibility of the obli-
teration of a shot-hole, had allowed himself to be deceived.
All difficulties are got over and contradictions reconciled by
bearing in mind the different circumstances insisted upon in
this paper, namely
1. That a tusk is an endogenous as well as an exogenous
organ.
2. That the pulp forms irregular ivory round foreign
bodies, and at wounds on its surface.
3. That the membrane of the follicle is an important agent
in closing up the holes produced by foreign bodies which pene-
trate a tusk through the socket.
66 ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES.
IV. ON THE SUPEA-EENAL, THYMUS, AND
THYEOID BODIES. PLATE III
WHILE engaged, two years ago, in observing the structure
of the lymphatic glands, my attention was directed to the
thymus, thyroid, and snpra-renal bodies ; and I was led to
frame a hypothesis, which, although afterwards requiring
some modification, has, I conceive, nevertheless enabled me to
detect, if not the real physiological, at least the morphological
signification of these apparently anomalous organs.
My hypothesis was, that the thyroid, thymus, and supra-
renal bodies are the remains of the blastoderma ; the thyroid
being a portion of the original cellular substance of the ger-
minal membrane grouped around the two principal branches
of the omphalo-mesenteric vein ; the supra-renal capsules,
constituting other portions grouped around the omphalo-
mesenteric arteries ; and the thymus, the intermediate portion
of the same membrane arranged along the sides of the em-
bryonic visceral cavity.
Subsequent observations have satisfied me that this hypo-
thesis is essentially correct, with the exception of that part of
it relating to the thyroid, which body I have now ascertained
to be a portion of the membrana intermedia of Eeichert,
which remains in connection with anastomosing vessels
between the first and second aortic arches, or carotid and sub-
clavian arteries.
In the embryo of the sheep, while the branchial clefts are
still open, and for some time afterwards, there is a quantity of
Vol. II
Plate IK
ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES. 67
blastema arranged in minute lobular masses around the ante-
rior parts of the cardinal veins of Kathke, surrounding the
jugular veins and ductus Cuvieri for a short distance behind
the forepart of the Wolffian bodies. Immediately in front of
the Wolffian bodies these lateral masses of blastema are narrow,
being scarcely perceptible on the coats of the cardinal veins ;
but around the ductus Cuvieri they are larger, and differ from
the general texture of the embryo, in having a darker colour,
in containing no fibres, in separating readily from the sur-
rounding parts, and in their lobulated appearance. They
extend forwards nearly to the base of the cranium, and are not
connected across the median plain. They are broadest at the
sides of the heart, and when the pericardium is opened, are
seen through its posterior wall occupying the future situations
of the lungs, which at the period stated exist as two small
lobulated white bodies, projecting from the intestinal tube,
behind and below the heart.
These two lateral masses are the only remaining portions
of the membrana intermedia : the posterior portion on each
side, on the inner aspect of the anterior extremity of the
Wolffian body, becomes the supra-renal capsule ; the enlarged
middle portion and the outer part of the cervical portion
become the thymus ; w r hile the internal anterior part resolves
itself into the thyroid body. These three organs are therefore
at this period continuous with one another on each side of the
middle line, no isthmus having yet been formed. They are
also continuous with the Wolffian bodies ; these bodies, the
supra-renal capsule, the thymus, and the thyroid, forming a
continuous mass, situated in the elongated angular channel,
which stretches from the cranium to the coccyx on the outside
of the intestinal or mesenteric laminae, and between them and
the visceral laminae.
The Wolffian bodies are the last organs formed out of the
membrana intermedia, which assume a special structure. The
68 ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES.
supra-renal capsules, the thymus, and thyroid, retain through-
out their existence the original texture of the blastoderma.
Proceeding therefore in the order of formation as well as
of position from the Wolffian body, I shall state very briefly
what I have observed concerning the mode of development of
the supra-renal capsules, thymus, and thyroid.
In the embryo- of the sheep, in which the branchial clefts
are still quite open, the omphalo-mesenteric vessels well
developed, the liver consisting of an equal-sized lobe on each
side of the intestinal tube, the Wolffian bodies well formed,
the allantois beginning to protrude from the abdomen, and
the umbilical vessels already apparent, there may be seen
between the internal anterior part of the Wolffian bodies and
the aorta at the origin of the omphalo-mesenteric arteries, and
also around the omphalo-mesenteric vein, where that vessel is
passing forward into the liver, a mass of blastema spread over
the internal surface of the fore-part of the Wolffian body, and
arranged in one or more masses between that gland and the
aorta.
In embryos rather more advanced, these masses of blastema
become less distinct, apparently from their increased bulk
causing them to be applied more uniformly over the anterior
extremities of the Wolffian bodies. They may always be
detected by their whiter appearance, and by being destitute
of the cross-markings produced by the ducts of the Wolffian
glands.
It is not till the testes, ovaries, and kidneys have appeared,
that the supra-renal capsules are recognised as distinct organs ;
and their progress after this period need not be considered
further at present.
The cardinal veins of Eathke pass forward along the pos-
terior and lateral part of the Wolffian bodies ; after passing
beyond the blunt anterior extremities of these bodies, each
vein carries with it, or is covered by a thin layer of the bias-
ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES. 69
tema already alluded to as forming at its posterior part the
supra-renal capsule. This portion of the blastema becomes
much larger at the side of the heart, round the ductus Cuvieri,
behind the lateral parts of the pericardium, and in the future
situation of the lungs, which have not yet left their median
position. Each lateral portion of the blastema stretches from
the heart forwards along the internal side of the jugular vein,
par vagum, and carotid arteries. These two anterior portions
of the lateral blastema, from the narrow portion forwards to
the skull, are the lateral portions of the thymus and thyroid,
which have not yet joined across the middle line.
In embryos a little further advanced, the two portions of
blastema join across the trachea in a line extending from the
base of the heart to the lower end of the larynx, which has
now appeared as an oblong oval swelling behind the tongue.
Previous to, and also contemporaneous with, this cross junc-
tion, a change has occurred in the position of the lungs and of
the ductus Cuvieri.
As the lungs proceed in development, they pass in a
direction from behind forwards and from within outwards,
moving from their original median position to a lateral one :
they at the same time increase both absolutely and relatively.
At the same time, a somewhat similar change takes place in
the two ductus Cuvieri. They pass forward so as to appear
to enter the anterior instead of the posterior extremity of the
auricle, becoming in this way the anterior vense cavse, this
change of position being produced apparently by a semi-
revolution of the whole heart, coinciding with its elongation
and the altered arrangement of the bulbous aortse.
Coincident with this change in the ductus Cuvieri is a
corresponding change in the position of the lateral masses of
the blastema. These pass forward, become grouped around
the auricles and anterior venae cavse, and join across the
middle line as already stated ; but a narrow portion, particu-
70 ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES.
larly along the left side, still passes downwards and back-
wards along the cardinal veins, which have now become the
azygos veins.
While these changes in the veins and blastema have
taken place, the lungs have increased in size, and their
roots have taken up their proper position. In consequence of
this change in the position of the pulmonary roots and of
the ductus Cuvieri, the cardinal veins arch over the root of
the lungs in the same manner as the azygos vein of the adult
does.
At the same time the blastema of opposite sides unites, as
has been stated, across and in front of the base of the heart
and root of the neck.
Shortly after this period, the posterior part of the blas-
tema, which has now advanced, as already stated, from the
sides of the chest to the front of the heart, becomes separated
by a narrow neck from the cervical portion. The posterior
part has now become the thoracic portion of the thymus, and
in the embryo of the sheep is largest on the left side, corres-
ponding in this respect to the large size of the left vena azygos
and left vena cava at this period.
The cervical portion of the blastema now begins to exhibit
a separation into the thyroid and cervical portion of the
thymus. This is effected by the absorption of a portion of the
blastema, of a triangular form, a little behind the larynx, the
apex looking backwards, the concave base forwards, so that
the future thyroid presents a crescentic form, its sides being
as yet united to the anterior horns of the thymus, which pass
along the jugular veins.
The thyroid now separates more completely from the
thymus, by the prolongation forwards of the absorption pre-
viously mentioned from the anterior angles of the triangular
portion, so as to separate the thyroid from the anterior horns
of the thymus ; at the same time the posterior angle of the
ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES. 71
absorbed portion passing back so as almost again to separate
the cervical portion of the thymus into two lateral portions.
As development advances the thyroid becomes more com-
pletely separated from the thymus, and the lateral portions of
the cervical part of the latter are united only by the narrow
portion which connects them with the thoracic lobe of the
organ.
At this stage a distinction may be observed, with low
magnifying power, in the texture of the two organs. The
thyroid is more opaque and homogeneous, the thymus consists
of minute granular masses imbedded in a semitransparent
matrix. The component elements of the textures of the two
organs is however identical namely, simple nucleated cells
grouped around dark points, which I am inclined to regard as
centres of nutrition. In the thyroid, these groups are sepa-
rated and connected by a more or less dense highly vascular
areolar texture. In the thymus this texture is weak or
deficient.
After this period no great change occurs in the thyroid
and thymus of the sheep ; the anterior extremities of the
horns of the thymus on each side presenting two bulbous
enlargements near the base of the skull, close to the ganglions
of the vagus.
Four minute white cords may now be seen passing into
the superior, and two into the inferior border of the thyroid.
These are the inferior and superior thyroid arteries, branches
respectively from the first and second branchial arteries.
From these observations it would appear that the supra-
renal capsules, the thymus, and thyroid, are persistent portions
of the membrana intermedia of the germinal area of the ovum,
retaining throughout their existence the original simple
cellular constitution of that portion of the germinal mem-
brane.
I shall now endeavour to explain in how far the observa-
72 ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES.
tions just detailed appear to me to enable us to trace the
functional import and anatomical peculiarities of these organs.
During the first stage of the development of the animal
ovum, digestion and respiration the absorption and prepara-
tion of nutriment are carried on by the blastoderma, a struc-
ture consisting of nucleated cells and of vessels.
The cells, of which the blastoderma consists, are the pro-
geny of that previously occupying the germinal spot of the
ovum, and are continually reproduced and increased in num-
bers by the production of others from the nutritive centres, or
secondary germinal spots distributed over it.
Materials for the nutrition of the blastoderma are derived
from the subjacent yelk. The matter resulting from the solu-
tion of a certain number of the secondary blastodermal cells
that is, of the progeny of the primary blastodermal cells, or
nutritive centres is employed by the nutrient matter of the
remaining secondary or proper blastodermal cells. In this
way " pabulum" is afforded for two purposes the growth of
the blastoderma, and the growth of the embryo itself.
During the early period of the existence of the blasto-
derma, before the circulation has been established, the product
of solution of the elder is at once absorbed by the younger
cells. During the later periods, the product of solution drops
into the incipient loops of the blood-vessels, and so circulates
for purposes of nutrition. This is an instance of primary
lymphatic absorption, and differs in no essential particular
from the same process in the animal further advanced. We
may consider the blastoderma in fact, during the first period
of its circulation, as containing very numerous lymphatic
ducts, instead of a few, as in the more perfect animal.
In the blastoderma, the process by which nutrient matter
passes into the circulation, or the act of absorption, as it is
usually called, is reduced to its most simple form, being con-
temporaneous and also identical with the formation of the
ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES. 73
imperfect capillary network. In the more advanced animal,
when the capillary network is consolidated, the product of
solution of the textures passes or drops into the intercellular
or textural lacunae, which appear to be the radicles of the
lymphatic system ; a system which in the adult communicates
with the blood-vessels only at a few places in the neighbour-
hood of the trunks of the original blastodermal veins.
The blastoderma may be considered therefore not only as
the first form which the being assumes after the commence-
ment of development, and as a basis out of and in which its
higher structures are to be raised, but also, as has been already
stated, the organ of primary digestion that is, of the appro-
priation arid elaboration by the individual of nutritive matter
already prepared, to a certain extent, by another individual or
organ.
All the principal organs and parts of the future being are
formed in, and out of, portions of the blastoderma. The
laminae dorsales, the cerebro-spinal axis, the visceral laminae,
the intestinal tube, heart, and liver, derive their origin from
this source. Their original relation to this part is soon lost
sight of from changes in their positions, but principally from
the increased development of their original blastema, and its
change into the various textures, and from the various arrange-
ment of these textures in the organs.
There are three organs, however, which still retain their
primitive structure after all the other parts of the animal have
undergone their complete development, so as finally to exhibit
no trace of their original simple texture and arrangement.
These organs are the supra-renal capsules, the thymus, and
thyroid.
The structure of each of these three organs is essentially
the same : they consist of masses of nucleated cells. These
cells are grouped around numerous germinal spots arranged
throughout the mass, and which may be supposed to act as
74 ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES.
centres of origin and of nutrition, each for its own group.
The mass of the organ is supplied with blood-vessels to convey
the blood to and from the part, and with lymphatics which
receive the product of solution of the cells, and convey it
back again into the general circulation, whence it was origin-
ally derived.
The account of the structure of the thymus given by Sir
Astley Cooper is so far incorrect, as this organ contains no
reservoirs or cavities in its substance. The cavities exhibited
by Sir Astley Cooper in his drawings and preparations are
the results of modes of preparing. They are artificial cavities
formed by distension, between the somewhat smooth, highly
vascular, and slightly adhering outer surfaces of contiguous
lobules ; the whole organ being at the same time bound
together by a stronger external areolar texture. No milky
fluid is found naturally in these interlobular spaces. Indeed,
Sir Astley Cooper says, that " the best mode of obtaining it is
by cutting the gland into very small pieces and placing them
upon gauze, which being squeezed, the solid is separated from
the fluid part, and the latter escapes through the gauze."
The thymus, from the time it assumes its most perfect
structure till it begins to degenerate into fatty substance, con-
sists of lobes connected by areolar fibres, without cavities or
ducts, formed of nucleated cells grouped around germinal
spots, deriving matter for the formation of their cells from
arteries passing into it, and being relieved of its venous blood
by returning veins, being plentifully supplied with lymphatics,
which do not communicate with the supposed reservoirs, as
has been suggested, but appear to take their origin, as in other
parts, by intercellular lacunae, in which the walls seem gradu-
ally to lose themselves, as the ducts of the liver are lost
among the secreting cells of that organ.
The thyroid body possesses a structure which is essentially
the same as that of the thymus. It differs from the thymus
ON THE SUPRA-RENAL, THYMTJS, AND THYROID BODIES. 75
in not being divided into lobules, in having the groups of cells
of which it consists separated from one another by moderately
strong capsular membranes, and in being more vascular, the
anterior and venous trunks being much larger.
The supra-renal capsules also consist of nucleated cells
grouped round germinal spots, and arranged, not in lobules,
but in columns passing towards the surface of the organs ; an
arrangement corresponding to the radiating direction of the
veins, and the converging arteries of these parts. The supra-
renal and thyroid bodies are more vascular than the thymus
from being developed around large arteries, while the thymus
is in connection with smaller trunks, the former being de-
veloped in connection with the first and second aortic arches
and the omphalo-mesenteric vessels ; the latter in connection
with the internal mammary arteries and other small thoracic
and cervical branches. The greater density of the areolar
capsule of the thyroid may probably be explained by this in-
creased vascular supply.
That portion of the membrana intermedia which is sepa-
rated from the rest of the membrane, and included in the body
of the embryo by the umbilical constriction, and which has
not already been devoted to the formation of the heart, liver,
pancreas, and external portion of the intestinal canal, is found
massed along the trunks of the primitive venous system, the
sides of the arches of the aorta, the terminal portion of that
vessel, and the origins of the omphalo-mesenteric arteries.
The portions of the membrana intermedia which are last
of being converted into special organs, the Wolffian bodies, are
the parts which project one on each side of the aorta, along
the posterior part of the cardinal veins of Eathke, between
the intestinal plates and visceral laminae.
The portions of the membrana intermedia which remain
between the upper extremities of the Wolffian bodies and the
heart and liver, and which surround the origins of the om-
76 ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES.
phalo-mesenteric arteries, do not become converted into organs
of special structure, but retain during life the original consti-
tution of the membrana intermedia of the blastoderma, and
increase rapidly in the embryo, constituting the supra-renal
capsules. Whatever doubt may be entertained as to the exact
functional import of these bodies, the identity of their ana-
tomical constitution with that of the blastoderma is sufficiently
evident, and their morphological signification appears to be
equally so.
That portion of the membrana intermedia which is situated
between those two aortic arches, the extremities of which
become the carotid and subclavian arteries, remains during
life as the thyroid body. It receives its blood from the first
and second aortic arches by two large trunks on each side, the
superior and inferior thyroid arteries.
That portion of the membrane which passes in two parts
from near the base of the cranium back as far as the ductus
Cuvieri and anterior portions of the veins of Eathke, and
which are united and concentrated in front of the heart by
passing from behind forwards, in harmony with corresponding
motions of the neighbouring part, becomes the thymus.
The structure of these three organs is identical with that
of the blastoderma. Their probable function namely, to
prepare by the action of their nucleated cells, and to throw
into the vascular system, a matter necessary for the nutrition
of the animal during the period of its active growth a func-
tion which the observations and opinions of the majority of
physiologists have assigned to them is also essentially the
same with that of the blastoderma.
The question as to the exact or intimate nature of the
function of these organs can only be answered by further in-
quiries in chemical physiology. It appears to me to be suffi-
cient at present to insist that their function, as deduced
from their structure and anatomical relations, is similar to
ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES. 77
that performed by the blastoderma, whatever the exact nature
of that function may be.
I have therefore been led to consider the supra-renal
capsules, the thymus, and thyroid, as organs essentially similar
in structure ; as developments of the remains of the blasto-
derma, being formed of a continuous portion of that part
situated along each side of the spine, from the Wolffian bodies
to the base of the cranium, the supra-renal capsules being de-
veloped in connection with the omphalo-mesenteric vessels,
the thymus to the jugular and cardinal veins, and ductus
Cuvieri ; and the thyroid to the anastomosing branches of the
first and second aortic arches, as organs performing functions,
whatever these may be, analogous to those of the blastoderma,
differing from them only in this, that the blastoderma not only
elaborates nourishment for the embryo, but absorbs it also
from without that is, from the yelk ; whereas the three organs
in question only elaborate the matter which has already been
absorbed by the other parts, and is now circulating in the
vessels of the more perfect individual.
78 ON THE MORPHOLOGICAL RELATIONS
V. ON THE MORPHOLOGICAL EELATIONS OF
THE NEEVOUS SYSTEM IN THE ANNULOSE
AND VEETEBEATE TYPES OF OEGANISATION.*
THE term annulose is employed provisionally, and in a
morphological sense, as including all animals possessing a
ganglionic nervous collar and axis, and presenting, at the
same time, more or less distinct indications of a segmented
structure of body.
Physiologists appear generally inclined to consider the
central portions of the annulose and vertebrate nervous sys-
tems as modified forms of the same arrangement. These
forms are held to possess a general similarity of structure,
and correspondence in function ; and the ganglionic collar
and axis of the annulose are assumed to be homologous either
with the cerebro-spinal axis, or with the series of ganglions
on the posterior roots of the spinal nerves, or with the system
of sympathetic ganglions of the vertebrate animal.
In my own examination of this subject I have been
strongly impressed with the necessity of determining the
morphological character of the cesophageal collar, and the op-
posite positions of the so-called brain and abdominal gan-
glionic cord, before any satisfactory advance could be made
in ascertaining the relations of the two forms of nervous
system. The apparent morphological difference between
* This and the two following papers were read to Section D at the Chel-
tenham Meeting of the British Association, Aug. 5-12, 1856, and were pub-
lished in abstract in the Edinburgh Philosophical Journal, Jan. 1857. EDS.
OF THE NERVOUS SYSTEM. 79
them does not appear, in the estimation of physiologists
generally, to present that obstacle to a satisfactory com-
parison which its essentially fundamental character would lead
us to expect. The difficulty has, however, been clearly stated
by Professor Owen, who, in discussing the relations of the endo-
and exo-skeletons in his Lectures on Fishes, page 21, ed. 1846,
says " Geoffroy St. Hilaire thought it needed but to reverse
the position of the crustacean to turn what had been
wrongly deemed the belly upwards in order to demonstrate
the unity of organisation between the articulate and ver-
tebrate animal. But the position of the brain is thereby
reversed, and the alimentary canal still intervenes in
the invertebrate between the aortic trunk and the neural
canal."
I must here premise, that while I hold the general mor-
phological relations of the annulose and vertebrate ner-
vous systems to be identical, I do not consider these two
types of organisation to be mutually reducible. On the con-
trary, they are fundamentally distinct, presenting differences
which demand careful consideration. It is, nevertheless,
incumbent on the morphologist to ascertain in what re-
spects they correspond, so as to determine their distinctive
limits.
My earlier conception of the morphology of the annulose
nervous system was based on that of Carus. I conceived that
each segment of the annulose animal contains potentially an
annular nervous arrangement, set in a plane at right angles
to the axis of the segment, or longitudinal axis of the animal ;
that the only complete nervous ring is that one through
which the oesophagus passes ; that the ganglions on this ring
are arranged in the various forms of superior, lateral, and in-
ferior oesophageal masses ; that the nervous rings in the post-
cephalic segments are all incomplete above, and have their
ganglions united into a single or double mass below ; and
80 ON THE MORPHOLOGICAL RELATIONS
that all the rings are united by a series of longitudinal abdo-
minal commissures. According to this view, the cesophageal
collar, with its superior, lateral, and inferior ganglions, is
homologous with each pair of segmental nerves, and the cor-
responding abdominal ganglionic centre; the cesophageal
collar being in a plane parallel to those in which the post-
cephalic ganglions and their pairs of nerves are situated, but
at right 'angles to the line of the series of abdominal gan-
glions.
I first recognised what I believe to be the real morpho-
logical relations of the annulose nervous system during the
delivery of a course of lectures on Invertebrate Anatomy in
1849 ; but more fully and completely during courses on the
Anatomy of the Mollusca in 1850, and on the Anatomy of
the Crustacea in 1851.
I now perceived that the fundamental difference between
the morphological relations of the annulose and vertebrate
nervous systems, consists in the position of the mouth.
I saw that the entire axis or central portion of the nervous
system extends along the neural aspect of the body in both
types of organisation ; but that while, as is well known
although its morphological importance does not appear to
have been perceived the vertebrate mouth opens into the
haemal, the annulose mouth passes through the neural aspect
of the body.
In the annulose animal, therefore, the buccal entrance
interferes with the nervous axis passing up between the two
lateral halves of one of its longitudinal commissural or inter-
ganglionic cords, so as morphologically to divide the con-
tinuous axis into a pre-stomal and a post-stomal portion.
These relations are most satisfactorily seen in the crus-
tacea, in which the so-called brain, or supra-cesophageal gan-
glion or nervous mass, is actually in front of the mouth,
and not above it.
OF THE NERVOUS SYSTEM. 81
In insects, annelids, and mollusca, the bulk of the buccal
mass, and other necessary modifications of the oral apparatus,
elevate the so-called brain, curving upwards the morpho-
logical axis of the body of the animal.
By comparing the indications of segments in front of the
mouth, and their corresponding diverging appendages, with
the arrangement and distribution of the nerves given off from
the so-called brain, it appears very evident that this brain is
the aggregate of the segmental nervous centres in front of the
mouth.
In like manner indications afforded by the segments, and
their appendages immediately behind the mouth, enable us to
determine whether the so-called sub-cesophageal ganglionic
mass is a single segmental ganglion, or an aggregate of antero-
posteriorly united segmental ganglions.
In this way I was enabled to perceive that the axis of the
nervous system of the annulose animal does not consist of a
supra-oesophageal mass, of an cesophageal collar, of a sub-
oesophageal mass, and a continuous sub-intestinal ganglionic
chain ; but of a continuous line of connected and serially
homologous ganglions situated in the mesial line of the
neural aspect of the body.
The annulose, like the vertebrate animal, is developed
with its nervous axis turned away from, and its haemal axis
applied against, the vitellary mass.*
* From the passage in his lectures already quoted, Professor Owen would
appear to consider the dorsal heart, with its anterior and posterior arterial
trunks in the decapod crustacean, and consequently the dorsal vessel in the
insect, arachnidan, and annelid, as corresponding to the thoracic, abdominal,
and caudal aortic trunk of the vertebrate animal. On this supposition only
can we understand his assertion, that when the so-called belly of the crus-
tacean is turned upwards, its alimentary canal is still interposed between the
aortic trunk and the neural canal. Embryology, comparative anatomy, and
physiology, appear to me, however, to afford ample proof that the cardiac -
arterial dorsal trunk of the annelid, crustacean, insect, or arachnidan, is ho-
mologous, not with the sub-spinal aorta of the vertebrate, but with the pri-
G
82 ON THE MORPHOLOGICAL RELATIONS
But, in the course of development, the mouth of the ver-
tebrate opens through the surface applied against the vitellary
mass, whilst that of the annulose animal passes through the
aspect turned away from it. The vertebrate mouth is haemal,
the annulose mouth neural.
Rathke formerly described the pituitary body as origi-
nating in a diverticulum passing up from the pharyngeal
mucous membrane through the basis of the embryo skull.
I at one time conceived it to be probable that the pituitary
body, and the mucous tube, in which, according to Eathke,
it originates, might be indications in the vertebrate of a
structure which, in the annulose animal, is converted into
the mouth. This presumed neural alimentary passage may
be conceived as passing up between the bodies of the anterior
and posterior sphenoid bones into the Sella Turcica, along the
course of the infundibulum to the third ventricle of the brain,
and through the cavity of that organ to its upper surface
behind the cerebellum, thus leaving the origins of the nerves
of smell and vision in the pre-stomal portion of the organ,
while the origin of the nerve of hearing would remain in the
medulla oblongata or post-stomal portion of the cephalic
nervous mass. The arterial circle of Willis, and other pecu-
liar arrangements at the base of the skull and brain, appeared
to support the view taken. I shall not, however, pursue this
hypothesis further, because, from the observations of Eeichert,
we know that the base of the cranium is not perforated in the
embryo, and that the supposed canal or diverticulum was an
incorrect interpretation of the peculiar appearances pro-
mordial cardiac-arterial tube in all the forms of the embryo vertebrate, and,
consequently, with the heart and trunk of the branchial artery of the fish. If
this, then, is the real homology of the " aortic trunk " of the crustacean, and
if its "brain" is in fact only a pre-stomal portion of its nervous axis, the
French anatomist was quite correct in his general morphological statement,
although he was not legitimately entitled at the time to employ the illus-
tration.
OF THE NERVOUS SYSTEM. 83
duced by the curvature downwards of the early Mammalian
head.*
If I have determined aright the morphological relations of
these two forms of nervous system, we shall have advanced a
step in our conceptions of the anatomico-physiological re-
lations of the annulose and vertebrate animals, and this
without losing sight of the fundamental differences, develop-
mental and structural, between them. The researches of
Milne-Edwards, and of Newport and others, on the annulose
nervous axis may thus be physiologically associated with
those of Wagner, Schroeder Van der Kolk, Owsjannikow,
Jacobowitsch, and Kupffer, on the cerebro-spinal axis ; and
we may now legitimately employ the annulose animal in the
morphological investigation of the vertebrate skeleton.
Omitting, for the present, the consideration of the mode
in which the nervous systems in the Tunicata, Eotifera, and
Entozoa, are reducible to the typical annulose form, I pro-
ceed to make some general morphological statements, based
to a certain extent on the principle indicated in this, and
introductory to the two following communications :
1. The morphology of any one organic system in the
annulose or vertebrate animal, cannot be safely or satis-
factorily investigated, without constant reference to the
others. That it must be so is evident from the fact, that all
the organic systems are dependent on one another, in the
constitution of the organism.
2. All sound morphological inquiry demands constant
reference to the series of embryo, as well as of adult forms.
3. As morphology deals with forms and relations of posi-
tion, it demands a careful selection of terms, and a methodised
* I have introduced the hypothesis of a vertebrate neural mouth (cast aside
in the course of my examination of the subject), because I believe it will be
found to involve relations of importance in the anatomico-physiological in-
vestigation of the pre-stomal and post-stomal portions of the vertebrate and
annulose cephalic nervous masses.
84 ON THE MORPHOLOGICAL RELATIONS
nomenclature. All terms involving more or less than their
morphological application demands, must be avoided. Terms
derived from other departments of the science, and having
therefore an established technical meaning, have invariably
produced misconception, when transferred for morphological
purposes.
Influenced by these considerations, and satisfied that the
annulose and vertebrate types of organisation, although
fundamentally distinct, present parallel forms of structure,
and must consequently be closely linked together in morpho-
logical inquiry, I have to suggest a more extended and pre-
cise system of nomenclature for this department of the
science.
In the annulose and vertebrate types of organisation, the
body of the animal consists of a linear ^3 133 of segments. To
the constituent segment, with its diveig' '<* appendages, I
apply the term somatome (rf/Aa, repvu).
For the purpose of avoiding circumlocution, and of sup-
plying a term for a generalised conception, and thereby facili-
tating morphological description, without encroaching on
zoological nomenclature, I denominate a segmented animal,
whether annulose or vertebrate, an entomosome an entomo-
somatous animal (gVo//,os, <rw,aa).
As the constituent somatomes are invariably arranged in
groups, in each of which they are more or less modified in
form, or fused together, I find syssomatome (<rt>, <rcD/-c, ripvu) a
convenient designation for such a group. A typical crusta-
cean presents a cephalic, a thoracic, and a caudal syssoma-
tome, in each of which there are seven somatomes twenty-
one in all.
The constituent somatomes lie in planes at right angles to
the morphological axis of the body, and are symmetrical in the
transverse, but unsymmetrical in the perpendicular direction.
They are, however, not only unsymmetrical in their upper
OF THE NERVOUS SYSTEM. 85
and under surfaces, but the surfaces so named in the annu-
lose are morphologically distinct from those similarly desig-
nated in the vertebrate animal. The annulose animal moves
on the surface which was turned away from the vitellary mass
during development ; the vertebrate animal moves on the
surface which was applied to it during development. As the
axis of the nervous system is formed at the surface turned
away from the vitellary mass, and the axis of the vascular
system is formed at the surface applied to it in both types of
organisation, I employ, as morphological designations, the
term neuropod (wugov, vovg) for an annulose, and hsemapod
(aTpa, vovg) for a vertebrate animal.
The mouth of the entomosomatous animal is invariably
situated between two somatomes, so that a certain number
of somatomes are interposed between it and the anterior
termination of the body. As the mouth is only one of a
number of openings situated between somatomes, I find such
openings conveniently distinguished as metasomatomic.
The mouth of the neuropod is a neural, that of the hsema-
pod a haemal metasomatomic opening.
As the somatome exhibits in its structure corresponding
segments of certain or of all the organic systems, I have found
the following morphological terms extremely convenient in
referring from the segment of one organic system to the cor-
responding segments of the others.
For the entire framework of an entomosome, whether this
framework be developed in its integument or in its interior
whether it be fibrous, cartilaginous, or osseous I employ the
term sclerome (VxA^g, with the termination of completeness).
To a segment of the sclerome I apply the designation sclero-
tome (tfxtojgte, refAvu). An aggregate of more or less modified
sclerotomes I name a syssderotome (ffuv). Making use of my
former illustration, the sclerome of a typical crustacean con-
sists of twenty-one sclerotomes grouped in three syssclerotomes.
86 ON THE MORPHOLOGICAL RELATIONS
Again, the sclerome of a mammal consists of a number of
sclerotomes, grouped into the cephalic, cervical, thoracic, lum-
bar, sacral, and caudal syssclerotomes.
For the muscular system I employ the terms myome, myo-
tome, symmyotome ; for the nervous system, neurome, neuro-
tome, synneurotome ; for the vascular system, hcemome, hcema-
tome, synhcematome ; for the morphologically as well as physio-
logically important digestive system, with its segments, and
groups of segments, peptome, peptatome, and synpeptatome, etc.
Till very lately, I had not met with any indication of the
actual morphological character of the so-called supra-ceso-
phageal ganglion in the works of British or foreign physiolo-
gists. I have now found, in an obscure corner of Von Baer's
works, sufficient evidence that he had recognised its pre-stomal
character. His statements are contained in a single paragraph,
which forms an episode in the middle of the second corollary
of the fifth scholium of his work on the development of the
chick in ovo. Von Baer holds, with E. H. Weber and Trevi-
ranus, that the nervous axis of the neuropod is homologous
with the series of ganglions on the posterior roots of the
spinal nerves of the hsernapod ; and he considers the " supra-
cesophageal" ganglion to be the homologue of the Gasserian
ganglion ; but he adds, " Peculiar stress is laid on this, that
it (the supra-cesophageal ganglion) lies above (liber) the
mouth. This appears to me to be a false view of the matter ;
it lies, in fact, in front of (vor) the mouth/' He gives a
diagram of the arrangement, and proceeds : " The following
sketch will make it evident that the so-called brain of the
insect has the same signification as the posterior ganglions ;
and the cesophageal ring is only a secondary formation,
dependent on the breaking through of the mouth, permitted
by the symmetry of the structure, and the necessary con-
nection of the ganglions."
It is somewhat remarkable that no one even of Von
OF THE NERVOUS SYSTEM. 87
Baer's own countrymen, has, so far as I know, made any
allusion to this passage. Indeed, he does not appear to have
been himself aware of the value of the observation, as he
adduces it merely in the form of an argument in illustration
of another subject, and does not again recur to it. For my
own part, having ascertained, on independent grounds, and
publicly taught and illustrated for some years, the principle
stated in this communication, I feel gratified in having this
opportunity of rescuing from temporary oblivion, and of
adducing in support of my own statement of the principle, the
original announcement of it, made twenty-eight years ago, by
one of the most philosophic of modern anatomists.*
* I accidentally discovered, a few weeks ago, that Professor Huxley had
published translations of portions of Von Baer's works in the Scientific Memoirs
for 1853. This judicious selection contains the passage referred to in my paper.
(Dec. 4, 1856.)
88 ON THE MORPHOLOGICAL CONSTITUTION OF
VI.
ON THE MOEPHOLOGICAL CONSTITUTION OF THE
SKELETON OF THE VEETEBEATE HEAD.
IN an abstract which professes to give only the general
results of my own investigations, I cannot enter into such
critico-historical details as would be necessary were the
corresponding or opposite results obtained by other inquirers
to be in every instance brought forward. I am therefore
obliged at present to state, in a somewhat dogmatic form,
the results which I conceive I have obtained, and the views
I have been induced to take of a subject in itself extensive
and difficult, and one to which so many distinguished anato-
mists have devoted themselves.
Nature of the Subject. The framework of the vertebrate
head is a syssclerotome that is, a group of sclerotomes
variously modified, and more or less connected, so as to form
a distinct whole. The points to be determined are the number
and modifications of the sclerotomes in the various forms of
vertebrate head. There are, however, some preliminary
questions which must be briefly examined.
The Source and Mode of Origin of the Sclerome in the Ver-
tebrate Embryo. The knowledge we at present possess of the
source and mode of origin of the vertebrate sclerome is the
result of the successive researches more particularly of Pander,
Von Baer, Bathke, Eeichert, and Eemak, on the development
of the blastoderma.
Von Baer, while he adopted the doctrine of Pander re-
THE SKELETON OF THE VERTEBRATE HEAD. 89
garding the so-called " serous " and " mucous layers/' took a
somewhat modified view of the " vascular layer," and directed
attention more particularly to the " dorsal " and " ventral
folds" of the blastoderma, in connection with the " corda
dorsalis," as fundamental embryological characteristics of the
vertebrate type of organisation.
Among the numerous results of the researches made by
Kathke in every department of embryology, there are two
which bear particularly on the present subject. These are
his early discovery of the so-called branchial clefts ; and his
later recognition of the fact that the series of quadrilateral
bodies on each side of the " corda dorsalis," instead of being
the rudiments of vertebrae, contain potentially the germs not
only of these bones, but of the dorsal muscles, and "probably"
of spinal nerves.
Eeichert supplemented the previous observations of Eathke
on the development of the " branchial " or " visceral laminse,"
and of the nasal and maxillary portions of the face.
Finally, Eemak has ascertained, on independent grounds,
that each pair of the dorsal quadrilateral bodies, usually con-
sidered as the rudiments of vertebree, becomes developed
superiorly into a right and left muscular plate, and inferiorly
into a pair of spinal nerves, with their ganglions, along with
the rudiments of a vertebra and pair of ribs, the nerves
being in front of the sclerous elements. In the course of
development a change takes place in this " primordial ver-
tebral system." The rudiments of the vertebral arch and
ribs move backwards, from their original site under the
posterior margins of the overlying muscular plates, to the
anterior margins of the pair of muscular plates immediately
behind, and become united to both pairs. A transverse divi-
sion takes place at the same time in the rudimentary central
masses of each of the primordial vertebrae. These changes
constitute a new order of parts the order or arrangement of
90 ON THE MORPHOLOGICAL CONSTITUTION OF
the " permanent vertebral system." Thus, the products of the
development of a single primordial vertebra are 1. A pair
of spinal nerves, with their ganglions ; 2. The vertebral arch
and pair of ribs immediately behind this pair of nerves ; 3.
The anterior part of the body of the vertebra to which this
arch and ribs are attached ; 4 The intervertebral disk in
front of it ; 5. The posterior part of the body of the vertebra
in front ; and, 6. The group of spinal muscles between these
two vertebrae. The bones, muscles, and nerves of the abdo-
minal and thoracic wall are formed by an extension down-
wards, and adhesion of the lower or costal portion of the
"primordial vertebral system" to the inner surface of the
external of the two layers into which the " primary abdominal
wall " divides. This outer or adherent layer of the " primary
abdominal wall" becomes the areolar layer of the integument,
and enters into the formation of the limbs. The inner layer,
separated from the outer by the pleuro-peritoneal space, forms,
with its fellow of the opposite side, the Wolman bodies, re-
productive glands, spleen, permanent aorta, mesentery, and
the muscular and serous covering of the alimentary tube.
From these remarkable observations of Kemak, it would
appear that the sclerome of the hsemapod, from the anterior
part of the neck backwards, originates as a series of in-
dependent sclerotomes, and that, contemporaneously with
each sclerotome, a corresponding myotome and neurotome
take their rise in a common primordial segment of blastema.
The cephalic portion of the early vertebrate embryo is
peculiar, more particularly, according to Eemak, in the non-
appearance of distinct " primordial vertebrae," and of the
subsequent changes which result from their development.
The great divisions of the brain and of the cerebral nerves
indicate, indeed, the segmented character of the entire struc-
ture, but I am inclined to believe that, in the present state of
the subject, these indications are not to be depended on for
THE SKELETON OF THE VERTEBRATE HEAD. 91
the determination of the segments of the embryo or adult
head. It appears to me that the segmented structure of the
brain is to be looked for, not in its greater masses those
developments on its upper surface in which it differs from
the spinal cord, and by the possession of which it becomes a
brain but in the series of groups of ganglion-cells, the
nervous centres of the cerebral nerves, whatever the typical
number of these may be, arranged along its base, and strictly
homologous with the groups of ganglion-cells which un-
doubtedly constitute the morphological segments of the
spinal cord.
The " visceral " or " branchial laminse " afford, in the pre-
sent state of the subject, a more secure embryological basis
for the determination of the segments of the head. The so-
called " first visceral lamina/' the one in which the mandi-
bular arch., is developed, and the two succeeding " visceral
laminse," those in which the anterior and posterior segments
of the hyoid of mammals and birds are formed, must be looked
upon as embryological indications of three cephalic segments.
On the under-surface of the forepart of the embryo head,
in front of the so-called " first visceral lamina," there are five
processes, in which are developed the palate and pterygoid,
the maxillary, malar, and lachrymal, the intermaxillary and
nasal bones. The first of these processes on each side extends
obliquely forwards from the " first visceral lamina " towards
and under the eye. It is the so-called " superior maxillary
lobe." The second process on each side the " lateral frontal
process" of Eeichert passes down in front of the eye, the
eye being situated in the cleft between it and the former
process. The fifth process is situated in front, and in the
median line. It is the " anterior frontal process " of Eeichert.
The clefts or notches between this process and the "lateral
frontal process " are considered by Eathke and Eeichert to be
the external nostrils.
92 ON THE MOEPHOLOGICAL CONSTITUTION OF
Now, in regard to the so-called " superior maxillary lobes/'
it is clearly established that the palate and pterygoid bones
are formed in them, but there is no sufficient evidence that
they contain the germs of the superior maxillary bones. No
traces of the superior maxillary bones appear until these so-
called " superior maxillary lobes" have extended forwards, and
united with the "lateral frontal processes" and the "nasal
process," and until the maxillary margin has become con-
siderably extended. I am, therefore, of opinion that the
"lateral frontal processes" of Eeichert are, in fact, the real
maxillary lobes, and contain not only the germs of the
lachrymal, but those also of the maxillary and malar bones.
This view of the place of origin of the superior maxillary is
in accordance with the adult relations of these bones. The
position of the superior maxillary is in front of the eye ; the
orbit being, in fact, an expanded cleft between it and the
palate bone.
Again, the nasal bones of the mammal are formed in the
upper part, and the intermaxillary bones in the lateral angles
and palatal lobes of the " anterior frontal process." The notch
or cleft on each side of this process cannot therefore become
the external nostrils, for these are not situated in the mammal
behind the intermaxillary bones, but in front of them. From
these circumstances, I am inclined to consider the external
nostrils of the mammal to be formed by the transverse union of
the palatal lobes of the " anterior frontal process," and by the
formation of the cartilages of the external nose in the mesial
portion of the free margin of that process.
Embryologists generally consider the so-called superior
maxillary lobes to be the upper portions of the " first visceral
laminae" bent forward, and the "lateral" and "anterior
frontal processes" to be superadded structures in no way
related to the " visceral" or * branchial laminae." It appears
to me, however, that the general aspect, the relations, and the
THE SKELETON OF THE VERTEBRATE HEAD. 93
changes undergone by them in development, prove these
parts to be serially homologous with the " visceral laminae,"
and to be, like them, indications of the segmented structure of
the head in front of the so-called first visceral arch. The so-
called superior maxillary lobes indicate a segment of which
the palate and pterygoid bones are elements. The " lateral
frontal" indicate a second segment, containing the maxillary,
malar, and lachrymal bones. The external margins and angles
of the "anterior or frontal processes" indicate an inter-
maxillary segment ; and the development of the mesial part
of the same process into the cartilages of the nose indicates a
segment probably only fully developed in the mammalian
head.
In addition, therefore, to the " visceral laminae" behind
that one in which the mandibular arch is formed, there would
appear to be a series of less developed " visceral laminae" in
front of it, all of which, in addition to other structures, give
rise to haemal arches of the sclerome, and indicate a number
of corresponding sclerotomes.
Of the Primary or Fibrous Sclerome. The bones and
cartilages to which, from their palpable character, the atten-
tion of anatomists has been hitherto chiefly directed, are parts
only of 'the vertebrate sclerome. They are imbedded in a
continuous fibrous matrix, which, variously modified, binds
them together, and co-operates in their general economy and
functions. This matrix forms a more extensive, and, in some
respects, a more important element of the sclerome in the
lower than in 'the higher vertebrata ; and if viewed in the
former in connection with its early stages of development in
the embryo, it will be found to be arranged on the plan of the
"primordial vertebral system." It is most satisfactorily
studied in the fish, and articularly in those forms in which
the bones and cartilage are feebly developed. The fibrous ele-
ment of the sclerome forms the sheath of the " corda dorsalis"
94 ON THE MORPHOLOGICAL CONSTITUTION OF
in the lancelet, and envelopes the column formed by the
bodies of the vertebrae in other fishes. It then bounds the
neural and haemal cavities, and from these cavities passes in
the mesial plane above and below to the neural and haemal
margins of the body. Corresponding cartilaginous and osseous
parts are imbedded in these fibrous neural and haemal laminae.
From the right and left sides of this deep or central system of
fibrous laminae, other laminae extend outwards between the
myotomes, and are connected to the deep fibrous layer of the
integument. The bones usually distinguished as " additional
ribs," "upper ribs," "epipleural spines," "diverging appendages,"
are imbedded in these metamyotomic laminae ; and as the class
of radiating bones to which these so-called additional ribs be-
long maybe conveniently distinguished as actinapophyses (axrts-
ftog), I apply the term actinal to the metamyotomic fibrous
laminae of the sclerome. As those dermal bones or plates which,
from their histological as well as their teleological characters,
certainly constitute elements of the sclerome, are formed in
the layer of the integument to which the actinal sclerous
laminae are attached, this integumentary fibrous structure
must be considered as constituting a dermal sclerous lamina,
and so completing the fibrous portion of the sclerome.
The sclerome thus consists fundamentally of a fibrous
structure, which surrounds the " corda dorsalis," bounds the
neural and haemal cavities, forms a mesial septum above and
below, separates the myotomes from one another, and, under
the integument, envelopes the deeper parts.
The Development of Cartilaginous and Bony Elements in
the Fibrous Sclerome. The immediate development of certain
bones from or in a fibrous matrix, and of others in cartilage
previously formed in it, has given rise, among other questions,
to one as to whether the former are to be included in the
vertebrate system of bones. Now, while I admit the import-
ance of the embryological and histological facts which the
THE SKELETON OF THE VERTEBRATE HEAD. 95
discussion of this question has afforded, I am inclined to think
that a histological bias has influenced both the views which
have been taken of it. Why certain bones originate in a
fibrous matrix, why others originate in cartilage which has
been previously formed in the same matrix, are questions of
undoubted importance, but which at the same time cannot
legitimately be put in opposition to the unity of the fully-de-
veloped sclerome.
Of the Cartilaginous and Bony Elements, and of the general
Morphological Constitution of the Sclerotome. A sclerotome is,
fundamentally, a segment of the fibrous sclerome, and the
series of fibrous sclerotomes is indicated by the actinal laminae,
each of which, for reasons to be afterwards stated, ought pro-
bably to be considered as potentially double that is, as con-
sisting of two layers, one belonging to the sclerotome behind,
the other to the sclerotome in front.
The fully developed heemapod sclerotome is therefore a
fibrous structure, in which all the cartilaginous and osseous
parts are formed and imbedded. With regard to these carti-
laginous or osseous elements, I shall at present only direct
attention to certain points which bear on the constitution of
the sclerotomes of the head. In doing so, I must bear testi-
mony to the general applicability and convenience of the
terms employed by Professor Owen to designate the elements
of his typical vertebra, venturing to suggest modifications in
their application only where I am compelled to differ from
him in regard to the relations of the elements themselves.
The term " centrum " is highly useful as a designation for
the cartilaginous or osseous mass formed around the " corda
dorsalis," whatever the constitution of that mass may be.
The neurapophyses or hard parts developed in the lateral
neural laminse are " typically " two at least on each side. Not
only are there two on each side in the trunk sclerotomes of
certain cartilaginous and probably osseous fishes ; but there
96 ON THE MORPHOLOGICAL CONSTITUTION OF
are two on each side in certain cephalic sclerotomes in at least
fishes and reptiles. Professor Owen admits one neurapophysis
only on each side of his typical vertebra. He accounts for the
additional pair in the spine of the sturgeon on the principle
of "vegetative repetition," while the additional elements in
the neural arches of certain cephalic vertebrae he at one time
considered as parapophyseal, and latterly as diapophyseal
elements. But it appears to me that the principle of " vegeta-
tive repetition " is out of place in a morphological question ;
and a parapophysis cannot, according to Professor Owen's
archetype, be intercalated between a neurapophysis and a
neural spine, nor can a diapophysis become an independent
element.
The superior or posterior spinous process, " neural spine,"
or (as a more convenient general designation) metaneurapo-
physis, is developed in the mesial neural fibrous lamina. As
this element is situated in the mesial plane, it is potentially
double, and its right and left halves become depressed and
more or less flattened out in the cephalic sclerotomes. With
the neurapophysis it completes the neural arch.
The cartilaginous or osseous elements developed in the
lateral and mesial haemal laminse of the fibrous sclerotome
constitute the haemal arch. The fundamental character of the
inferior or haemal arch, as I understand it, consists in this,
that its constituent elements take their rise at or close to the
inner surface of those " ventral laminae" or "folds" in the
embryo, which form the lateral and inferior walls of the vis-
ceral chamber. Every haemal arch, therefore, within the
antero-posterior range of the alimentary tube must, according
as it is more or less developed, necessarily inclose that tube
more or less completely. Accordingly, no arch within the
range of that tube, if it excludes the tube, can be considered
as a haemal arch, merely because it incloses great blood-vessels.
Again, before any arch beyond the range of the alimentary
THE SKELETON OF THE VERTEBRATE HEAD. 97
tube can be considered as a proper haemal arch, its development
must have been ascertained, or its relations to those muscular,
vascular, but more particularly nervous elements, which
constitute in their respective systems the arrangements cor-
responding to the haemal arch in the sclerotome, must have
been determined.
I must confess therefore my inability to discover the precise
view of the haemal arch taken by Professor Owen. Judging
from his diagram of the " ideal typical vertebra," and from his
general treatment of the subject, a chevron bone in the reptile
or mammal, or that portion of the cervical vertebra in certain
birds which completes the canal beneath the centrum, repre-
sents the primary typical form of this arch. It would also
appear to follow from his doctrine that the expanded form of
haemal arch, provided for the lodgment of the central organ of
circulation, and presented by the thoracic segments, is a
secondary formation the result of the removal of the primary
haemal arch from its "typical" position under the centrum,
and its intercalation between the elongated pleurapophyses.
But this doctrine appears to me to involve embryological con-
tradictions. The relations of these primary and secondary
forms of haemal arch in the neck and throat respectively are
not explained by it. The so-called haemal arch under the
cervical vertebra of the pelican is undoubtedly haemal in
function ; but as it excludes the oesophagus and trachea, it
cannot be the real or morphological haemal arch. In other
words, this so-called haemal arch cannot have been formed in
the " ventral folds " of the embryo neck.
Again, it is difficult to conceive how the pleurapophyses
and haemal arch of Professor Owen's " ideal typical vertebra "
can be developed together in the " ventral folds " of the embryo.
For, according to the doctrine of Professor Owen, a pleurapo-
physis may, in different instances, present two sets of relations.
In the thorax it is attached by opposite ends to adjoining
98 ON THE MORPHOLOGICAL CONSTITUTION OF
sclerous elements, and lies in the wall of the haemal chamber.
In the neck and tail it is connected to its own vertebra at one
end only, and does not lie in the wall of the haemal chamber.
The mode in which the continuously-arranged elements of the
costal arch of a bird the " pleurapophyses," " haemapophyses,"
and " haemal spine " are developed in the embryo is known.
But it is difficult to conceive how the detached and peculiarly-
arranged " pleurapophyses " and " haemal arch," as represented
in the " ideal typical vertebra," or exemplified in a proximal
caudal vertebra of a reptile or perenni-branchiate amphibian,
have assumed the positions they occupy, if they belong to the
same group of elements that is, if they all spring from or
originate in the wall of the visceral chamber.
Is the pleurapophysis a fundamental or primary element
of the haemal arch ? In other words, is it originally developed
in the wall of the visceral cavity, and in certain instances
afterwards extruded from it ? or is it merely a secondary ele-
ment in the haemal arch that is, formed externally to, or away
from it, and only intercalated into it in certain vertebrae ?
As a rib, so far as its development has been traced in the
series, appears to be formed in the inner layer of the " ventral
fold ;" and as it is previously connected or continuous with
the diapophyseal portion of the neurapophyses, its head and neck
being secondary formations, I am inclined to consider the caudal
transverse processes in the mammal, lizard, and amphibian as
lying in the position of the original " ventral folds," and that,
therefore, the feebly-developed " pleurapophyses " of this region
are the only representatives of its haemal arches, while the
chevron-bones have no title to this morphological distinction.*
* In dissecting lately a large crocodile, I found that an aponeurotic
membrane extended outwards and curved downwards on each side from the
extremities of the caudal transverse processes. These aponeuroses met one
another in the mesial line below the tail, and were there joined by a mesial
aponeurosis which extended down from between the chevron -bones. A layer
of fat one-third of an inch in thickness lay on the outside of the lateral apo-
THE SKELETON OF THE VERTEBRATE HEAD. 99
The processes which complete the canal under the posterior
cranial and anterior trunk centrums in certain fishes, and of
the cervical centrums in certain birds, are probably of the
same nature as the chevron-bones, which, according to Joh.
Miiller, appear to be developments of the inferior pair of con-
stituent pieces of the centrum.
We are entitled, then, to require that every part to which
the pleurapophyseal or haemapophyseal character is attributed,
should have been proved, by direct observation or otherwise,
to have been developed in the " ventral folds."
It appears to me very doubtful whether there are suffi-
cient grounds for limiting the number of morphological
elements in the haemal arch to one pair of " hsemapophyses "
and a "haemal spine ;" or to a pair of " pleurapophyses," a
pair of "hsemapophyses," and a "haemal spine;" while an
increase in the number of sclerous pieces is accounted for by
the principle of "vegetative repetition," or " teleologically."
While I admit the grouping of the elements of the more corn-
neuroses, and, embedded in it, the haemal divisions of the spinal nerves extended
outwards, downwards, and backwards, like a series of intercostal nerves. The
lateral muscular mass of the tail arranged in myotomes with metamyotomic
fibrous laminae, nearly as distinct as in the fish, lay on the outside of the layer
of fat. Each of the lateral aponeurotic cavities was occupied by the " femoro-
peroneo-coccygien " muscle of Cuvier, which arose from the under surfaces of
the transverse processes, the sides of the chevron bones and mesial aponeurosis,
and passed out of the cavity through a space left in its outer wall behind the
ischium to be inserted into the thigh-bone. The mesial membrane divided
above, its two laminae corresponding to the limbs of the chevron -bones, and
passing in front into the walls of the pelvis.
This arrangement appeared to me to indicate that the transverse processes,
the lateral aponeuroses, and the haemal divisions of the spinal nerves, were in
the position of the proper haemal arches of the tail ; that the two aponeurotic
chambers constituted in fact, together, the abdominal or visceral cavity,
divided by the mesial lamina, and occupied by a pair of muscles, referable to
that group of muscles which in the trunk lie on the inner surface of the vis-
ceral chamber, and that therefore the chevron-bones are not real haemal arches,
but subcentral developments.
100 ON THE MORPHOLOGICAL CONSTITUTION OF
plex haemal arches into an upper and a lower series, I am
compelled on philosophical grounds to deny that the sub-
division of a " pleurapophysis" or of a " haemapophysis," is
beyond the range of morphological law ; or that morphology
and teleology are distinct in the sense that the latter principle
provides for what the former is insufficient. Morphology and
teleology are merely opposite, because, in the present phase of
science, necessary anthropomorphic aspects of the same Divine
principle evinced in the laws of organisation.
Until, then, we know more than we do at present of the
laws which regulate the number of " centres of chondrification
and ossification," and until the constitution of the inferior
vertebral arches in the embryo and adult series has been more
fully analysed, I cannot give my assent to the expression for a
haemal arch involved in Professor Owen's osteological doctrine.
I must here allude to a point which does not appear to
have attracted that attention which it deserves. None of the
haemal arches of the head inclose the haemal axis. If we are
to consider the so-called median and lateral frontal with the
superior maxillary lobes as visceral laminae, then, as such,
they have no primordial relation with the haemal axis, which,
under the form of the cardiac-branchial tube, extends forward
as far only as the so-called " first visceral lamina." After the
haemal arches have been formed in " the first and other
visceral laminae," usually so called, of the head, the haemal
axis is found to be excluded from them. It is in consequence
of this remarkable developmental arrangement that the heart,
branchial artery, and its branches, in the fish and amphibia,
are situated below and external to the skeleton of the bran-
chial apparatus.
Before pointing out what appear to me to constitute cer-
tain of the developmental conditions on which this peculiar
relation of the haemal arches of the head to the haemal axis
is dependent, I must direct attention to another relation, in
THE SKELETON OF THE VEKTEBRATE HEAD. 101
which the cephalic haemal arches are peculiar. The hsemal
arches of the head are in immediate contact with the ali-
mentary tube ; they are lined by the mucous membrane,
which is also in contact with their centrums. There is, in
fact, no extension of the peritoneo-pleuropericardiac space into
the head. The cephalic portion of the primary abdominal
wall (Kopfseitenplatte of Kemak) becomes from the first
united to the corresponding portion of the cephalic primordial
vertebral system (Kopfurwirbelplatte) ; and the former, instead
of dividing into two layers one for the wall of the alimentary
tube, and another for the wall of the visceral cavity, with a
serous space between them as in the trunk becomes, in con-
junction with the latter, perforated by the branchial clefts.
The hsemal portion of the head, therefore, is distinguished
from the corresponding portion of the trunk, in presenting
metasomatomic clefts, in having no serous cavity, and in hav-
ing the haemal axis external to the hsemal arches of its sclero-
tomes. We are not yet in possession of sufficient data to
explain these various peculiarities of the head in the haema-
pod. I must direct attention, however, to the following facts,
which bear upon the cephalic exclusion of the haemal axis.
The anterior portion of the primordial alimentary tube, from
the cul-de-sac in which it terminates in front, back to its
vitellary margin, consists essentially of two parts ; a cephalic
portion, terminated by the cul-de-sac, is bounded laterally by
the " visceral laminae," from the so-called first pair of laminae
backwards, and becomes developed into the pharynx ; and a
cervico-thoraco-abdominal portion, bounded laterally by the
anterior portion of the primordial vertebral system of the
trunk and the corresponding portions of the primary ventral
wall. The primordial haemal axis (heart and branchial artery)
is formed within the pericardiac space, on the inferior aspect
of the posterior or trunk portion of the tube from which are
afterwards developed the oesophagus, stomach, duodenum, liver,
102 ON THE MORPHOLOGICAL CONSTITUTION OF
pancreas, and lungs. The heart and pericardium are at first
comparatively large, project downwards, and only pass back-
wards at a comparatively late period into the interior of the
hsemal arches of the thoracic sclerotomes in reptiles, birds,
and mammals. The cephalic portion, or pharyngeal cul-de-
sac, on the other hand, does not present originally any traces
of the development of the hsemome. This may be to a certain
extent explained by the great comparative development of the
cephalic portion of what would have been formerly considered
the " serous layer" of the blastoderm a. The extremities of
the so-called "first visceral laminse" have in fact approached
one another below, before the apex of the cardiac tube has
advanced so far forwards as to communicate with them. The
precise conditions, however, which determine the formation of
the sclerous elements of the mandibular, hyoidean, and bran-
chial arches on the inside of the corresponding vascular arches,
remain to be ascertained by future inquiry. At present I can
only conceive of these conditions as in some way dependent
upon the developmental relations to which I have alluded.
These relations of the haemal arches of the head must be
taken into consideration in determining the signification of the
branchial arches of the amphibian and fish. The division of
the sclerous system into dermo, neuro, and splanchno skeleton
was first systematically carried out by Cams. I was early
brought, by the study of the works of the philosophical and
ingenious Dresden anatomist, to adopt this threefold division
of the skeleton. I have latterly, however, been induced to
reject as untenable the doctrine of a splanchno-skeleton. I
believe it may be confidently asserted that no structure refer-
able in any way to the skeleton is developed in or around any
portion of the mucous layer of the vertebrate alimentary tube
beyond that part of it which belongs to the head ; in other
words, beyond the pharynx, or part perforated by the bran-
chial clefts. The mandibular, hyoidean, branchial, and pharyn-
THE SKELETON OF THE VERTEBRATE HEAD. 103
geal arches, the cartilages of the larynx, trachea, bronchial
tubes, and lungs, are all primarily developed in immediate
relation to the cephalic portion of the alimentary tube.
It is remarkable that those who refer the branchial and
pharyngeal arches to a splanehno-skeleton have not adduced
the external position of the haemal axis to these arches as an
argument in support of their opinion. On this ground, how-
ever, the hyoidean, and, I believe, the mandibular arch also,
as internal to the first, or to the first and second aortic arches,
would be also thrown into the system of the splanehno-skeleton.
Carus has accordingly done so in the case of the hyoidean
arch ; but Professor Owen, overlooking the fundamental em-
bryological relations which indissolubly connect all these
arches as serially homologous, holds the hyoidean to be a
" strong, bony, persistent arch of the true endo-skeleton ; "
while, on grounds which appear to me altogether secondary,
he refers the branchial and pharyngeal to the splanehno-
skeleton, and thus relieves himself of the onus of determining
their " homologies." From the view I have been led to take
of this subject, I am under the necessity of considering these
arches as true haemal arches, and as certainly referable to the
endo-skeleton as the mandibular arch itself. I also, for the
same reason, conceive that the complete morphology of the
skeleton of the head includes the homologies of the cartilages
of the larynx, trachea, and lungs.
The cartilages and bones developed in the actinal fibrous
laminse are most important elements in the sclerome. In the
head they are variously modified and arranged, not only for
the protection of organs, but also as a system of props to afford
additional security to the fundamental parts of the skeleton.
In the trunk they are chiefly subservient to the myome. They
thus exhibit their highest development in the framework of
the limbs, for the entire constitution of which they alone, I
believe, supply the elements.
104 ON THE MORPHOLOGICAL CONSTITUTION OF
The bony rays developed in the metamyotomic laminae of
fishes exhibit the most elementary forms of actinapophyses.
Here again I must differ from Professor Owen, who limits
the number of these " diverging appendages" to one- gene-
rally attached to the pleurapophysis on each side of the
vertebra. This " epipleural element" he considers to be a part
of the endo-skeleton, while the additional radiating bony fila-
ments he refers to the exo-skeleton, and recognises in them a
manifestation of the principle of "vegetative repetition."
While I admit that the so-called "epipleural spines" are the
most constant of these bones, yet, as the others are developed
in the same fibrous membrane, which has, moreover, no primary
relation to the dermal system, I cannot see on what grounds
they can be excluded from the endo-skeleton. As, again, I
cannot avail myself of the principle of " vegetative repetition"
in a morphological inquiry, and as I find all of these " addi-
tional ribs" connected with important modifications of the
myome, I account for their presence teleologically, and hold,
therefore, that they must also be explicable morphologically.
The question as to the typical number of actinapophyses
in a sclerotome cannot, it appears to me, be determined in the
present state of the science. Their existence and general
morphological relations having been ascertained, the conditions
which determine their position and number must remain for
future inquiry.
On these grounds I cannot, with Professor Owen, regard
the branchiostegal rays on each side collectively as a single
" diverging appendage." I not only recognise on each side of
the hyoidean arch of the osseous fish one series, but a double
series of actinapophyses. This double arrangement of the
branchiostegal rays has not, so far as I know, been recorded.
One series of these rays is attached along the outer, and
therefore morphologically anterior surface, and the other along
the inner, and therefore posterior surface of the cerato-hyal ;
THE SKELETON OF THE VERTEBRATE HEAD. 105
but as the two series are .attached, the one to the upper, the
other to the lower part of the bone, they form together a single
range for the support of the branchiostegal fold.
I recognise a similar but more developed form of this
double arrangement of actinapophyses in the variously-modi-
fied cartilaginous or semi-osseous double styles or plates which
are attached to the convexities of the branchial arches for the
support of the respiratory membrane of osseous fishes. These
branchial actinapophyses also exhibit that jointed or multi-
articulate structure so generally presented by the rays of the
mesial and bilateral fins.
This leads me to observe that I have not been able to
satisfy myself of the truth of the doctrine at present generally
held; that the inter-spinous bones and rays of the mesial fins
belong to the dermo-skeleton. I admit that, in certain in-
stances, these fins present more or less dermal bone in their
composition ; but I cannot see how fin-rays, from which the
skin and subcutaneous texture may be stripped, can be con-
sidered as portions of the dermo-skeleton. These rays can
scarcely, I conceive, be referred to the dermo-skeleton in the
cartilaginous fishes ; and as the rays of the bilateral fins re-
semble those of the mesial in their histological as well as in
their general relations, they ought to be placed in the same
category. The rays of the mesial, as well as of the bilateral
fins cannot, therefore, in my opinion, be consistently excluded
from that portion of the sclerome usually denominated neuro-
or endo-skeleton ; but like other elements of the endo-skeleton
which approach the dermal sclerous fibrous lamina, they may
coalesce with dermal bone.
I have been led to consider the inter-spinous bones and
mesial fin-rays as actinapophyseal elements. With reference
to the mesial position and characters of these bones, I would
remark, that it appears to me to be quite permissible, on mor-
phological grounds, to look upon each inter-spinous bone, with
106 ON THE MORPHOLOGICAL CONSTITUTION OF
its corresponding fin-ray, as consisting of a right and left
actinapophysis mesially united that is, to consider the right
and left halves of which they consist in the young fish as
fundamental elements of opposite sides of the body. This
view of the actinapophyseal character of the bones of the
mesial fins appears to be supported by the occurrence of double
anal and caudal fins in monstrous fishes, and also by the so-
called urohyal bone. The relations of this bone appear to me
to indicate that it is not referable to the basohyal elements of
the arch, but to the actinapophyseal. I recognise it as con-
sisting of two of these elements fused together at the mesial
plane.
I am further supported in the view which I take of the
actinapophyseal character of the inter-spinous bones and mesial
fin-rays, by the well-known and hitherto unexplained antero-
posterior duplicity which they exhibit in certain fishes. In
the Pleuronectidse, for instance, the inter-spinous bones are
attached in pairs, one bone in front and another behind each
spinous process. In these instances I conceive we have ex-
amples of mesial anterior and posterior actinapophyses in each
sclerotome. The corresponding fin-rays are, it is true, alternate,
but this does not affect the general principle, when we keep
in view the remarkable antero-posterior movements of certain
elements of the sclerome discovered by Eemak in the embryo,
and the highly-important observations of Professor Owen with
reference to the alternations of some of the elements of the
spine in certain reptiles and birds alternations undoubtedly
referable to movements of the kind discovered by Eemak.
In the head actinapophyseal elements are generally bar-
like, or more or less flattened from without inwards. From
the peculiar forms assumed by these elements in the head, an
anterior actinapophysis of one sclerotome may meet a posterior
one from the sclerotome in front, so as to form together a bar-
like or flattened bridge, or buttress, between the two. These
THE SKELETON OF THE VERTEBRATE HEAD. 107
bridge-like connections of neighbouring sclerotomes are not
unfrequently completed by the fibrous basis of the sclerome.
In birds, and the typical lacertians, indeed, in which the
actinapophyseal elements exhibit remarkable adaptations, the
fibrous matrix in which they are imbedded, and by which
they are connected, forms an essential feature of their arrange-
ment.
The actinapophyseal elements of a sclerotome are to be
distinguished as hsemal and neural those attached to the
haemal and those connected with the neural arches. The
hsemactinapophyses are the most usual and numerous, and
have hitherto been alone recognised as such by anatomists. I
shall therefore at present only remark, in reference to the
neuractinapophyses, that I consider as such the neural range
of " additional ribs," the interspinous bones and rays of the
dorsal fins, and of the neural half of the caudal fin in cartila-
ginous fishes, and also the inter-neural cartilages, to which
attention was first directed by Joh. Muller. In the cephalic
sclerotomes, the neuractinapophyses constitute the so-called
"sense capsules" and the system of " muco-dermal bones."
The so-called " muco-dermal bones" have been latterly referred
by the continental anatomists to the dermo-skeleton. I am,
nevertheless, inclined to believe, that when the general mor-
phological relations of these bones, and their existence in at
least reptiles and birds, are taken into consideration, they will
be admitted as elements of the endo-skeleton. They are not
the only bones in the head of the osseous fish which are tra-
versed by mucous tubes ; but from their superficial position
they generally are so, and from the same circumstance are
frequently overlaid by dermal bone. Professor Owen has
adopted the doctrine of the muco-dermal character of these
bones, and includes the lachrymal among them. Believing
the lachrymal to be a cephalic neuractinapophysis, I cannot
assent to the rejection of this bone from the endo-skeleton,
108 ON THE MORPHOLOGICAL CONSTITUTION OF
and more particularly to referring the perforation which gener-
ally characterises it to the system of dermal mucous canals.
The lachrymal canal is a metasomatomic opening. It is the
remaining portion of the cleft between the maxillary and
palatine visceral laminae The lachrymal bone is situated at
the upper end of this cleft, at the extremity of that metasoma-
tomic space in which the eyeball is situated viz. the orbit.
The lachrymal bone is therefore grooved or perforated by an
integumentary canal, which, as a portion of one of the original
clefts in the wall of the face, is retained in the adult as a pas-
sage for the secretion of the lachrymal gland.
The most important cephalic neuractinapophyses are those
fibrous, cartilaginous, or osseous structures which support and
protect the nose, eye, and ear. They exhibit their fundamen-
tal character most distinctly in the cyclostornatous and
plagiostomatous fishes, in which they consist of sessile or
pedunculated cartilaginous cups or capsules attached to the
outer margins of the cranium. In the other vertebrata these
<c sense-capsules," variously modified in form and texture, be-
come more or less involved in the wall of the cranium. In
their fundamental form they must be considered as parts of
the endo-skeleton, homologous in the hsemapod with those
parts of the dermo-skeleton of certain neuropods, such as the
crustacean, which carry the organs of sense, and are serially
homologous with its masticatory and ambulatory limbs.
Professor Owen refers the " sense-capsules" to the
splanchno-skeleton. But the organs of hearing, vision, and
smell, are developed not from or in connection with the
mucous layer of the blastoderma, but from the so-called
" serous layer" that is, from that superficial layer which pro-
duces the skin, its appendages, the cerebro-spinal axis, and the
primordial vertebral system. It appears to me that it would
have been more natural to refer the sense-capsules, as De
Blainville did, to the dermal system ; but their histological,
THE SKELETON OF THE VERTEBRATE HEAD. 109
embryological, and general relations, indicate, I believe, their
real nature as parts of the neuro-skeleton. .
The most complex and important development of the ac-
tinapophyseal elements of the sclerome are those arrange-
ments which constitute the framework of the limbs. As,
however, I find myself compelled to dissent from Professor
Owen's determination of the anterior pair of limbs as the
haemal arch and " divergent appendages" of the occipital ver-
tebra ; and as I also dissent from his general doctrine of
limbs, I shall reserve my observations on the subject for a
separate communication.
The osseous formations in connection with the subintegu-
mentary fibrous lamina constitute collectively the dermal por-
tion of the sclerome. As the constitution of the exo-skeleton
does not immediately bear on the object I have in view, I
shall merely observe, in reference to it, that a more extended
and systematic investigation of its structure and morphology
is at present very much to be desired.
From the statements already made, it will be observed
that I consider that the most general conception we can at
present reach of a vertebra or sclerotonie, is a somewhat ex-
panded or detailed form of Von Baer's ideal transverse section
of the vertebrate animal, which is based on the original
neural and haemal foldings of the blastoderma from the sides
of the corda dorsalis. With reference to the further develop-
ment of the idea, I venture to express my decided opinion,
that formally to announce the archetypal number of elements
in a segment of the skeleton is a premature attempt at gen-
eralisation, and that a dogmatic statement on a subject of this
kind must have a greater tendency to check legitimate induc-
tion the higher the authority from which it emanates..
The modifications which occur in the Sclerotomes towards or
at the front of the Head. It is generally admitted, that in
tracing backwards the series of sclerotomes in a vertebrate
110 ON THE MORPHOLOGICAL CONSTITUTION OF
animal, they become modified in form in proportion to the
withdrawal of the other organic systems, until at last the
sclerotome may become a mere nodule or filament. Although
it is also generally admitted that a certain amount of deteriora-
tion takes place in the sclerotome towards the anterior part of
the cranium, the nature and extent of the change has not
hitherto been precisely determined. I find that it presents,
according as the nasal fossae are, or are not present, two forms.
First general form of Deterioration. The deterioration is
much less in the first form than in the second. The first form
may be best observed in the mammal, in which alone the
nasal cavities are complete. The nasal fossae of the mammal
are bounded below by a series of at least four haemal arches,
the palatine, maxillary, intermaxillary, and ali-nasal, which,
along with the soft parts, form collectively the palatal vault
of the mouth, with the upper lip and under surface of the ex-
ternal nose ; these three continuous surfaces forming in fact
the anterior part of the sternal or haemal aspect of the head,
the palatal portion being inclosed within the mouth in con-
sequence of the elongation of the lower jaw. If now the
sclerotome, of which the intermaxillary bones constitute the
haemal arch, be examined, it will be found to present supe-
riorly the two nasal bones, as its neural elements ; but which,
instead of bounding, along with their corresponding centrum,
a neural space, assist the intermaxillary bones in forming two
spaces, which are completed, and at the same time separated
from one another by the centrum, which, no longer separating
a neural from a haemal space, separates a pair of lateral neuro-
haemal spaces, or nostrils, from one another. This modifica-
tion of the sclerotome depends, primarily, on its not being
required to enclose a segment of the neural axis ; and, second-
arily, on its co-operating in the formation of the nostrils.
This form of sclerotome, in which the centrum passes from
above downwards, I denominate catacentric, to distinguish it
THE SKELETON OF THE VERTEBRATE HEAD. Ill
from the ordinary form in which the centrum passes across,
which, therefore, I also occasionally find it convenient to in-
dicate as the diacentric form of sclerotome. The passage
from the diacentric to the catacentric form is exemplified in
the ethmoidal sclerotome, the haemal arch of which, consisting
of the pair of maxillary bones, enters into the formation of
the nasal passages. The centrum of this sclerotome has as-
sumed the form of a more or less compressed plate, which,
while it retains its lateral connection with the neurapophyses,
extends at the same time more or less upwards into the
neural space, and downwards between the nostrils, which,
under this sclerotome and the one behind, consist of a mesially
bisected haemal cavity.
The anterior terminal sclerotome in the non-proboscidian
mammals is cartilaginous and catacentric. Its neuro-haemal
chambers are closed in front by the junction of the anterior
margins of its neural and haemal elements. In consequence,
too, of the position of the external nostrils, which, as metaso-
matomic openings, are situated between the haemal elements
of this sclerotome and those of the sclerotome immediately
behind, its haemal elements are tilted forwards, so that towards
their junction with the neural elements their sternal margins
are continuous with the dorsal line of the nose. In the more
developed forms of this sclerotome, from one to three haemae-
tinapophyses on each side enter largely into its arrangements.
In the proboscidian mammals, instead of being greatly
developed, as might t naturally be expected, this sclerotome is,
on the contrary, much simplified. In the tapir the haema-
pophyses have disappeared, while in the elephant the neura-
pophyses alone exist in a comparatively undeveloped form.
I believe, however, that it will ultimately be admitted, that
the proboscis is not a mere elongation or development of the
external nose, like the pseudo-proboscis of the bear, racoon,
and coati, but a syssomatome.
112 ON THE MORPHOLOGICAL CONSTITUTION OF
Second general form of Deterioration of the Sclerotome at
the front of the Head. The character of this form of deteriora-
tion may be best observed in the intermaxillary or vomerine
sclerotome of the osseous fish. Instead of being reserved for
the purpose of forming portions of nostrils, the neural space
no longer required for the lodgment of a segment of the neural
axis disappears entirely, the neurapophyses being at the same
time generally absent. The centrum may also disappear, or
may exist in the form of a cartilaginous nodule ; a pair of
neurapophyses may therefore form the entire sclerotome.
These hsemapophyses generally extend outwards and down-
wards from one another, or from the centrum if it exists at
the mesial plane. They form together, therefore, an arch sus-
pended at its centre, with its piers unsupported. The hsema-
pophyses of the two sclerotomes immediately behind form re-
spectively two arches, the maxillary and palatal, suspended
by their centres from the base of the skull. The centres of
these two arches are, however, morphologically their approxi-
mated piers, the actual centres ; their sternal or haemal con-
junctions are not completed in the osseous fish, in conse-
quence of the non-formation of the nasal fossae. These three
incomplete haemal arches retain their embryonic form of im-
perfect visceral laminae. They do not bridge across to form
a palate, and therefore the first complete haemal arch in the
osseous fish is the mandibular. The palate in it is, therefore,
like that of the mammal, morphologically a portion of the ex-
ternal surface of the animal. But they differ from one another
in this respect, that the palate of the fish is a primary, that
of the mammal a secondary surface.
Number of Sclerotomes in the Vertebrate Head. It has
tended not a little to throw discredit on the vertebral theory
of the skull, that its advocates have differed much as to the
number of its constituent vertebrae. I am inclined to think
that these discordant views are the result of a tendency in
. THE SKELETON OF THE VERTEBRATE HEAD. 113
later inquirers to be influenced by that a priori, or " transcen-
dental " method, characteristic of those German and French
anatomists with whom the subject originated. For my own
part, so far from coinciding in the received opinion, that the
number of segments in the vertebrate head is the same in all
its forms, I believe that it varies. I shall state in the sequel
the grounds on which I hold the number of sclerotomes to vary
slightly in the heads of the ordinary forms of vertebrata. I
am, however, inclined to believe that there are indications
afforded by embryology and comparative anatomy, of the exist-
ence in certain forms of vertebrate head of a considerably greater
number of sclerotomes than has been generally supposed. I
base this conjecture, first, on the system of cartilaginous nasal
segments in the cyclostomes ; and, secondly, on the circum-
stance that if the head is to be distinguished embryologically
from the trunk, by the presence of " visceral laminae " separ-
ated by clefts, then not only the cyclostomes, but the still
more remarkable branchiostoma indicate a number of cephalic
segments, and a form of vertebrate structure, of which, in the
present state of the science, it can only be said that such a
form is deducible from the vertebrate type.
I recognise in the head of the fish, exclusive of the cyclo-
stomes, six sclerotomes ; in that of the amphibian and reptile
also six ; with the exception of the crocodiles, in which the
seventh is feebly developed ; in that of birds, six ; and in
that of mammals, exclusive of the proboscidians, seven.
I find it more convenient to examine these sclerotomes
from before backwards ; and I distinguish them provisionally
by the following designations :
1. EHINAL. 4. PRE-SPHENOIDAL.
2. VOMERINE. 5. POST-SPHENOIDAL.
3. ETHMOIDAL. 6. TEMPORAL.
7. OCCIPITAL.
i
114 UN THE MORPHOLOGICAL CONSTITUTION OF
Keeping out of view, therefore, the cyclostomatous fishes
and the proboscidian mammals, which present indications of
a greater number, the vertebrata generally possess all the
sclerotomes enumerated above, except the rhinal, which
exists only in mammals and crocodiles.
On a Fundamental Difference between the Cranium of the
Mammal and that of the Bird, Reptile, Amphibian, and
Osseous Fish. In my earlier attempts to unravel the intri-
cacies of this subject, I found myself opposed by difficulties
in passing from the mammalian to the lower form of cranium,
and vice versa. I afterwards discovered that this mainly de-
pended on the reciprocal development and atrophy of the
meta-neurapophyseal elements of four sclerotomes in the two
forms. In consequence of this, we had been hitherto con-
founding the frontal bone, or meta-neurapophysis of the eth-
moidal sclerotome of the mammal, with the so-called "proper
frontal bone," which is in fact the meta-neurapophysis of the
pre-sphenoidal sclerotome of the bird, reptile, amphibian, and
osseous fish, an element of which there are, and this only in
rare instances, faint or doubtful traces in the former; and
pari passu, we had been confounding the parietal bones, the
double meta-neurapophysis of the post-sphenoidal sclerotome
of the mammal, with the so-called parietals, the largely-de-
veloped meta-neurapophyses of the temporal sclerotome of
the bird, reptile, amphibian, and osseous fish, elements which
are much reduced in size, and masked in the former. Among
other important organic relations indicated in the existence
of these two forms of cranium, I would here more particularly
note their bearing on the encephalon. Of the two forms, that
of the fish, reptile, and bird, while it adheres to the common
type, is modified mainly in relation to the organs of smell,
sight, and hearing. That of the mammal, also adhering to
the common type, is modified in relation to the cerebrum
proper to that nervous structure superimposed upon the
THE SKELETON OF THE VERTEBRATE HEAD. 115
series of ganglionic masses at the base of the brain which are
serially homologous with the spinal cord.
EHINAL SCLEROTOME. In Mammals. The principal parts
of the cranium which remain unossified in the mammal are
the nasal septum and the cartilages of the nose. Of these, the
unossified portion of the nasal septum is the anterior prolon-
gation of the basal portion of the so-called " primordial
cranium." It is consequently a continuous mass of cartilage,
but is nevertheless referable to three sclerotomes ; its superior
portion completing the centrum of the ethmoidal ; its lower
portion the centrum of the vomerine ; and its anterior that
of the rhinal sclerotome.
The rhinal sclerotome in the mammal is fibrous, cartila-
ginous, and catacentric. Its centrum, formed by the anterior
portion of the nasal septum, extends from its neural to its
haemal margin. Its right and left neural elements are the so-
called superior or triangular cartilages of the nose. They
may be continuous with or merely attached to the neural edge
of their centrum. The anterior margins, or angles of these
cartilages, and the corresponding point of the septum or cen-
trum is the absolute anterior termination of the animal, or
more precisely of its morphological axis. The ridge of the
nose downwards and forwards to that point is neural or dorsal ;
beyond it, although continued in the same line, the ridge is
haemal or sternal.
The two alar cartilages are the haemapophyses of this
sclerotome. Variously modified in form, they are more or less
firmly attached to the lower margins of the upper cartilages.
In front they are attached to the septum, to which also they
are more loosely connected round the tip of the nose, being
frequently folded in on the ridges of the septum. In the
fibrous membrane occupying the sides of the space between
the posterior margins of the alar cartilages which together
constitute the haemal arch of their sclerotome, and the ante-
116 ON THE MORPHOLOGICAL CONSTITUTION OF
rior margins of the intermaxillary bones which form the hcemal
arch of the succeeding sclerotome, there are generally a number
of variously modified cartilaginous pieces. These pieces are
teleologically highly important elements of the rhinal sclero-
tome. Morphologically they are actinapophyses. When fully
developed, they are three on each side attached to the alar
cartilage. In the ox and other ruminants, the superior actina-
pophysis is an irregular lamina, which, imbedded in the fibrous
membrane, assists in supporting the wall of the nostril. The
second is a thick, short bar, articulated to the alar cartilage in
front, and jointed behind to the corresponding element of the
vomerine sclerotome, by which arrangement it is immediately
connected with the inferior turbinal bone, which is an actina-
pophyseal element of the ethmoidal sclerotome. The third or
inferior rhinal actinapophysis is a crutch-like cartilage, articu-
lated to the alar element by its stem, which is bent inwards,
then downwards, and outwards to the margin of the nostril,
which it supports by its curved transverse portion. In the
bear, racoon, and coati, the two superior actinapophyses are
much developed, and, along with the neurapophyseal, form
the cartilaginous wall of the trunk-like nose, or pseudo-
proboscis. In the phacochoer the acuminated nasal bones
curve down toward the intermaxillary, so as to separate the
neural elements of the rhinal sclerotome from one another.
The rhinal centrum is therefore much diminished in extent ;
but is, at the same time, strengthened for the support of the
nasal buckler by a deposit of bone. The haBmapophyseal and
actinapophyseal elements are thus pushed outwards, along
with the nostril, so as to produce that breadth for which the
snout of this pig is remarkable. In man the rhinal actinapo-
physes are reduced to the sesamoid cartilages. In the solipeds
they disappear altogether. The so-called semilunar cartilage
of the horse is, in fact, the alar cartilage itself, the internal
inferior angle of which, much elongated, supports the inner
THE SKELETON OF THE VERTEBRATE HEAD. 117
margin of the nostril, as the transverse limb of the crutch-like
inferior actinapophysis of the ruminant supports the outer
margin of the orifice.
TJie Rudimentary Rliinal Sclerotome in the Crocodiles. In
the crocodiles, as in the mammalia, the vomerine sclerotome
is traversed by the nasal fossae, which open therefore in front,
instead of behind it, as in the other reptiles and in birds. It
is evident therefore, that if the crocodiles do not possess, like
the mammalia, a rhinal sclerotome, their external nostrils
must present an exceptional arrangement ; for, instead of
being metasomatomic, they must be terminal. I find, how-
ever, that in the alligator the hoods which extend from the
anterior inner margins and septum of the osseous external
nostrils consist of dense fibrous tissue, covered by the muscles
which act upon them. This double fibro-muscular hood is so
arranged on each side as to have the oblique slit-like nostrils
situated between their outer margins and the intermaxillary
edges. If a plate of cartilage were developed in the margin
of each hood, the whole arrangement would occupy the posi-
tion and exhibit the relations of an ali-nasal cartilage a
rhinal hsemapophysis, or neurapophysis, as in the elephant.
VOMERINE SCLEROTOME. In Mammals. In the mammal
the vomerine is a perfect catacentric sclerotome. The nasal
bones are its neural elements, as they occasionally run together,
and are evidently, as has been generally admitted, serially
homologous with the frontals and parietals ; they must be
viewed as metaneurapophyses, the neurapophyses being absent
in the absence of a nervous centre. The intermaxillaries meet-
ing below form the haemal arch, and the centrum consists of
the vomer, with a corresponding portion of the cartilaginous
nasal septum.
The vomer is a bone peculiarly mammalian. It may be
said to make its appearance as a developed element, along
with the completed nasal fossae. But its development in the
118 ON THE MORPHOLOGICAL CONSTITUTION OF
mammalian series is not only dependent on the nasal fossae,
but on the intermaxillaries, with which, as will be shown in
the sequel, it is invariably connected. Its passage backwards
under the centrum of the ethmoidal sclerotome to abut against
that of the pre-sphenoidal, is, as will also appear, a mamma-
lian peculiarity, and an instance of that antero-posterior elon-
gation and of that overlapping arrangement so frequent in the
adaptation of the cephalic centrums to one another.
When the inferior turbinal bone, an actinapophysis of the
ethmoidal sclerotome, is highly developed, as in the ruminants,
a strong flattened bar of fibro-cartilage is attached to the
inner aspect of the ascending process of the intermaxillary,
and widening out into a soft curved cartilaginous plate, com-
pletes the fore part of the inferior turbinal, connecting it at
the same time to the second actinapophysis or turbinal pro-
cess of the ali-nasal cartilage. I look upon this appendage as
a ha3mactinapophysis of the vomerine sclerotome ; and serially
homologous with the second or turbinal hsemactinapophysis of
the rhinal, and with the turbinal hsemactinapophysis of the
ethmoidal sclerotomes. These hsemactinapophyses have all
of them been enclosed within the nasal chamber during de-
velopment ; having passed in through the metasclerotomic
clefts, instead of forming parts of the nasal wall, or projecting
from its outer aspect.
Vomerine Sclerotome in the Crocodiles. It is remarkable
that the familiar fact of the peculiar position of the external
nostrils of the crocodiles should not hitherto have attracted
attention. They open in front of the intermaxillaries as in
the mammals ; whereas, in the typical lacertians, and in the
extinct plesiosaurs, ichthyosaurs, and pterodactyles, in the
ophidians, amphibians, and birds, they open behind these
bones. On this peculiarity in the crocodiles depends the very
perfect development of the anterior part of the nasal septum.
Along with the complete and pervious intermaxillary arch, we
THE SKELETON OF THE VERTEBRATE HEAD. 119
find a complete although cartilaginous vomer. Of that part
of the extended nasal septum of the crocodiles, corresponding
to the mammalian nasal septum, the only ossified portion is
an elongated single or double slip along the lower edge of its
ethmoidal region, and continuous with the elongated pre-
sphenoidal centrum. Professor Owen considers this slip of
bone as the vomer. I will only observe at present that, hold-
ing the vomer to be invariably in relation to the intermaxil-
laries, I can only conceive, as the vomer in the crocodile, that
elongated cartilaginous portion of the nasal septum which
extends beneath the elongated nasal bones to the intermaxil-
lary suture.
Vomerine Sclerotome in Typical Lacertians. In the proper
lizards this sclerotome is imperforate. The intermaxillaries
not only close in at the palate, but in front also ; the more or
less elongated and combined ascending processes joining the
united or distinct nasal bones. The centrum is represented
by the anterior part of the cartilaginous septum. The two
bones, usually described as the double vomer of the lizard,
belong, as I shall endeavour to show in the sequel, to the suc-
ceeding sclerotome the ethmoidal.
Vomerine Sclerotome in Birds. The yomerine sclerotome
of the bird consists principally of the intermaxillaries, but
partly of the persistent anterior portion of the primordial
cranium. The intermaxillaries speedily unite below and in
front, so as to form the first and principal part of the
beak. Their united ascending processes extend up to the
so-called " principal frontal bone," and separate completely
the so-called nasal bones. In the sequel the evidence will be
adduced on which I found my belief that the bone called in
birds the "frontal," or "principal frontal," is not the frontal
of the mammal ; but that the two so-called nasal bones in the
bird are the two halves of that bone which in the mammals
is called frontal. If so, where are the nasal bones of the bird ?
120 ON THE MORPHOLOGICAL CONSTITUTION OF
as the ascending processes of their intermaxillaries, which
occupy the proper position of the nasals, have not been ob-
served as separate centres of ossification ; and as the greater
number of chelonian reptiles want these bones, and resemble
birds in the general character and horny covering of their
beaks, I am inclined to believe that the nasal bones are defi-
cient as ossified elements in the bird. In young birds, aiter
boiling or maceration, the osseous elements of the beak may
be removed, and the anterior part of the primordial cranium
brought into view. In the fore part of its septum we again
recognise the vomerine centrum, but more or less deficient in
certain birds from the septal perforation peculiar to them.
The upper margin of the cartilaginous septum, where it is in
contact with the ascending processes of the intermaxillaries,
flattens out into a lamina, which partly roofs over the external
nostril on each side. These marginal processes of the cartila-
ginous vomerine centrum extend down in front, so as to line
the fore and under part of the nasal fossse, projecting some-
what behind the intermaxillary margin of the external nostril.
The broad projecting upper portion of the cartilaginous septum
occupies the position of the nasal bones, while the inferior
portions project from behind the interrnaxillaries, like oper-
cular actinapophyses. In the chick the part of the primor-
dial cranium just described as belonging to the vomerine
sclerotome presents an opaque aspect and fibro-cartilaginous
structure, contrasting with the hyaline cartilage posterior to
it a peculiarity pointed out by Eeichert as characteristic of
certain portions of the primordial cranium. It will be ob-
served that I do not consider the bone or bones usually called
" vomer" in the bird as correctly designated. In the sequel
I shall indicate the grounds on which I hold these bones to
be the upper elements of the palatine arch.
The Vomerine Sclerotome in Chelonian Reptiles. The inter-
maxillaries in the chelonian, united below, complete the front
THE SKELETON OF THE VERTEBRATE HEAD. 121
of the palate, alveolar margin, and floor of the nasal fossae.
The only trace of ascending processes which they present is a
compressed spine, which projects upwards at their junction in
the median line of the nasal opening of the cranium. The
lateral margins of that opening are formed by the maxillaries
alone ; its upper margin by the so-called pre-frontals, except
in Hydromedusa and certain fossil forms. The cartilaginous
septum of the nasal fossae extends up from the intermaxillary
suture to that of the pre-frontals.
Is the chelonian vomerine sclerotome modelled on that of
the crocodile, or of the bird ? The chelonian presents the first
stage in the remarkable development of the nasal passages
exhibited by the crocodiles. But the general deficiency of the
nasal bones, the indications of ascending processes of the
intermaxillaries in the mesial plane, the formation of the
posterior margins of the external nostrils by the maxillaries,
appear to me to show that in the construction of its vomerine
sclerotome, the chelonian differs from the crocodiles, and
resembles the typical lacertians, the ophidians, amphibians,
and the birds. The cartilaginous lining of its nasal fossae, a
remnant of its primordial cranium, projects, in general, a little
beyond the margins of the osseous nostrils, as in birds ; but
in Trionyx and Chelys, the projecting margins run forward
together in the form of a double cartilaginous proboscis.
TJie Vomerine Sclerotome in the Osseous Fishes. I have
already described the general constitution of the vomerine
sclerotome of the osseous fish, as one form of deterioration of
the fore part of the cranium. Its centrum, the vomer, when it
is present, is merely a cartilaginous nodule in the longitu-
dinal axis of the basis of the cranium, in front of the bone
usually described as the " vomer," but which I believe to be
the centrum of the ethmoidal sclerotome ; the neural elements
are those scale-like bones, which Cuvier recognises, I believe
correctly, as the nasals. Professor Owen considers these
122 ON THE MORPHOLOGICAL CONSTITUTION OF
bones to be the turbinal divisions of the olfactory " sense-
capsules ;" and, according to his doctrine of the sense-capsules,
elements of the splanchno-skeleton. If Professor Owen under-
stands by the turbinal divisions of the olfactory sense-cap-
sules, bones homologous with the inferior turbinated, or even
the so-called ethmoidal turbinated bones of the mammal, it is
difficult to understand, on embryological principles, how, as
splanchnic bones, and as developed in connection with the
maxillaries, they come to be situated under the integument of
the upper surface of the head. It is, moreover, questionable,
whether the sclerous capsule of this, or of any of the special
sense-organs, is ever divided, and its parts separated from one
another, under such relations as those presented by the so-
called " turbinals" and " ethmoidal" of the osseous fish.
The intermaxillaries form the principal and more peculiar
elements of this form of vomerine sclerotome. The nasal
fossae being entirely absent, the merely fibrous olfactory sense-
capsule is subcutaneous, or partly under cover of the nasal
bones (turbinals) ; the vomer is not developed as a septum,
but merely to supply a fulcrum for the intermaxillaries, which
may even constitute the entire sclerotome, but are never
united below, so as to form a complete hsemal arch.
THE ETHMOIDAL SCLEROTOME. The ethmoidal sclerotome,
and the presphenoidal immediately behind it, present, in the
different forms of vertebrata, various remarkable modifications
of their elements, partly dependent on the position of the
olfactory lobes of the brain, partly on the position of the
olfactory capsules themselves, partly on peculiar adjustments
of the nasal fossae, and on the arrangements subservient to
mastication.
The withdrawal from behind forwards of the neural axis,
in the course of development, from the posterior extremity of
the neural canal, is accompanied by well-known changes in
the evacuated but rapidly-increasing posterior trunk sclero-
THE SKELETON OF THE VERTEBRATE HEAD. 123
tomes. Corresponding, but much more remarkable changes,
to which attention has not been hitherto sufficiently directed,
accompany the withdrawal from before backwards of the
anterior part of the brain from the ethmoidal and pre-
sphenoidal sclerotomes. The neural portions of these sclero-
tomes assume more or less of the catacentric character they
become demicatacentric. The neural chamber of the ethmoidal
sclerotome of the mammal, in addition to a portion of the
cerebrum proper, lodges its homologous segment of the
neural axis. In the bird the neural chamber of this sclero-
tome is completely evacuated by the neural axis, which not
only leaves it, but withdraws in part also from the pre-
sphenoidal. The absence of the anterior extremity of the
neural axis from' the neural chamber of the ethmoidal
sclerotome is accompanied by the division of that chamber
into a right and left compartment by a mesially laminar
centrum, the two compartments being occupied by the olfactory
capsules. The olfactory lobes in the bird are not only with-
drawn from the ethmoidal sclerotome, but retreat to a certain
distance backwards in the neural chamber of the presphenoidal.
To this extent the chamber becomes catacentric ; but instead
of its two resulting compartments being occupied by new
structures, having only to transmit the olfactory nerves, their
outer walls collapse upon the mesially laminar centrum, and
very generally disappear almost altogether, so as to leave the
nerves uncovered on the sides of the laminar centrum as they
pass forward to the ethmoidal chambers. The neural chamber
of the ethmoidal sclerotome of the bird, containing only the
olfactory capsules, is so connected with the bones of the face
and with the neural arch and centrum of the presphenoidal,
as to be more or less movable along with the lower mandible.
The ethmoidal in the mammal is thus seen to be the anterior
cerebral sclerotome, while in the bird it becomes the posterior
facial sclerotome.
124 ON THE MORPHOLOGICAL CONSTITUTION OF
In the reptile both the ethmoidal and presphenoidal (?)*
sclerotomes are evacuated by the neural axis, the olfactory
nerves alone passing along in the compressed tubular, partially-
catacentric neural chamber of the latter the olfactory capsules
occupying the right and left chambers of the former. In
reptiles, however, the very varied forms assumed by the bones
of the face, and more particularly by those of the palatine
arch, in relation to the nostrils, and the arrangements for
mastication, produce numerous remarkable modifications of
these two sclerotomes.
In passing from the reptile to the fish, the ethmoidal
sclerotome may be said to gather together its scattered elements,
and to present a centrum and neural arch frequently as com-
pact as the human, but modified by the deficiency of nostrils,
and by the withdrawal of the neural axis.
Ethmoidal Centrum and Neural Arch in the Mammal.
The human cranium, as the most perfect in the higher of the
two forms of skull, will not unfrequently be found to afford a
clue to the signification of bones which, being only applied to
their final purposes in it, are more or less masked in the other
mammalia, and apt to be misunderstood altogether in the fish,
reptile, and bird. If we examine in connection the two bony
masses, which, in the current nomenclature of human anatomy,
are distinguished as frontal and ethmoid, they will be seen to
constitute a ring, the space within which is greatly dilated
behind, in consequence of the vast expansion, more particularly
of the upper and lateral portions of the frontal, while it is
diminished to a tubular chink in front, and is so indistinct
towards the nasal fossae that the older anatomists named it
" foramen caecum." (?) The development of this bony ring
shows it to consist of five pieces. These are the mesial plate,
including the crista-galli of the ethmoid, the lateral masses of
* This and the succeeding marks of interrogation we have found in a copy
annotated by the author. EDS.
THE SKELETON OF THE VERTEBRATE HEAD. 125
the same bone, including the corresponding halves of the
cribriform lamina, and the two halves of the frontal. We
have here, therefore, a centrum, a pair of neurapophyses, and
a divided metaneurapophysis. The pair of olfactory nervous
centres, which terminate in front the entire series of segments
of the neural axis, are the segments of that axis, homologous
with this neural arch and centrum. In the mammalia only
is the upper part of this neural arch expanded and adapted
for the protection of the more or less developed fore part of
the cerebrum proper. In the central portion and lateral masses
of the ethmoid, and in the frontal bones of the mammal, I
recognise the centrum and neural arch of a sclerotome, which
I provisionally distinguish as the ethmoidal.
Centrum and Neural Arch of the Ethmoidal Sclerotome in
the Osseous Fish. The more or less concurrent statements of
Oken, Bojanus, Geoffroy, Cuvier, and Owen, as well as the
relations of the bones themselves, leave no doubt as to the
homology of the so-called pre-frontals of the fish. They are
neurapophyseal elements, the lateral ethmoidal masses of the
mammal in another form, and minus the ossified olfactory
capsules. The median bone superimposed upon the "pre-
frontals " of the fish, and which has been very generally held
to be the united nasals, and the spine of the olfactory vertebra,
must be homologous with the frontal bone of the mammal if
its relations to the " pre-frontals " and olfactory nerves of the
former are compared with those of the ethmoid and frontal
bones, and the olfactory nerves of the latter. Professor Owen,
while he adopts the determination of the superior median
bone as the united nasals, also holds by the hitherto unanimous
opinion of anatomists, that the median bone armed with teeth,
situated below the pre-frontals of the fish, is the vomer.
Guided by the ethmoid of the mammal, I cannot see in this
bone aught else than the homologue of the central element of
the mammalian ethmoid. The vomer is a mammalian bone ;
126 ON THE MORPHOLOGICAL CONSTITUTION OF
if it appears in the fish at all, it is a cartilaginous or semiossi-
fied nodule between the intermaxillaries. That the centrum
of the ethmoidal sclerotome in the fish, considered as the
homologue of the central plate or bar of the mammalian
ethmoid, should carry teeth in the fish, is not more remarkable
than that one of the centrums of the cervical vertebras in that
class of animals should be so armed.
Hcemal Arch of the Ethmoidal Sclerotome in the Mammal
and Osseous Fish. I have commenced my account of the
morphological constitution of this important sclerotome by
pointing out the typical arrangement which its neural arch
and centrum present in the mammal and fish. As the arrange-
ment of these parts of this sclerotome becomes much and
variously modified in birds, reptiles, and amphibia, in relation
to the various forms presented by the organs of smell and the
nostrils, it will be necessary, before proceeding further, to
examine the constitution of its haemal arch. Even in its most
complex form, this haemal arch, like those of the rhinal and
vomerine sclerotomes, consists of two elements only, the right
and left maxillary bones. In the osseous fish they resemble
the " lateral frontal processes " in the embryo ; they form only
an incipient arch like that formed by the vomerine haemapo-
physes in front of them. They do not invariably carry teeth.
They are variously connected to the haemapophyses before
and behind them, and superiorly to the lateral and fore part of
the centrum, neurapophyses, and metaneurapophyses of the
neural arch of their own sclerotome.
The maxillaries of the mammal, more or less extended
from before backwards, and increased in breadth and depth to
adapt them to their functions in mastication ; meeting .one
another below, to form a great part of the vault of the palate,
and to assist in the formation of the nasal passages ; hollowed
out to combine lightness with strength ; and buttressed by
numerous connections with neighbouring bones, nevertheless
THE SKELETON OF THE VERTEBRATE HEAD. 127
retain their connection with the neural portion of their own
sclerotome, being attached superiorly to the lateral masses of
the ethmoid, and to the frontal. They are not articulated, as
in the fish, to their centrum ; but those connections to the
neurapophyses and metaneurapophyses, which in fish are
affected by ligaments, are sutures in the mammal. In the
sequel it will be shown, that of the two connections of the
maxillary that to the frontal, and that to the lateral ethmoid
the former is the most constant ; presenting in my opinion
the fundamental discriminative character of the remarkably
modified frontal of the bird, reptile, and amphibian.
The Ethmoidal Sclerotome in the Bird. The ethmoidal
sclerotome is remarkably modified in the bird. It forms no
part of the cranium proper, but assumes the position and
structure of a facial sclerotome. The bird, like the mammal,
has two proper facial sclerotomes. In the former there are
the vomerine and the ethmoidal ; in the latter the rhinal and
vomerine. In the majority of birds, also, the ethmoidal
sclerotome, along with the vomerine, moves more or less freely
on the presphenoidal. It is, moreover, peculiar in being
chiefly devoted to the economy of the organs of smell ; in
having its metaneurapophyseal elements separated from one
another by the passage backwards of the conjoined ascending
processes of the intermaxillaries ; in the feeble development
of its hasmapophyses ; and in its cavities being altogether
neural, its neurapophyseal elements forming more or less of
its palatal aspect.
The metaneurapophyses of the ethmoidal sclerotome of
the bird are the so-called nasal bones. From their invariable
connections with the maxillaries, I cannot see in these " nasal
bones " aught else than the proper frontal bones the frontals
of the mammal. They are separated from one another by the
ascending processes of the intermaxillaries ; a circumstance
which does not militate against their being the right and left
128 ON THE MORPHOLOGICAL CONSTITUTION OF
halves of a metaneurapophysis. They are more or less
elongated in the antero-posterior direction ; and they bound
the posterior margins of the external nostrils by the descend-
ing processes which connect them with their maxillaries. To
distinguish them from the metaneurapopjiyses of the pre-
sphenoidal sclerotome, I designate them ethmoido-frontals.
The arrangement of the centrum and neurapophyses of
this sclerotome in the bird appears to me to have been in a
great measure overlooked, from having been examined in the
macerated skull, in which these parts, as consisting principally
of cartilage, are to a great extent absent.
The centrum consists of the posterior and greater part of
the mesial cartilaginous lamina, the interior portion of which
forms the vomerine centrum. The ethmoidal portion of this
laminar mesial cartilage flattens out at its upper margin, in
the same manner as the vomerine portion in front ; and like
the flattened upper edge of the so-called " ethmoid bone "-
the centrum of the presphenoidal sclerotome behind. In the
same manner as the flattened upper margin of the vomerine
portion extends outwards on each side, so as to form a hood
over the upper and fore part of the external nostrils, the
flattened upper margin of the ethmoidal portion of the septum
passes outwards on each side, under cover of the ascending
processes of the intermaxillary, and under the ethmoido-
frontal, extending down more or less to the level of the
palatal plate of the maxillary, and then turning in towards
the mesial plane, approaches or meets the lower margin of the
mesial lamina itself. Posteriorly, these curved cartilaginous
plates close in upon the posterior margin of the septum ;
which is not continuous with the anterior margin of the
laminar septum of the presphenoid. They are each, however,
perforated or notched for the transmission of the olfactory
nerve ; and they also leave on each side of the septum at
their posterior inferior angles, a space for the posterior nasal
THE SKELETON OF THE VERTEBRATE HEAD. 129
orifice. The superior and middle turbinated folds of the
nasal chamber on each side are also supported by turbinated
cartilaginous projections from the internal surfaces of their
plates.
I have already stated that the anterior fibre-cartilaginous
portion of the persistent part of the primordial cranium of the
bird enters into the structure of its vomerine sclerotome ; it
will now be observed that its posterior hyaline portion enters
into the formation of the ethmoidal sclerotome. In the
majority of birds the septal lamina continues cartilaginous, as
well as the greater part of the curved lateral plates, with
their internal turbinal projections. A more or less extended
portion only of each curved plate becomes ossified when it
extends inwards across the palate ; and the ossified portion
becomes anchylosed to the maxillary, or to the descending
maxillary process of the ethmoido-frontal (" nasal "), and in
many birds to the anterior extremity of the palate bone.
I recognise, therefore, the posterior part of the nasal septum
as the centrum ; the so-called " nasals " as the meta-neurapo-
physes ; and the more or less ossified lateral and inferior walls
of the olfactory chambers as the neurapophyses of the eth-
rnoidal sclerotome of the bird. If it be objected to this
determination, that the parts which I consider as neurapo-
physes are only portions of the olfactory sense-capsules, I
would merely observe that these sense-capsules are in fact
combined with the neurapophyseal portions of the ethmoidal
sclerotome in the bird, as in the primordial cranium of the
mammal, reptile, and amphibian, and as in cartilaginous
fishes ; but that this circumstance in no way nullifies the
existence of the neurapophyseal element itself, either in the
sclerotome with which the olfactory capsules, or in those with
which the ocular and auditory capsules, are connected. I
would also observe that I base my determination of the
neurapophyseal character of these parts, not merely on their
K
130 ON THE MORPHOLOGICAL CONSTITUTION OF
relations in the bird, but on the varied relations exhibited by
their corresponding parts in reptiles.
The maxillaries or hsemapophyses of the ethmoidal sclero-
tome are feebly developed in the bird. Connected above,
chiefly to the descending processes of the ethmoido-frontals,
and more or less prolonged in the antero-posterior direction,
the maxillaries do not invariably complete the haemal arch.
Their region, therefore, of the palate, is more or less completely
occupied by the neurapophyseal plates of their own sclerotome.
The Etlimoidal Sclerotome in the Chelonian. The connec-
tion of the maxillaries of the tortoises and turtles, by means
of the ascending processes of these bones, with the so-called
pre-frontals, appears to me to indicate that the latter are
homologous with the ethmoido-frontals of the bird, or the
frontals of Mammalia. I recognise in them the meta-neura-
pophyses of the ethmoidal sclerotome. Each of these bones
sends down from its posterior margin a lamina, concave in
front, and forming, with the concave under surface of the bone
itself, the posterior superior hollow of the nasal fossa. The
inner margins of these two descending laminae give attachment
to the anterior margins of the fibre-cartilaginous laminae,
which bound laterally the compressed pre-sphenoidal neural
space, and form the so-called interorbital septum. The inner
margins of the two descending frontal laminae are, therefore,
separated from one another above by the breadth of the fore
part of the groove on the mesial part of the under surface of
the combined so-called "frontals." If now the macerated
skull of the turtle be examined, it will be found that a
complex bony piece, the so-called "vomer," connects by its
pair of short divergent upper processes the inferior extremities
of the inner margins of the descending frontal processes, con-
verting the space between them into a triangular orifice. This
so-called vomer, after sending a horizontal plate backwards
between the palatines to form the mesial portion of the
THE SKELETON OF THE VERTEBRATE HEAD. 131
common orbital floor, and to support the cartilaginous bar-like
centrum of the pre-sphenoid, passes down as the osseous septum
of the posterior nares, and terminates in the form of a penta-
gonal plate in the palate, between the palatines and maxillaries,
and in some species in a hexagonal form, between the palatines,
the maxillaries, and intermaxillaries. The relations of the
ethmoidal neurapophyses to their meta-neurapophyses in the
bird, and the presence of the former in the maxillary
region of the palate, led me to suspect that the so-called
" vomer " of the turtle is the combined neurapophyses of its
ethmoidal sclerotome. But its posterior horizontal laminar
process which supports the cartilaginous pre-sphenoidal cen-
trum, as well as the process which forms the septum of the
posterior nares, indicated the probability of the " vomer " being
a still more complex bone. I have not met with the palatal
plate as a separate bone in the turtle, although in longitudinal
sections I have observed faint indications of its having been
so. I find, however, that in certain tortoises, not only is the
palatal plate connected by a distinct suture to the upper
portion of the so-called " vomer," but it is divided by a similar
suture in the mesial line of the palate into two halves. In
these tortoises, therefore, the separation of the posterior nares,
the junction of the descending processes of the ethmoido-
frontals, and the support of the cartilaginous bar-like centrum
of the pre-sphenoid, are affected by a distinct bone, which,
including its connections to the palatines, presents all the
characters of the so-called " vorner " of the bird. But I have
already stated my belief that the bone so-called is not the
vomer of the bird ; and in the sequel I shall state the grounds
on which I hold it to be the combined ento-pterygoids the
upper elements of the palatine arch.
JEthmoidal Sclerotome in the Crocodiles. In the crocodiles
proper, and the gavials, the lachrymal is interposed between
the so-called pre-frontal and the maxillary. In the alligators
132 ON THE MOKPHOLOGICAL CONSTITUTION OF
the maxillary resumes its connection with the pre-frontal,
which it had lost in the two other families on account of the
elongation of the snout. The pre-frontals in all the crocodilians
are separated from one another mesially by the passage back-
wards of narrow contiguous processes of the nasals, and by
similar processes which pass forwards from the so-called
"proper frontals" in this respect resembling the so-called
" nasals " of the bird, which are separated from one another
by the ascending processes of the intermaxillaries.
Assuming the relations of the pre-frontals of the croco-
dilian to the maxillarj- arch as evidence of their being the
meta-neurapophyses of the ethinoidal sclerotome that is,
collectively, the homologue of the mammalian frontal the
next elements of this sclerotome to be determined are its
neurapophyses. At this point the type of ethmoidal sclero-
tome exhibited by the bird, and the modification of that type
presented by the chelonian, indicate its character in the
crocodilian. The descending processes of the pre-frontals of
the crocodiles are connected inferiorly to the ascending pro-
cesses of the so-called " palate-bones." Now, a bone connected
to the homologue of the mammalian frontal cannot well be
considered as the palate-bone, even although it be situated
between and united by suture to the maxillary and pterygoid.
But a bone with such relations, if viewed in the light of the
corresponding relations of the ethmoidal neurapophyses of the
bird, indicates its own real nature. The ethmoidal neura-
pophyses of the bird, connected above with the ethmoido-
frontals, form below more or less of the palatine vault. The
ethmoidal neurapophyses of the chelonians, pushed away
forwards and downwards from the ethmoido-frontal by the
ento-pterygoid, still form a part of the vault of the palate. (?)
In like manner I recognise, in the so-called " palate-bones "
of the crocodilian, the neurapophyses of its ethmoidal sclero-
tome. The ethmoido-frontals and neurapophyses of the bird,
THE SKELETON OF THE VERTEBRATE HEAD. 133
form, along with their cartilaginous septum or centrum, a
complete catacentric neural ring. The interposition of the
ento-pterygoid of the chelonian separates the meta-neura-
pophyses from the neurapophyses of the ethmoidal sclerotome,
and at the same time separates the neural space into an upper
portion, mesially divided by the cartilaginous septum or
centrum for the passage of the olfactory nerves, and into an
inferior, mesially divided by the ento-pterygoid itself for the
right and left nasal passages. A similar but somewhat
modified change is effected in the ethmoidal sclerotome of the
crocodilian, by the interposition of the anterior extremities of
its pterygoids which anterior processes I believe to be, in
fact, the ento-pterygoids. These anterior, generally mesially
united, processes of the pterygoids of the crocodilian, were
considered by Cuvier as representing the under portion of the
mammalian vomer. He describes them as two osseous pieces
fixed to the inner margins of the " palate-bones," in front of
the "anterior frontals," and of that part of the pterygoid
which covers the nasal canals. Professor Owen describes
these pieces as the lt vomer,' 7 and as being generally anchylosed
to the fore part of the basi-sphenoid ; but he adds the follow-
ing very important observation, which I have verified, that
they (the " vomer ") form a distinct bone in a species of alli-
gator, which passes so far forward and downwards as to
appear in the form of a plate in the vault of the palate, in
front of the palate-bones.
That this double bony splint is not a vomer, as Cuvier
supposed, must be evident, if the vomer is to be considered as
an element of the vomerine sclerotome. It cannot be, as
Professor Owen states, a vomer united to the " basi-sphenoid ;"
because, in front of the elevated, laterally compressed, quad-
rilateral process which passes forwards and upwards from the
centrum of the post-sphenoid, the real axis of the skull is
continued forward in the form of a compressed cartilaginous
134 ON THE MORPHOLOGICAL CONSTITUTION OF
bar, which is the centrum of the pre-sphenoid, and which
passes in front into the cartilaginous nasal septum, which
constitutes the ethmoidal and vomerine centrums. The
crocodilian and chelonian skulls are, in fact, entirely destitute
of ossified central elements in front of their post-sphenoidal
centrums, the superincumbent framework in these forms of
cranium being supported along the base, not by ossified cen-
trums, but by greatly expanded and modified pterygoids,
ento-pterygoids, ethmoidal neurapophyses, maxillaries, and
inter-maxillaries, immediately above which series of bones
lies the persistent central axis of the primordial cranium, as
far back as the ossified centrum of the post-sphenoidal sclero-
toine. In the mesial antero-posterior section of the macerated
skull of the Crocodilus vulgaris, a suture will be found com-
mencing in front of the common orifice of the Eustachian
tubes, and terminating at the lower part of the root of the
laterally-compressed post-sphenoidal process already alluded
to. In front of this suture, the' section presents no traces of
central elements, the pterygoids and so-called "palatals"
taking their places. In a section of this kind in the Museum
of the University of Edinburgh, the extremity of the anterior
process of the pterygoid passes forwards and downwards,
appearing in the suture between the two "palatines," about
an inch from their anterior margins ; the right and left por-
tions exposed on the vault of the palate being separated from
the " palatines " by surrounding suture, and forming together
a narrow double surface, one-eighth of an inch in length. In
the section to which I allude, and in similar sections, I ob-
serve traces of the line of anchylosis between these anterior
processes and the pterygoids themselves. These lines run up-
wards and forwards, and appear to include the anterior and
greater part of the pterygoidal portion of the nasal septum,
and the thin plate which, on each side, passes up to be
united to the descending process of the " pre-frontal." In
THE SKELETON OF THE VERTEBRATE HEAD. 135
disarticulating the skull of the crocodile the pterygoids
generally remain attached to the post-sphenoidal centrum, so
that the prolonged anterior processes of the former present
the appearance of being elongations of the latter, which they
in fact are not.
From the foregoing considerations, and on grounds to be
explained in the sequel, when the palatine arch or haemal arch
of the pre-sphenoidal sclerotome conies to be examined, I recog-
nise in the crocodilian vomer of Cuvier and Owen the proximal
or upper element of the pre-sphenoidal haemal arch the same
element to which, when existing in certain fishes, Professor
Owen applies the sufficiently expressive term ento-pterygoid.
It will now be observed, that in consequence of the great
development of the pterygoids, and of the ento-pterygoids in
the crocodilian, the latter, extending forward into the neural
space of the ethmoidal sclerotome, roof over the greater part,
and provide a septum for nearly the whole of that extent of
the nasal fossse, the sides and floors of which are formed by
the so-called " palatals" or ethmoidal neurapophyses, and abut
against the descending processes of the " pre-frontals" or
ethmoido-frontals, without entirely extruding the neurapo-
physes from these processes, as in the chelonian. There is
another minor difference between these parts in the croco-
dilian and chelonian. In the chelonian, as has been already
stated, the ento-pterygoids having pushed the ethmoidal neu-
rapophyses from their natural connection with the descending
processes of the ethmoido-frontals, complete, by means of their
ascending divergent processes, the triangular space for the
olfactory nerves. In the crocodilian, again, the descending
processes of the ethmoido-frontals complete the space for the
olfactory nerves, by means of a short process from each of
them, which, passing inwards, meets its fellow of the opposite
side a little above the junctions of the descending processes
themselves with the ento-pterygoids. The space left between
136 ON THE MORPHOLOGICAL CONSTITUTION OF
this transverse commissure above, the combined ento-ptery-
goids below, and the lower ends of the descending ethmoido-
frontal processes laterally, is occupied by a prolongation for-
wards of the cartilaginous bar-like pre-sphenoidal centrum.
If the bones hitherto considered by comparative anatomists
as the " palatines" in the crocodilian, are in reality the neu-
rapophyses of its ethmoidal sclerotome, the question arises
Where are the actual palate-bones ? This question comes to
be examined in the sequel, when the haemal arch of the pre-
sphenoidal sclerotome, of which these bones are elements, is
, under consideration. At present I may state that the study
of the crania of the bird, lacertian, and ophidian, has led me
to recognise as the palate-bone that bone which Cuvier was
induced to consider peculiar to the lizard and serpent, and
named "os transverse" or "pterygoide externe;" and which
Professor Owen also names ecto-pterygoid.
The Ethmoidal Neural Arch and Centrum in the Lacer-
tians. The maxillaries of the typical lacertians are invariably
connected above to the so-called pre-frontals. These pre-
frontals are widely separated from one another by the anterior
extremities of the so-called " principal frontals," which pass
forward, and bound laterally the divided or undivided nasals.
The pre-frontals bound the anterior superior angles of the
orbits, sending downwards on each side a plate which sepa-
rates the orbit from the nasal cavity, is more or less intimately
connected with the so-called " double vomer," and with the
so-called " palatines." I shall, in the sequel, state the grounds
on which I hold the " palatines " of the lizard, ophidian, and
amphibian, to be its ento-pterygoids, and to be the homologues
of the bone or bones which in the bird are considered as the
" vomer." I believe the " transverse bones" of the lizard to be
actually its palate-bones, pushed backwards and outwards by
the greatly-developed ento-pterygoids, and of its so-called
vomer" of the lizard consists of two
THE SKELETON OF THE VERTEBRATE HEAD. 137
bones, which form the floor of the nostrils, separated from,
but at the same time connected to, one another by the lower
margin of the cartilaginous nasal septum, abutting against the
intermaxillaries in front, and the so-called "palatines" or
ento-pterygoids behind, and leaving a space on each side,
wider behind than before, between their outer margins and
the maxillaries, for the posterior nares. In some lizards the
posterior extremities of the two halves of the " vomer" are
separated from the transverse descending plates of the " pre-
frontals" by the interposition of the anterior extremities of
the ento-pterygoids, but in others they articulate with the
pre-fronto-lachryrnal. Anatomists appear to have been in-
duced to look upon these two bones in the lizard as the two
halves of the vomer, by the same circumstance which has
induced them to consider the ento-pterygoids of the bird as its
vomer viz. their position between the posterior nares. But
the general relations of the so-called double "vomer" of the
lizard indicate that its two halves are homologous with the
ethmoidal palate-plates of the chelonian, with the so-called
"palatines" or ethmoidal neurapophyses of the crocodilian,
with the corresponding cartilaginous or osseous pieces in the
bird, and with the lateral masses of the ethmoid in the mam-
mal. It appears to me that the ethmoidal neural arch and
centrum form a catacentric arrangement, the two compart-
ments of which constitute the greater part of the nasal fossae, the
olfactory nerves entering through the mesially divided space
between the descending or orbito-nasal processes of the meta-
neurapophyses ; and the posterior nares passing off on the outer
sides, and between the neurapophyses and the maxillaries.
The Ethmoidal Neural Arch and Centrum in Ophidians.
The maxillaries of the serpent are articulated or connected to
the " pre-frontals." The latter are separated from one another
mesially by the elongation of the nasals back to the " principal
frontals." Each of the "pre-frontals," comparatively large
138 ON THE MORPHOLOGICAL CONSTITUTION OF
and anchylosed to the lachrymal, sends down a transverse
orbito-nasal plate, notched on its inner margin for the olfactory
nerve, but separated from its fellow of the opposite side by
the pre-sphenoidal processes of attachment of the " palatines."
The space roofed over by the nasals and "pre-frontals" is
mesially divided above by the contiguous mesial descending
laminae of the nasals, and below by the cartilaginous nasal
septum. It is floored by the double " vomer," the two halves
of which, connected by the lower margin of the cartilaginous
septum, extend from the intermaxillaries in front to the cen-
trum of the pre-sphenoidal sclerotome behind, being separated
from the orbito-nasal processes of the " pre-frontals" by the
pre-sphenoidal processes of the " palatines."
From what has already been stated with reference to the
corresponding parts in the bird, the chelonian, and saurian
reptile, it will now be seen that I hold the so-called " pre-
frontals" of the serpent to be its actual frontals or ethmoido-
frontals ; its so-called double " vomer" to consist of the right
and left neurapophyses, as the " pre-frontals" are the two halves
of the meta-neurapophyses ; and the cartilaginous nasal septum
the centrum of its ethmoidal sclerotome.
The Ethmoidal Neural Arch and Centrum inthe Amphibians.
The view which I take of these parts in the Amphibia will
at once appear from the foregoing statements, and may be illus-
trated by the structure in the frog. As in the bird, the basis
of the ethmoidal neural arch and centrum consists of that por-
tion of the persistent primordial cranium which is situated
behind the intermaxillary region, and immediately in front of
the " os a ceinture." The mesial portion of this mass of car-
tilage forms the centrum of the sclerotome, as the posterior
part of the nasal septum. The posterior portions of the nasal
fossae are hollowed out on its sides. Its upper surface is
covered by the so-called "pre-frontals," which are, in fact,
ethmoidal-frontals, or the two halves of the divided meta-
THE SKELETON OF THE VERTEBRATE HEAD. 139
neurapophyses. Its lower surface is supported by the two
triangular bones, covered with teeth, and which are the neura-
pophyseal ethmoidal elements, already examined in the other
Vertebrata, The posterior nares are situated behind, between
the outer margins of these so-called vomerine bones and the
maxillaries. The latter are, as usual, connected to the eth-
inoido-frontals.
Of the Views which have been hitherto taken of the Ethmoidal
or Nasal Vertebra, or Sclerotome. I am precluded in an ab-
stract from entering upon the important but tangled morpho-
logical history of the nasal segment of the cranium. I shall
only, therefore, on this department of the subject, make a few
observations, in deference to the authority of Professor Owen,
and in explanation of those points on which I find myself at
variance with his doctrine. I have already so far stated, and
in the sequel shall more fully state, the grounds on which I
dissent from the doctrine of Oken and Bojanus, adopted by
Professor Owen, that the nasals and vomer are respectively
the neural spine and body of the nasal vertebra. What I in-
tend more particularly to notice at present is that part of Pro-
fessor Owen's doctrine which relates to the neurapophyseal
elements of the nasal vertebra.
Professor Owen considers the middle plate of the mam-
malian ethmoid to be the coalesced pre-frontals, and the two
halves of the cribriform plate, the ethmoidal cellules, . and
turbinated laminse, to be collectively the greatly-developed
olfactory capsules. If the latter are kept out of view, as not
entering, according to his doctrine, into the formation of the
ethmoidal or nasal neural arch, the doctrine necessitates the
conversion of the laterally-placed "pre-frontals" of the fish
and reptile into a single mesial laminar bone. Here I would
observe that, overlooking for the present the adoption by Pro-
fessor Owen of the current statements as to the identity of
the "pre-frontals" of the fish with the "pre-frontals" of the
140 ON THE MORPHOLOGICAL CONSTITUTION OF
reptile, I cannot conceive how the " pre-frontals," either of
the fish or reptile, can be homologous with a mesial bone.
Embryologlcally, I cannot understand how the olfactory nerves,
which in the fish and reptiles are situated mesiadof the "pre-
frontals," can become placed in the mammal on their outer
aspects. The pair of " pre-frontals" in the crocodile or turtle
can be legitimately enough conceived as coalescing mesially
into a single bone ; but this change presupposes the with-
drawal or obliteration of the olfactory nerves ; for, otherwise,
two conditions must be admitted, both of which are ernbryo-
logically untenable first, that the olfactory lobes of the
mammal are at one period in its development mesiad to the
right and left halves of its central ethmoidal plate ; and
secondly, that the nervous and sclerous structures change
places, the former passing outwards through the latter, or the
latter meeting in front of the former, and passing backwards
between them. But the actual facts are these : The mesial
plate, or bar, of the mammalian ethmoid is mesial from the
first ; and the olfactory bulbs, or nerves, are situated from the
first on its lateral aspects. The mesial plate is the prolonga-
tion forward of the central bar of the primordial cranium ; it
is a true vertebral centrum, and is continued onwards and
downwards into the vomerine portion of the cranial axis. The
cribriform lamellae are the only parts, therefore, of the mam-
malian ethmoid which present in their embryo and adult con-
ditions all the characters of neurapophyseal elements ; con-
nected below with their centrum, and laterally or above with
their frontal meta-neurapophyses, they, along with the latter
and the centrum, close in the fore part of the encephalic portion
of the cranial cavity, and enclose the olfactory lobes of the
brain. That the olfactory, like the fifth nerve of the mammal,
leaves the encephalic cavity by more than one orifice, and that
the olfactory <: sense-capsules" are united to the corresponding
neurapophyses, are circumstances which afford no arguments
THE SKELETON OF THE VERTEBRATE HEAD. 141
against this determination, but, on the contrary, are in accord-
ance with the union of the auditory capsules with their cor-
responding neurapophyses, and the exit of the auditory nerve
from the encephalic cavity in divisions. It must also be ob-
served, that if we are to look, with Professor Owen, upon the
central lamina or bar of the mammalian ethmoid as the result
of the mesial union of a pair of " pre-frontals," we must assign
a morphological reason for the co-existence of a mesial car-
tilaginous septum with divided "pre-frontals" of the reptile
and fish.
I am also obliged to dissent from Professor Owen's deter-
mination of the so-called " ethmoid" of the bird as the mesially-
united neurapophyses of its nasal vertebra. Apparently in-
fluenced by its usual designation, and restricted to his own view
of its homology by his determination of the " basi-sphenoid"
as consisting of the connate centrums of the "mesencephalic"
and "prosencephalic" vertebrae, Mr. Owen has in the bird, as
in the mammal, arranged this portion of his morphological
system in opposition to embryological facts. The two olfactory
nerves of the bird pass forward on each side of the so-called
" ethmoid" in shallow grooves ; in certain instances only do
they pass through notches or complete orifices formed by
osseous development from the two surfaces of the bone. The
two nerves in no instance pass forwards between the plates of
the bone in any part of their extent. At no period during
development are the olfactory nerves of the bird situated
rnesiad of any part of this bone ; for it is originally a mesial
cartilaginous plate, a portion of the axis of the primordial
cranium, extending forwards and upwards from that part of
the primordial axis which, when ossified, constitutes the
anterior or acuminated extremity of the centrum of the post-
sphenoidal sclerotome. In the sequel I shall have to point
out that this bone in the bird, which anatomists have hitherto
looked upon as the " ethmoid," is, in fact, the body or centrum
142 ON THE MORPHOLOGICAL CONSTITUTION OF
of the pre-sphenoidal sclerotome converted into a mesial plate
extending up to and flattened out at the upper surface of the
cranium, in accordance with the catacentric character of the
neural arch of the sclerotome, of which it is an element. Its
corresponding neurapophyses are the pre-sphenoidal wings
the " orbito-sphenoids" of Professor Owen which not only
bound laterally the orifices for the optic, but also those for the
olfactory nerves. The so-called " ethmoid" of the bird is not
therefore formed by the coalescence of a pair of " pre-frontals,"
but is a mesial element belonging to another sclerotome. The
bird already possesses distinct or "divided" "pre-frontals,"
with all the characters of the "pre-frontals" of the reptile in
its so-called " nasals."
Duge*s considered the " os en ceinture " of the frog to be
the ethmoid, from its giving passage to the olfactory nerves
by two funnel-shaped orifices at its anterior extremity, and
from its intimate connection with the nasal cartilage in front.
Professor Owen, on the same grounds, while he holds the pos-
terior part of this bone in the Eana loans to consist of the
" orbito-sphenoids," looks upon its anterior part as the confluent
"pre-frontals." But as the "os en ceinture" of the common
frog originates in a centre of ossification on each side of its
fundamental portion of the primordial cranium. ; and as Pro-
fessor Owen does not state the grounds on which he holds the
" orbito-sphenoids " to be confluent with it in the bull-frog ;
as I can find no trace of such confluence either in the bull-frog
or common frog, and as the fore part of the bone is divided by a
mesial septum, I look upon it as consisting of a single pair
of neurapophyses and a catacentric septum. As this " os en
ceinture " is situated upon the upper surface of the anterior
acuminated portion of the centrum of the post- sphenoid, as in
the bird, and as it is covered above, and in the common frog
is united with the anterior portion of the so-called " parieto-
frontal," it appears to me to constitute the neural arch and
THE SKELETON OF THE VERTEBRATE HEAD. 143
centrum of the pre-sphenoidal sclerotome, of which the orbito-
sphenoids are the neurapophyses. The proper "os en ceinture"
of Cuvier is in fact the homologous structure in the aneurous
batrachian with the so-called "ethmoid," and the orbito-
sphenoids collectively in the bird ; the centrum being prin-
cipally developed in the latter, the neurapophyseal elements
in the former. On these grounds, and also because I hold,
with Cuvier, the * nasals " of the frog to be its " pre-frontals,"
I cannot assent to Professor Owen's doctrine that the " os en
ceinture " exhibits a stage in the mesial coalescence of a pair
of " pre-frontals," the final effect of which is the formation of
a mesial ethmoidal plate, or mesially-united nasal neura-
pophyses.
On the Actinapophyses of the Ethmoidal Sclerotome. As
the radiating elements of the ethmoidal segment of the skull
are numerous and important, and as their elucidation requires
a more extended reference to corresponding elements in the
succeeding sclerotomes than can be made before the exami-
nation of these has been entered upon, I shall at present make
only a general statement on the subject.
In the mammal we find a series of sclerous elements
arranged from above downwards on each side of the ethmoidal
sclerotome. On its upper or neural portion are the olfactory
" capsule " and the lachrymal bone. On the lower or haemal
portion, the cartilages of the eyelids, with the inferior turbi-
nated and malar bones. If the secondary antero-posterior
elongation of the maxillary be kept out of view ; and if it be
conceived in its fundamental developmentary form as a rib-
like bone, the convexity of which is inclined outwards and
backwards ; and if, at the same time, the possibility of a double
arrangement of actinapophyseal elements in each sclerotome
be borne in view, it will be seen that the malar extends out-
wards and backwards from the anterior or outer ; the inferior
turbinal from the posterior or inner aspect of the bone. I
144 ON THE MORPHOLOGICAL CONSTITUTION OF
have already stated that the actinapophyseal elements of the
cranium are generally flattened or extended so as to abut
against one another, and against the other bones of the skull.
Thus the malar passes backwards in the fibrous membrane
which extends across the orbital opening, and which covers in
the temporal fossa. The final purpose of the malar is to afford
an abutment against the squamosal so as to strengthen the
flank of the mammalian head. The malar, therefore, in many
instances sends secondary processes upwards and inwards to
abut against other bones. While I gladly avail myself of
Professor Owen's term " squamosal," and fully agree with him
as to the bone itself being a "radiating" element of the
cranium ; and while I more particularly assent to his very
beautiful determination of it as the " quadrate jugal " of the
bird, I must, nevertheless, contend for the much greater pro-
bability of its being a radiating element of the mandibular
than of the maxillary arch. Its intimate connection with the
quadrate bone in the development of the chick, and the dis-
union of it and the malar in certain Mammalia, appear to me
to indicate that they belong to distinct sclerotomes.
The extended attachment from above downwards of the
inferior turbinal to the inner aspect of the maxillary of the
foetal ruminant, a form of attachment which is repeated in
the lachrymal process of the bone in the human subject, in-
dicates the primary actinapophyseal form of the bone. Its
elongation backwards on the inner aspect of the palate-bone,
and its prolongation forward to abut against the cartilaginous
actinapophysis of the vomerine haemal arch, are secondary
processes in the development of the bone, and steps towards
the completion of that antero-posterior system of serially
homologous actinapophyses which constitute what may be
termed the inferior turbinal system. The inferior concha is
peculiar to the nasal fossa of the mammal. The sclerous
elements, which constitute its skeleton, in its most fully de-
THE SKELETON OF THE VERTEBRATE HEAD. 145
veloped form, are posterior or inner actinapophyses of the
rhinal, vomerine, and ethmoidal haemal arches. These actina-
pophyses become included in the nasal fossa by the closure
of the metasomatomic clefts ; and, as they subsequently
elongate, they abut against one another in the antero-posterior
direction.
I shall, in the sequel, show that the more or less denned
space termed orbit, at the side of the mammalian cranium, is
fundamentally the metasomatomic fissure between the eth-
moidal and pre-sphenoidal sclerotomes. The upper part of
this fissure continues permanently open as the lachrymal
canal, and drains away the secretion which bathes the front
of the eyeball, while that organ, supported by the sclerotic,
which is a pre-sphenoidal neuractinapophysis, and surrounded
by its accessory structures, is lodged in its dilated portion.
From the upper, anterior, and lower orbital margins, which
are formed by elements of the anterior of its two bounding
primary sclerotomes, a fibrous membrane extends backwards,
covered externally by the orbicular muscle, and closing in the
contents of the orbit, with the exception of the front of the
eye, exposed through the palpebral fissure. This fibrous
membrane is a metasomatomic or actinal lamina, extending
very obliquely outwards and backwards like an operculum
over the orbit. The succeeding metasomatomic membrane
assumes the form of the tissue which separates the orbit from
the temporal fossa, and which, passing backwards external to
that fossa, forms the temporal fascia which constitutes an
operculum to that space. The temporal fossa itself is the
upper portion of the metasomatomic fissure between the pre-
and post-sphenoidal sclerotomes, occupied by the muscles of
mastication and the homologous nerve ; the lower part of the
fissure on each side remaining permanently open as the mouth,
or more correctly as the anterior opening of the isthmus of
the fauces. By the extension of ossification from neighbouring
L
146 ON THE MORPHOLOGICAL CONSTITUTION OF
bones into the anterior and external portion of this fibrous
layer, the orbit may be more or less shut off from the temporal
fossa.
The cartilaginous laminae which support the eyelids of the
mammal are developed in the fibrous layer which constitutes
the operculum of the orbit, and lie in the same morphological
plane as the malar and lachrymal bones. Their histologies!,
as well as morphological relations appear to me to indicate
not only that the palpebral cartilages are actinal elements of
the endo-sclerome, but also that they are anterior or external
hasmactinapophyses of the ethmoidal sclerotome. This view
of the morphological relations of the malar bone, palpebral
cartilages, and opercular membrane of the orbit in the mam-
mal, is borne out by the corresponding arrangement in the
bird. A fibrous membrane extends backwards over the orbit,
from the posterior extremity of the feebly-developed'maxillary,
and from the posterior margin of the descending process of
the ethmoido-frontal. In the lower part of this membrane the
malar is imbedded ; across its centre the palpebral cartilage ;
and at the antero-superior angle of the orbit, the lachrymal
bone. These have all distinct actinapophyseal characters,
which, in the case of the lachrymal, enables us to perceive
more clearly how the mammalian lachrymal, having become
intercalated between its corresponding hsemapophysis and
neurapophysis, retains only so much of its actinapophyseal
character as is indicated in the anterior margin of its groove,
the remainder of the bone being a secondary expansion.
The lachrymal bone of the bird may extend into the
orbital membrane along the outer margin of the so-called
" principal frontal," or sphenoido-frontal, and become attached
to that bone without losing its connection with the ethmoido-
frontal. It may thus also form a union with the supra-orbital
bone, when that bone is present, as in the hawks. The
lachrymal may, moreover, extend backwards under the eye to
THE SKELETON OF THE VERTEBRATE HEAD. 14Y
the post-frontal process, and may have a branch of communi-
cation with the antero-inferior projection of the mastoid, as in
certain parrots. It may also extend down to the malar, and
may be connected in this direction with the transverse pro-
jection of the so-called " ethmoid," or pre-sphenoidal centrum.
The infra-ocular bony arch in the maccaws and certain other
birds is not a zygornatic arch, although consisting like it of
actinapophyseal elements. The proper zygomatic arch, as
consisting of the malar and squamosal, exists in all birds ;
the infra-ocular arch is ossified in comparatively few.
The reference of the lachrymal and the other bony forma-
tions round the orbit in birds to a muco-dermal system by
the continental anatomists and by Professor Owen, appears to
me to be disproved by their relation to the soft parts. They
are all developed in aponeurotic bands, which enter into the
formation of the orbital fascia already alluded to. In a band
extending along the margin of the sphenoido-frontal, the
supra-orbital bone takes its rise, which may thus become con-
nected with the lachrymal, when that bone, which is developed
in the anterior extremity of the band, extends backwards in it.
A second band extends downwards and backwards from the
lachrymal to the malar, forming a ligament between the two
bones, and along which ossification may extend. A third
band extends from the post-frontal process downwards and
forwards to the quadrate-jugal or squamosal, along which
ossification may extend from above. In all birds a band
connects the lachrymo-malar with the post-fronto-squamosal
band, thus forming an arch below the under eyelid. The ex-
tension of ossification into this commissural band, probably
from both extremities, completes the infra-orbital bony arch,
and may approximate or unite it to the squamoso-jugal or
proper zygomatic arch. A fibrous band, which extends down-
wards and forwards in the temporal fascia from the anterior
process of the mastoid, becomes ossified in some birds ; and
148 ON THE MORPHOLOGICAL CONSTITUTION OF
it is an extention of this ossification which appears to form
the mastoidal limb, or attachment of the infra-ocular arch of
the maccaw. I shall, in the sequel, state the grounds on which
I regard as actinapophyseal all the bones developed in the
opercular membrane of the orbital of the bird. I regard the
lachrymal bone and the supra-orbital bone or bones of the
saurians, as referable to the same morphological category ;
and as due to arrangements in the fibrous operculum of the
orbit, similar to those in the bird ; as also the connection be-
tween the malar and the post-frontal of the crocodilian, as
well as the change in the direction of the jugal, and the
peculiar position of the squamosal in the typical lizards.
The supra-orbital bone or cartilage, with the infra-ocular
bony arch, appears in various forms in the osseous fish ; and
the arrangements presented by this form of cranium clearly
indicate that these orbital bones are parts of a system of
actinapophyseal elements referable respectively to the eth-
moidal, pre- and post-sphenoidal, temporal, and occipital
sclerotomes, peculiarly modified and connected in front for
the protection of the orbit, and behind for the suspension of
the pectoral girdle.
THE PRE-SPHENOIDAL SCLEROTOME. Its Centrum and
Neural Arch. It has been already stated that this sclerotome
is peculiar in the mammal, in the absence of its meta-
neurapophyses, while this mesial element is more or less fully
and largely developed in the other forms of Vertebrata. When
the cerebrum proper is developed, the sphenoido-frontal bone
is absent ; when the cerebrum proper is a mere film, as in
birds and reptiles, or is absent altogether, the sphenoido-frontal
is present. As the evidence on which this statement is based
is derived from the consideration of the varied relations of all
the primary elements in the different forms of cranium, I am
compelled, in this preliminary abstract, to refer those who are
desirous of weighing that evidence to what has been already
THE SKELETON OF THE VERTEBEATE HEAD. 149
adduced with regard to the ethmoido-frontals, and to the
statements to be afterwards made in regard to the meta-
neurapophyses of the post-sphenoidal and temporal sclero-
tomes. In the meantime, I shall confine myself to a general
exposition of the arrangement as I regard it.
The anterior part of the body of the human sphenoid, and
the corresponding pre-sphenoidal piece in the Mammalia gene-
rally, constitute an undoubted centrum, to which the lesser,
anterior, or orbito-sphenoidal wings, are the corresponding
neurapophyses.
How far we may be entitled to assume the frequent
" triquetral " bones in the coronal suture in the human, and
in certain other mammalian crania, and the separately-de-
veloped antlers of the giraffe, as indications of the missing
bone, remains to be determined. I would only observe at
present, that the great extent and permanency of the anterior
fontanelle appear to be connected with the deficiency in
question.
I have already stated that I regard the so-called " principal
frontal " of the bird as the missing frontal of the mammal.
Distinguishing it as sphenoido-frontal, it is the divided meta-
neurapophysis corresponding to the feebly-developed " orbito-
sphenoids," which, bounding the optic and olfactory orifices,
constitute the neurapophyses, and to the so-called " ethmoid "
as the centrum of the pre-sphenoidal sclerotome. Assuming
for the present the signification I have attached to the " prin-
cipal frontals," and holding the neurapophyseal character of
the orbito-sphenoids as incontestable, I would only add a few
remarks regarding the central element. The determination of
the "ethmoid" of the birds as the centrum of the pre-sphenoidal
segment of the cranium, while it does not require Professor
Owen's hypothesis of connation of this element with the cen-
trum behind, presents the element under a form similar to
that exhibited by the ethmoidal and vomerine centrums. It
150 ON THE MORPHOLOGICAL CONSTITUTION OF
resembles these in being an ossified portion of the primordial
axis of the cranium, in being flattened into a horizontal plate
at its upper margin, in extending down to the line of the base
of the skull, and in thus presenting a catacentric relation to
its neural arch. The passage of the anterior acuminated ex-
tremity of the centrum behind beneath the lower margin of
the pre-sphenoidal centrum, so as to support it, is merely an
example of that longitudinal obliquity in the setting of cranial
centrums against one another, which may be considered as the
rule rather than an exception. The posterior margin of the
bone is oblique from below upwards and forwards ; gives
attachment to the orbito-sphenoids, or to their membranous
neurapophyseal substitutes, which bound or give passage to
the orbital and olfactory nerves. The obliquity of this margin
of the bone corresponds with the similar obliquity of the fore
part of the basis of the brain of the bird, a remarkable feature
in its configuration. The flattened upper edge of the bone may
be more or less exposed on the upper surface of the cranium ;
and when the intermaxillaries, ethmoido- and sphenoido-
frontals are removed, this flattened margin is found to be
similar to and continuous with the flattened upper margin of
the ethmoidal and vomerine cartilaginous septum. The
anterior margin may be nearly perpendicular, but is generally
oblique from below upwards and forwards, concave or concavo-
convex, sharp, and generally free, being connected to the
posterior margin of the ethmoidal cartilaginous septum by
membrane, thus permitting, more or less, movement of the
upper mandible that is of the combined ethmoidal and
vomerine sclerotomes on the pre-sphenoidal.
In the majority of birds a laminar process projects out-
wards and downwards from the lower and fore part of this
bone. This process, variously developed, forms, along with
the descending process of the lachrymal, the anterior wall of
the orbit, separating it from the nasal space, and permitting
THE SKELETON OF THE VERTEBRATE HEAD. 151
the passage of the olfactory nerve through a notch or hole in
its upper edge. I regard this process on each side of the pre-
sphenoidal centrum as of the same nature as the process which
will be found projecting from each side of the lower part of
the ethmoidal septum or centrum, and which, abutting against
the descending process of the ethmoido-frontal, forms a wall
or rampart across the floor of the nasal passage, extending
nearly half-way up to its roof, immediately behind the ex-
ternal nostril, thus converting that part of the nasal chamber
in front of it into a vestibule. This process is largely de-
veloped in the ossified ethmoido-vomerine septum of the
hawks and owls.
I would here observe that the " os en forme de cuiller " of
Cuvier, which he considers as the inferior turbinal of the
lizard, and which forms the fore part of the floor of the nostril
on each side, and the convex anterior part of which stretches
like a buttress across the cavity, between the septum and the
maxillary, immediately behind the external nostril, appears
to me to be, with its fellow of the opposite side, merely the
ossified lower portion of the ethmoidal centrum. These so-
called " cornets inferieurs " of the lizard form the floor, and
do not, therefore, project from the outer wall of the nasal
passage in the manner of the inferior turbinals ; and I believe
anatomists will, in reviewing the subject, admit that the in-
ferior turbinal accompanies the fully-completed maxillary
arch, and only exists, therefore, in the mammal.
I regard these lateral processes of the ethmoidal and pre-
sphenoidal centrums of the bird as homologous with the
pterygoid processes of the post-sphenoidal centrum, and
generally with those processes which, under various forms,
project downwards from the sides of the lower or haemal
aspects of the occipital and succeeding centrums in certain
fish, or with those processes termed " hypopophyses" by
Professor Owen.
152 ON THE MORPHOLOGICAL CONSTITUTION OF
Before dismissing the consideration of this important cen-
trum in the bird, I would direct attention to certain interesting
modifications which it may undergo. In the first place, it
may, like many other bones in the cranium of the bird, become
greatly dilated and altered in form by the development of
air-cells in its interior. The pneumatic openings are two in
number, one on each side of the anterior margin below the
superior horizontal plate. The pneumatic excavation and
dilatation extends backwards more or less in certain species ;
and in some owls the bone presents the form of a cubical
cellular mass. This peculiarity of form might be adduced in
support of Professor Owen's doctrine of the formation of this
bone from the coalescence of the pre-frontals ; but then it
will be observed that the increased breadth of the bone is not
due to incomplete mesial fusion of lateral parts, but to ex-
pansion from the mesial plane, for the olfactory nerves still
run forwards in grooves on its lateral aspects, although these
may be deep in front, and posteriorly their margins may
overlap the nerves. The expansion of the pre-sphenoidal
centrum also produces a remarkable separation of the optic
foramina. As explanatory of this effect, I would observe,
that the development of this bone in the chick shows that it
forms the posterior border of the common optic foramen by
means of a pair of processes which project from its posterior
inferior angle like the limbs of the letter Y. When, therefore,
the bone takes on transverse dimension, the single optic chasm
separates into two optic foramina, which, in Strix flammea
are three-eighths of an inch asunder.
The separation of the optic foramina from the pneumatic
expansion of the pre-sphenoidal centrum leads me, in the
second place, to observe, that the characteristic separation of
these orifices in the extinct forms Dodo, Dinornis, Palapteryx,
did not depend entirely on pneumatic expansion of the pre-
sphenoidal centrum, nor on such width of that bone as might
THE SKELETON OF THE VERTEBRATE HEAD. 153
be attributed to incomplete mesial fusion of a pair of " pre-
frontals," but on the remarkable prolongation backwards on
eacli of its sides of the neurapophyseal walls of the ethmoidal
olfactory chambers.
Professor Owen, in his series of graphic and valuable
memoirs on these three extinct forms, and in his memoirs on
Apteryx, assuming the pre-frontal doctrine regarding the bone
in question, and directing special attention to the more or less
complete passage backwards of the nasal chambers to the an-
terior or inferior wall of the cranial cavity, and to the passage
of the olfactory nerves into these by a number of orifices,
apparently recognises in Apteryx, for instance (although he
does not directly make the statement), a completed mammalian
ethmoid. Now, recalling attention again to the embryological
considerations from which the formation of neither the
mammalian ethmoidal septum, nor the so-called ethmoid of
the Ostrich, Dinornis, Dodo, nor Apteryx, can be conceived as
resulting from coalesced pre-frontals, I would remark, that
the arrangement of the nasal fossae in Apteryx, instead of
being mammalian, presents the peculiar ornithic character of
its parts, fully brought out ; all the phases in the develop-
ment of which may be observed in the series of birds. In all
birds, the posterior extremities of the cartilaginous pouchlike
ethmoido-neural, or olfactory chambers, approach or encroach
upon the sides of the pre-sphenoidal centrum ; so that the
membrane, which connects its anterior margin to the cartila-
ginous nasal septum, and a certain extent of both its surfaces,
separates the two pouches from one another. The laminar or
hypopophyseal process on each side of the bone, variously
modified in form, limits, posteriorly and inferiorly, the olfactory
portion of the lateral surface of the bone, and, folded over the
pouch, walls it in more or less from below ; while the
lachrymal from above passes down on its outer side. The
gradual environment of the pouch may be traced in the series
154 ON THE MORPHOLOGICAL CONSTITUTION OF
of birds ; and I find in the Asiatic Cassowary, the stage imme-
diately preceding the completion of the process in Apteryx.
In this bird, the pair of deep fossse in the interior of the skull,
which lodge the olfactory lobes, are separated from one an-
other by the posterior margin of the pre-sphenoidal centrum,
which here represents the crista galli. The plate of bone which
forms the floor of each fossa, instead of being cribriform, as in
Apteryx, is perforated by a single star-like foramen, a form due
to the partial shooting across of bony processes from its margin.
In the Chelonian. The neural arch and centrum of the
chelonian are represented in the dry skull by the pair of
bones usually considered as the " proper frontals," but which
I regard as sphenoido-frontals. In the recent condition the
centrum appears in the form of a compressed cartilaginous
bar, continuous posteriorly with the compressed anterior part
of the post-sphenoidal centrum, resting below on the conjoined
pterygoids and ento-pterygoids, continuous in front with the
cartilaginous ethmoidal septum or centrum, and thus pre-
senting all the relations of the pre-sphenoidal centrum of the
bird. It is continued upwards, and represents the orbito-
sphenoids, or neurapophyses, in the form of a double fibro-
cartilaginous membrane, the two laminae of which separate to
unite with the posterior margins of the orbito-nasal processes of
the ethmoido-frontals, with the two parallel descending ridges
of the sphenoido-frontals, and with the anterior margins of the
peculiar descending processes of the so-called " parietals." The
olfactory nerves pass forwards between these neurapophyseal
laminae above ; and the optic, with the other orbital nerves,
perforates them.
In the Crocodilian. In the crocodiles, the sphenoido-
frontals have coalesced ; but the cartilaginous centrum and
neurapophyseal interorbital laminae present exactly the same
relations as in the chelonian ; the only difference being the
result of the union of the orbito-nasal processes of the
THE SKELETON OF THE VERTEBRATE HEAD. 155
sphenoido-frontals near their lower extremities, and the con-
sequent space left between this bony bridge and the deep
furrow formed by the inclined upper surfaces of the ento-
pterygoideal portions of the pterygoids.
In' the Lacertians. In the lizards, the sphenoido-frontal
is again double. In consequence of the mesial separation of
the ento-pterygoids ("palatals") and pterygoids, the elongated
fibre-cartilaginous centrum and neurapophyseal interorbital
laminae, are left unsupported below ; to which circumstance
is probably due the formation in the interorbital laminae of a
pair of delicate triradial osseous neurapophyses, which pass
off from the upper margins of the optic foramina.
In the Ophidian and Batrachian. Leaving the further
consideration of the special homology of the anterior sphenoidal
wing in the reptiles, and more especially in the crocodiles,
until the posterior sphenoidal wing, and the so-called "petrosal,"
have been examined, I would observe, that the grounds on
which Professor Owen distinguishes the "os en ceinture"
of the frog, from that segment in the python which includes
the so-called "frontals," appear to me somewhat arbitrary.
This segment in the serpent consists of a pair of neurapophyses,
or orbito-sphenoids, which are distinct, as cartilages at least,
in the embryo ; of a double meta-neurapophysis (sphenoido-
frontals), which not only occupy on each side the positions of the
neurapophyses, but extend the fore part of their inner margins
downwards, back to back, in the mesial plane, on the sides of
the compressed centrum ; which thus, along with them,
divides the neural chamber in front, for the transmission of
the olfactory nerves. The sides of the " os en ceinture " are
formed by neurapophyses ; while the so-called " frontals " of
the serpent occupy the greater part at least of the sides of
their segment ; in other respects, their relations are similar.
They are both catacentric ; the centrum, in both, resting, as
in the bird, on the upper surface of the anterior acuminated
156 ON THE MORPHOLOGICAL CONSTITUTION OF
extremity of the post-sphenoidal centrum, and in the plane of
the ethmoidal centrum in front. I regard, therefore, the
" os en ceinture " in the Batrachian, along with the anterior
segments of its " parieto-frontals," as consisting of the centrum,
neurapophyses, and meta-neurapophyses of the pre-sphenoidal
sclerotome ; and, therefore, also as homologous with that seg-
ment in the ophidian which includes its " frontals," but
exclusive of the elongated anterior prolongation of the post-
sphenoidal centrum.
The Pre-sphenoidal Centrum and Neural Arch in the Fish.
The bone which predominates over every other in the cranium
of the fish is the so-called "principal frontal ;" which, how-
ever, as already stated, I do not regard as the frontal or
ethmoido-frontal of the mammal, but as a sphenoido-frontal.
It is the pre-sphenoidal meta-neurapophysis of the fish, pre-
senting all the relations of the corresponding bone or bones in
the bird, chelonian, and lizard, except that the ethmoido-
frontals anterior to it have coalesced in the middle line ; while
the ethmoidal neurapophyses have become so much developed,
exposed, and connected to it laterally, as to assume the position
of the so-called " nasals " and " pre-frontals " in the bird and
reptile. The enormous development of this bone in the fish
and bird appears to depend on the great bulk of the organs of
vision. There is, therefore, in both, an extended interorbital
space to be filled up. In the fish, as in the bird, this is vari-
ously effected by means of fibro-cartilage and bone. The
extreme forms of the interorbital arrangement may be illus-
trated by the gadoid and cyprinoid fishes. In the cod the
greater part of the so-called interorbital septum consists, as
in the chelonian and lizard, of a double fibrous membrane,
which extends upwards from the anterior prolongation of the
post-sphenoidal centrum to the margins of the mesial grooves
on the under surface of the sphenoido-frontal. The two
laminse of this membrane thus bound the sides of the
THE SKELETON OF THE VERTEBRATE HEAD. 157
compressed neural space, along the upper part of which the
olfactory nerves pass forward. In the posterior superior
part of each of these neurapophyseal fibrous laminae, a com-
paratively small plate of bone is developed, while the centrum
consists of the bar of persistent cartilage, which extends along
the grooved upper surface of the anterior portion of the post-
sphenoidal centrum, and terminates above the ethmoidal cen-
trum (" vomer "). The optic nerves pierce the membranes so
far back as to notch very deeply the anterior margins of the
post-sphenoidal ueurapophyses, or post-sphenoidal wings.
In the carp, again, the interorbital space is occupied above
by a considerable descent of the margins of the spheiioido-
frontal groove ; in front, by complete ossification of the fibrous
membranes, which thus become pre-sphenoidal neurapophyses ;
behind, by the passage forwards of the post-sphenoidal wings
(" ali-sphenoids "), through which, during development, the
optic nerves have passed back, to be lodged in notches in their
posterior margins ; and below, by the bar of semi-ossified
cartilage situated upon the upper surfaces of the posterior
sphenoidal and ethmoidal centrums.
Of the Hcemal Arch and Hcemactinagophyses of the Pre-
sphenoidal Sclerotome. The palatine arch, between which and
the mandibular the mouth is situated, and which terminates
therefore posteriorly the prestomal series of haemal arches,
may be presumed to undergo very varied modifications in
connection with the olfactory, the respiratory, and the digestive
functions. In the present instance, as in many others, the
anatomy of the human body, instead of leading astray by
complexity and extreme modification of its parts, supplies the
key for their morphological solution, by affording an example
of the employment of the fundamental type of structure for the
fulfilment of the most complex functional purposes.
The human pre-sphenoidal centrum, hollowed out by nasal
air-cells, as in certain birds, is bounded below and in front by
158 ON THE MORPHOLOGICAL CONSTITUTION OF
a pair of separate triangular-curved bony plates, which,
limiting the size of the right and left pneumatic orifices, brings
these into communication with the posterior ethmoidal air-cells
or sinuses. These " sphenoidal turbinated bones," or "bones
of Bertin," in contact along their outer margins, and outer part
of their inferior aspects, with the sphenoidal processes of the
palate-bones, constitute the upper elements or suspensory
extremities of the inverted arch, completed by the meeting of
the palate-bones themselves in the posterior part of the mesial
line of the palatal vault. The right and left pterygoids are
attached, as a pair of actinapophyses, to this arch. They pass
off backwards and outwards from the posterior margins of the
perpendicular plates of the palate-bones, and abut in the
embryo against the upper and fore part of the mandibular
arch, retaining in the tympanic processes of their adult
form indications of their early connection with that arch.
The most important secondary connection of the pterygoids
in the human adult is with the pterygoid processes of the
post-sphenoid ; and it is this sphenoidal connection which is
most frequently repeated in the animal series.
I shall not enter at present into the question of the
probable existence of "bones of Bertin" in the Mammalia
generally \ nor inquire whether the separate orbital pieces of
the palate-bones in the herbivorous Cetacea, according to
Cuvier, and the separate anterior portions of the pterygoids
of the young dolphin, as described by Meckel and Eapp, may
be indications of the upper elements of the palatal arch ; but
pass on to the consideration of the palatal arch in the lower
Vertebrata, in which the two elements of which it appears to
consist on each side are distinctly developed.
The Palatal Arch and Pterygoids in the Bird. The bone
hitherto considered by all anatomists as the vomer of the bird,
is a more or less elongated narrow plate, the margins of which
are bent upwards so as to convert its upper surface into a
THE SKELETON OF THE VERTEBRATE HEAD. 159
groove, which is applied against the under surface of the
acuminated anterior extremity of the post-sphenoidal centrum,
which is therefore interposed between it and the pre-sphenoidal
centrum. This bone, more or less compressed or extended
laterally, separates the posterior nostrils from one another.
Its anterior extremity reaches the anterior limits of these
orifices, or, passing forwards into the palate between the
ethmoidal neurapophyseal and maxillary palatal laminse, and
concealed more or less by them, may terminate on the surface
of the palate between the intermaxillary palatal plates. When
this bone is much compressed it is single throughout ; when
flattened, it is more or less extensively divided in the
mesial line.
The palate-bones of the bird, more or less elongated,
extend anteriorly under the maxillary palatal lamina, to
which in general they are only slightly connected, forward to
the intermaxillary palate-plates, with which they are anchylosed
or articulated, separated from one another in front, to form the
lateral boundaries of the posterior nares, the palate-bones
become broader posteriorly, approach one another, and are
either attached to, or anchylosed with, the posterior extremity
of the so-called "vomer." Their posterior extremities are
provided with facets for articulation with the bar-like ptery-
goids, which extend from them, outwards and backwards, to
articulate with the quadrate bone on each side. The pterygoids
of certain birds have also secondary connections ; they
articulate with processes which project from the post-sphenoidal
centrum in some part of its extent ; and on which their shafts
glide, rotate, or vibrate.
The reciprocal relations of the so-called "vomer," the
palatines, and pterygoids of the bird, are extremely interesting
and important. At present, I can only direct attention to
those relations which bear upon my subject. When the
palate-bones are greatly developed, the "vorner" diminishes.
160 ON THE MORPHOLOGICAL CONSTITUTION OF
When, again, the "vomer" is much developed, the palatines
are in an atrophied condition. The pterygoids present phases
of development dependent on the variations of the palatines
and pterygoids. The two extremes may be observed in the
parrots and the struthious birds. In the former, the palatines
are enormously developed, while the "vomer" has disap-
peared. In the latter, the " vomer " is greatly elongated and
developed, while the palatines present the relation, and ex-
hibit the form, of the " transverse" or " adgustal " bones of
the reptile.
The Palatal Arch and the Pterygoids in Reptiles and
Amphibians. The three bones on each side, which form the
palatal system of the ordinary lizard, present the same
relations, and almost the same form, as the " vomer," palatines,
and pterygoids of the struthious birds. The pterygoids are
in every respect similar. The " transverse bones " of the
lizard are also, in relations and almost in form, like the
palatines of these birds. The so-called " palatals" of the
lizard, while they exhibit all those relations to the " transverse"
and pterygoids, which the "vomer" of the bird presents,
differ from that double bone in this respect, that although in
contact at the mesial line, they are comparatively so much
broader, occupying so much of the comparatively narrow
palatal space that they touch the maxillaries by their anterior
external angles. They bound, therefore, the internal nares
posteriorly ; but, like the so-called vomer in the bird, separate
them from one another, passing forward like that double bone
to the ethmoidal neurapophyseal plates, which constitute the
so-called " vomer " of the lizard. In the monitors, these so-
called " palatines," like the pterygoids, are evidently separated
in the middle line, and forced backwards along the inner
margin of the maxillary towards the transverse bones, by the
development and elongation of the ethmoidal neurapophyseal
elements. In the crocodiles, again, the full development of
THE SKELETON OF THE VERTEBRATE HEAD. 161
maxillary palatal plates, and more especially of the ethmoidal
neurapophyses, has forced backwards and towards the middle
line, not only the bone called " palatal " in the lizard, but also
the pterygoids ; and as the latter also exhibit that remarkable
tubular development, various phases of which are perceptible
in the Chelonians, Birds, and Mammalia, the former again
presents the ornithic vomerine aspect.
In the Ophidia the two halves of the palatal system are
widely separated at the middle line. The so-called "palatals,"
elongated forwards into the ethmoidal region, articulated by
ascending processes to the pre-sphenoid, slightly attached
externally to the maxillaries, as in the lizards, bound as in
these reptiles, the nostrils posteriorly, but do not separate
them mesially.
In the frog, the so-called " palatals " extend transversely
outwards from the " os en ceinture " to the maxillaries, being
also connected at their outer extremities with the pterygoids.
The latter are articulated posteriorly to the post-sphenoid and
to the quadrate bone. The " os transversum " has disappeared
at the junction of the so-called palatal, pterygoid, and maxillary.
The modifications presented by these bones in reptiles and
Amphibia are much too numerous to be followed in detail at
present. I have therefore selected those which are essential
for the elucidation of my subject ; and shall sum up the con-
clusions I draw from them, by a comparison of them with the
corresponding elements in chelonians.
The chelonians, we are told, have no "transverse bone."
They are distinguished in this respect from all the other
reptiles. But if we examine the skull of a tortoise, we shall
find all the elements which enter into the formation of the
palatine aspect in that of the crocodile. In front are the
intermaxillaries, immediately behind which, in the median
line, is the double bony plate, which is usually described and
figured as the fore part of the so-called " vomer," but to which
If
162 ON THE MORPHOLOGICAL CONSTITUTION OF
I have already directed attention as the combined ethmoidal
neurapophyseal elements. In the turtles the maxillaries meet
across the palatal vault in front of the united ethmoidal
neurapophyses, so that the latter are pushed backwards, and
are in contact laterally with the palatals in the vault of the
palate ; while in the tortoise the latter want entirely the
palatal processes, consisting, as Cuvier expressed it, only of
their upper portions, and extending outwards on each side from
the outer margins of the so-called " vomer," and of the ptery-
goids, to the inner margins of the maxillaries. Now, let the base
of the skull of a tortoise, a turtle, and a crocodile, be examined
side by side. In all three we shall find the intermaxillaries
in front. The maxillaries, although they do not meet across
the palate of the tortoise, do so in that of the turtle, and thus,
as in the crocodile, bound posteriorly the intermaxillary
segment of the palate. The transverse union of the maxillaries,
in the turtle and crocodile, pushes back the ethmoidal
neurapophyses (which are in contact with the intermaxillaries
in the tortoise), but to such an extent in the crocodile that
the ethmoidal neurapophyses, also themselves much elongated,
carry back the pterygoids, so that the latter almost entirely
conceal the post-sphenoidal centrum. The outer margins of
the pterygoids, already curved downwards in the tortoise and
turtle, pass downwards and inwards in the crocodile, so as to
meet again in the mesial line of the palatal vault. The bony
septum of the pterygo-ethmoidal portion of the nostrils of the
crocodile is at the same time seen to be the result of the
extension downwards in the mesial plane of the middle ridge
of the so-called " vomer " of the tortoise or turtle, and of the
connection of the anterior part of that double bone with the
ethmoidal neurapophyses. It will thus be observed, that if
the maxillaries of the tortoise were united across the palate,
in front of its ethmoidal neurapophyses, to a considerable
extent backwards ; if the ethmoidal neurapophyses were also
THE SKELETON OF THE VERTEBRATE HEAD. 163
elongated in the same direction ; and if the outer margins of
the pterygoids, below the palatines, were to meet in the mesial
line, the latter would be forced backwards and outwards ; so
that, still retaining their connections with the pterygoids and
maxillaries, but leaving those with the " vomer " in front and
internally to abut against the malar behind and externally
the palatal aspect of the skull of the tortoise would present
the arrangement of the corresponding region in that of the
crocodile, the palate-bones assuming the form and relations
of " transverse bones."
If to the skulls of the tortoise, turtle, and crocodile, those
of a serpent, a lizard, a frog, and an ostrich be added, it
will be observed that the palate-bones have disappeared in
the frog ; that they have assumed the form and relations of
" transverse bones " in the lizard, crocodile, and serpent ,
that they are essentially " transverse bones " in the struthious
bird, while in the tortoise, but especially in the turtle, they
present the mammalian (?) character and form. It will also be
observed, that the bones in the turtle, tortoise, crocodile, and
bird, hitherto denominated "vomer," are the same bones
which in the frog, lizard, and serpent, are named "palatals,"
the term " vomer " being applied in these animals to those two
bones collectively, which are situated under the ethmoidal
portion of the skull. It will also be noted that the bones
called "vomer" in the* crocodile and bird, and the bones
called " palatals " in the frog, lizard, and serpent, are related
to the others, along with which they have been examined,
exactly as the " bones of Bertin," in the human cranium, are to
the palate-bones and pterygoids.
The Pre-sphenoidal Hcemal Arch and Hcemactinapophysis
of tlie Fish. In the osseous fish a fibrous membrane extends
outwards and downwards on each side from the suborbital bar-
In the annotated copy the words turtle and tortoise, which appeared in
the original memoir, were deleted. (Eos. )
164 ON THE MORPHOLOGICAL CONSTITUTION OF
like portion of the basis of the cranium. In most fishes there
will be found in this membrane, where it passes off from the
pre-sphenoidal portion of the cranium, a more or less elongated
scale-like bone on each side. This is the " pterygo'idien
interne" of Cuvier, the "herisseal" of St. Hilaire, the "ento-
pterygoid" of Professor Owen. The palate-bone, connected
by the same fibrous membrane to the outer margin of the
ento-pterygoid, extends forwards to the side of the so-called
" vomer," or to the ethmoidal centrum and neurapophysis, to
which, as also to the maxillary and intermaxillary, it is
variously attached directly and indirectly. The corresponding
actinapophyseal element or pterygoid in the fish is firmly
connected in front to the palate-bone, and less intimately to
the ento-pterygoid, and, extending backwards, downwards, and
outwards, abuts against the anterior margin of the " hypo-
tympanic " and " pre-tympanic " bones, as the pterygoid of the
bird and reptile does against the so-called "quadrate," or
" tympanic " bone. If, then, the basal aspect of the cranium
of the osseous fish is placed in series with those of the bird,
lizard, serpent, tortoise, and frog, it will be observed, that
while its palatals and pterygoids may be at once associated
with the corresponding bones, as already determined, in the
bird and reptile, the ento-pterygoid of the fish presents all
the relation of the double bone, usually called " vomer " in the
bird ; of the posterior or horizontal portion of the bone called
" vomer " in the tortoise ; and of the bones called " palatals "
in the lizard, serpent, and frog. It will also be observed, that
while the toothed bone, called " vomer " in the fish, has, from
a catacentric change, disappeared from the under aspect of the
cranium in the bird, reptile, and batrachian, the two bones,
called in the fish " pre-frontals " its ethmoidal neurapophyses
present the same relations to its ento-pterygoids as the
ethmoidal neurapophyses of the bird to its so called " vomer,"
and as those of the tortoise to the posterior portion of its so-
THE SKELETON OF THE VERTEBKATE HEAD. 165
called " vomer," and as those of the lizard, serpent, and frog to
the bones hitherto called " palatal " in these three forms. I
therefore apply provisionally the term ento-pterygoid to the
so-called " vomer " of the bird, to the posterior part of the so-
called " vomer " of the chelonian, to the corresponding bony
piece in the crocodiles, to the so-called "palatals" of the
ophidian, lacertian, and batrachian, to the " bones of Bertin,"
and their representatives in the mammal.
The Constitution of the Nasal Fossae, and the Relative Posi-
tions of the External and Internal Nares. The details necessary
for the morphological examination of the rhinal, vomerine,
ethmoidal, and pre-sphenoidal sclerotomes, have involved a
number of facts connected with the varied constitution of the
nasal fossae in the different vertebrate forms. As, however,
the constitution of these fossae has important bearings on the
morphology of the entire cranium, I shall briefly direct atten-
tion to the subject.
The only perfect form of nasal fossae is that presented by
the mammal. They consist of the entire neuro-haemal cavities
of the rhinal and vomerine, combined with the haemal cavities
of the ethmoidal and pre-sphenoidal sclerotomes. That portion
of the combined nasal fossae which consists of the cavities of
the rhinal and vomerine sclerotomes, is divided in the mesial
plane by the centrums of those sclerotomes ; while the
dependent portion of the ethmoidal centrum, and the posterior
portion of the vomerine centrum, divide in the same manner
that part of the combined fossae which consists of the haemal
cavities of the ethmoidal and pre-sphenoidal sclerotomes. The
mammalian nasal fossae are therefore bounded in front by the
walls of the neuro-haemal chambers of two catacentric sclero-
tomes ; and posteriorly by the catacentrically divided haemal
chambers of a demicatacentric and diacentric sclerotome.
As the haemal portions of the cephalic somatomes are
separated from one another in their early embryo condition by
166 ON THE MORPHOLOGICAL CONSTITUTION OF
metasomatomic clefts, we may expect to find traces of these
clefts in the walls of the adult nasal fossae.
The first or anterior pair of metasomatomic clefts of the
embryo head, that is the clefts between the rhinal and inter-
maxillary lobe of the " median frontal process," are retained
in the adult as the external nares. These openings in the
non-proboscidian mammal, are situated therefore between the
ali-nasal cartilages and the intermaxillary bones. In the pro-
boscidian mammals, they are probably situated between the
ultimate and penultimate, or, at least, between two of the
distal somatomes of the proboscis.
The second pair of metasomatomic clefts, situated between
the external angles of the median frontal process and the
lateral frontal processes, may disappear entirely in the course
of development ; but they occasionally remain under the form
of Stenson's ducts, which pass obliquely through the so-called
" incisive spaces," or " foramina," from the mouth to the nasal
fossae, between the intermaxillaries and maxillaries. The
mucous walls of the canals of Stenson are supported by
cartilaginous tubular folds, which are continuous superiorly
with cartilaginous lamina, which, passing off laterally from
the lower margin of the nasal septum and vomer, cover more
or less of the floor of the nasal fossae, upper part of the incisive
fissures, and spaces between the intermaxillaries and maxilla-
ries. The " organs " or " sacs of Jacobson/' supplied by the
olfactory and fifth nerves, lined by glandular integument,
sheathed by a continuation of the cartilaginous laminae
already alluded to, and opening into the canals of Stenson,
when these are present, are, whatever their function may be,
morphologically connected with the second pair of meta-
somatomic clefts.
The next pair of metasomatomic clefts, situated between
the lateral frontal processes and the so-called " superior
maxillary " deflection of the " first visceral lamina/' con-
THE SKELETON OF THE VERTEBRATE HEAD. 16*7
timie pervious in all the Mammalia except the Cetacea. The
lachrymal canals which connect the anterior pouches of the
conjunctive with the nasal fossse, consist of the persistent
upper portions of these clefts. Their outer or lower portions
are obliterated, but the corresponding inter-scleratomic space,
much dilated, constitutes that part of the orbit formed by
elements of the ethmoidal and pre-sphenoidal sclerotomes,
while the spheno-palatine and posterior palatine foramina and
fissures are also enclosed portions of the space between these
two sclerotomes, retained for the passage of vessels and nerves.
The posterior nares are not meta-somatomic openings, they t
are merely the communications between the catacentric hsemal
space of the pre-sphenoidal, and the corresponding but un-
divided hsemal spaces of the succeeding somatomes.
The mouth is the persistent and developed form of the
great cleft between the pre- and post-sphenoidal somatomes.
It is situated therefore morphologically in the same transverse
plane as the posterior nares. Its fundamental or morpho-
logical relations are retained and represented by the posterior
isthmus of the fauces. The buccal chamber is a vestibule
superadded to the alimentary tube, by the anterior elongation
of the lower jaw, and by the development of the floor of the
mouth and. of the tongue, with the consequent inclusion of
the vault of the palate ; so that the latter, instead of forming
the anterior portion of the haemal or sternal aspect of the head,
becomes apparently a portion of the wall of the visceral tube.
The complete development of the vomer, characteristic, as
already stated, of the mammalian head, is also a characteristic
feature of the nasal fossse in the mammal. As the centrum of
that sclerotome, of which the intermaxillaries are the hsema-
pophyses, it extends back from them to abut against the pre-
sphenoidal centrum, forming a beam which adds to the antero-
posterior strength of the entire arrangement, and which
supports the more feebly-developed ethmoidal and rhinal
168 ON THE MORPHOLOGICAL CONSTITUTION OF
portions of the nasal septum. All these relations of the
vomer are retained in the remarkably-modified nasal passages
and snout in the Cetacea.
The seat of the olfactory sense is limited to the upper part
of the ethmoidal portion of the nasal fossae. However com-
plex the arrangement of the ethmoidal turbinal laminae may
be, they invariably present the general character of folded
laminar neuractinapophyses, connected to their corresponding
neurapophyses, after the type of the cartilaginous sessile
olfactory cups in the plagiostomes.
As already stated, the so-called inferior turbinals consist
of an antero-posteriorly arranged series or system of mutually
abutting hsemactinapophyses, enclosed during development
within the nasal fossae. The inferior turbinal system is
peculiar to the mammal, and consists of elements which, in
developed forms of the system, are derived from, and attached
to, the rhinal, vomerine, and ethmoidal haemapophyses. The
palate-bone, or distal pre-sphenoidal haemapophysis, supports
the posterior extremity of the turbinal system, but I have not
had occasion to observe any turbinal element supplied by it.
As the rhinal sclerotome has disappeared in the bird, the
neuro-haemal chambers of the vomerine sclerotome become
closed in front, and the external nostrils are supplied by those
rnetasomatomic clefts between the vomerine and ethmoidal
sclerotomes, which in the mammal form the " incisive
foramina," the " canals of Stenson/' and the " organs of
Jacobson."
As the anterior nares are removed one somatome back in
the bird, so the posterior nares are removed one somatome for-
wards. They are situated between the maxillary and incom-
plete palatine arches, theento-pterygoids separating them, while
the palatines are on their outer sides. The posterior nares,
instead of being directed backwards in a plane at right angles
to the axis of the alimentary tube, open downwards in the
THE SKELETON OF THE VERTEBRATE HEAD. 169
plane of its upper wall. This direction of the posterior nares
is due to the following circumstances : 1. That the inter-
maxillaries, although- completing their arch below, are
principally developed upwards and backwards ; 2. That the
maxillaries, even when they meet partially across the middle
line, have the space which they enclose occupied by the
neurapophyses, centrum, and sense-capsules of their own
sclerotome in other words, they are in contact with the
central and neurapophyseal aspect of their own sclerotome ;
3. That the palatines do not form an arch at all, but lie in
the horizontal plane of the under surfaces of the centrums of
the cephalic sclerotomes behind them.
The bird, in fact, does not possess nasal fossae in the same
sense as the mammal that is, it does not present nasal
chambers, formed by the completed haemal arches of a certain
number of sclerotomes. Its nasal fossae consist only of the
catacentric-haemal or neuro-hsemal spaces of the vomerine
sclerotome, and of the combined neural and " sense-capsule "
spaces of the ethmoidal sclerotome, which occupy the space
enclosed by its haemal arch. They differ therefore from the
mammalian nasal fossae, not only in wanting rhinal compart-
ments, but also in the deficiency of ethmoidal and pre-
sphenoidal haemal spaces. The palate of the bird, instead of
being, like that of the mammal, situated in a plane inferior
and parallel to that in which the vertebral column lies (?), is in
the plane of the latter, like that of the fish. The palate of the
fish is in the horizontal plane of the vertebral column, because
its nasal fossae are absent, the constituent haemal arches being
all incomplete ; and because the cavities of its olfactory
capsules open externally. The palate of the bird is in the
horizontal plane of the vertebral column for reasons already
stated, and also because the olfactory capsules, instead of
being situated external to the cavities of their sclerotome, as
in the fish, or in its haemal cavity, as in the mammal, have
170 ON THE MOEPHOLOGICAL CONSTITUTION OF
become involved in, or have taken the place of, its neural
chamber, and have therefore their inner orifices or posterior
nares directed downwards, on the central aspect.
The mode in which the walls and cavities of the olfactory
capsules of the bird become involved or lost in its ethmoidal
neural chamber and walls, may be morphologically conceived,
if the structure is compared with the corresponding segment
of the cranium of a ray. The cranium of the plagiostome is
modelled on the form of the "primordial cranium" of the
mammal and bird. The laterally projecting sessile cartila-
ginous olfactory cups communicate each by a wide orifice with
the cranial cavity. If the orifices be conceived as much en-
larged, and the walls of the capsules as withdrawn into, or
becoming continuous with, those of the cranium ; or if the
latter be conceived as disappearing, while the former take
their places, the general arrangement of the ethmoidal section
of the persistent " primordial cranium " of the ray will be
seen to be similar to that sclerotome in the bird's skull which
retains most of the primordial character. The development
of the imperfect maxillaries in contact with the lower aspect of
the slightly-ossified inferior wall of the combined capsular
and neural mass, and the formation of the ethmoido-frontals
in the perichondrium which covers its upper surface, would
reduce the entire arrangement to the type of the correspond-
ing parts in the bird.
By a similar process, the sessile cartilaginous auditory
capsules of the cyclostome may be conceived to become buried
in the temporal portions of the cranial wall in the plagiostome,
while in the osseous fish, after the primordial cranium has
become enveloped in the bony plates, which are formed in its
substance and in its fibrous covering, the auditory capsules
pass into the cranial cavity, having been enclosed by the
neurapophyseal and meta-neurapophyseal bony pieces of their
own and neighbouring sclerotomes.
THE SKELETON OF THE VERTEBRATE HEAD. 171
The external nostrils of the lacertian, ophidian, and am-
phibian, are situated, as in the bird, between the vomerine
and ethmoidal sclerotomes ; the intermaxillaries being closed
in front and below. The so-called nasal fossae in these verte-
brate forms are also, as in the bird, merely olfactory chambers,
occupying the neural space of the ethmoidal sclerotome. The
posterior nares, too, open as in the bird, between the eth-
moidal and pre-sphenoidal sclerotomes, but with the follow-
ing subordinate differences : In the lizard they are separated
by the anterior extremities of the ento-pterygoids, and are
bounded behind by the maxillary processes of these bones,
and externally by the rnaxillaries themselves. In the ophidian
they are separated by the free margin of the ethmoidal cata-
centric plates ; anteriorly by the posterior margins of the eth-
moidal neurapophyses, externally by the anterior projecting
portions of the ento-pterygoids, and behind by the pre-
sphenoidal attachments of the latter. In the frog they open
between the ethmoidal neurapophyses ("vomer"), the ento-
pterygoids (" palatals "), and the maxillaries.
We again approach the mammalian type of nasal fossse,
through the tortoises, turtles, and crocodiles.
It has been already stated that the anterior nostrils of the
Chelonian appear to possess more of the ornithic than mam-
malian conformation. The primordial cartilaginous lining of
the olfactory fossse projects in some turtles through the an-
terior nasal opening of the cranium in the form of a double
proboscis. The posterior nares in the tortoises are separated
by the combined ento-pterygoids (upper and back part of the
" vomer"), and are bounded by the maxillaries and the pala-
tines, the latter remaining open or ununited across the vault
of the palate. In the turtles, the vault of the palate and the
posterior nares present more of the mammalian aspect,
although still formed essentially on the type of the corre-
sponding parts in the bird. This is effected by the ethmoidal
172 ON THE MORPHOLOGICAL CONSTITUTION OF
neurapophyseal plates (palatal plate of the " vomer") which
lie somewhat above the level of the vault of the palate in the
tortoises, passing down into, and forming an area of it in the
turtles, extending from its posterior margin half-way, or quite
up to the intermaxillary palate-plates. In the latter arrange-
ment the ethmoidal area is hexagonal, and separates the
palatal plates of the maxillaries from one another. In the
former it is pentagonal ; and the palatal maxillary plates
meet in the mesial line in front of it. The palatal plates of
the palatines are more or less developed in the turtles ; and
many approach one another at the free margin of the vault,
but are always separated by the posterior or free margin of
the ethmoidal area.
The arrangement of the vault of the palate in the turtles,
and the peculiar chelonian configuration of the pterygoids,
lead to the very remarkable combination of ornithic and
mammalian structure presented by the nasal fossae and palatal
vault of the crocodiles. The mammalian characteristics are
the full development of the intermaxillary and nasal bones,
with the extensive, although cartilaginous, vomer. The
vomerine sclerotome of the crocodile is not closed anteriorly
as in all the other lacertians, in the ophidians, amphibians,
and birds, but presents a completely perforated catacentric
arrangement. This complete form of the vomerine necessitates
a rhinal sclerotome, which, accordingly, feebly represented in
the crocodiles and alligators, appears to be more fully de-
veloped in the gavials. The extensive and complete croco-
dilian palatal vault is only apparently mammalian, it is par-
tially ornithic or chelonian in its constitution. As in the
mammal, the anterior extremity of the vault is formed by the
pair of fully formed palatal inter-maxillary plates. Except
in the alligators, in which there is a slight intrusion of the
ento-pterygoids, the palatal plates of the maxillaries, meeting
along the mesial line, form the second and most extensive
THE SKELETON OF THE VERTEBRATE HEAD. 1*73
area of the palatal vault. The next area of the vault consists,
as in the turtles, of the ethmoidal neurapophyses (the so-
called "palatals"), united along the mesial line, and much
elongated backwards. The posterior margin of the combined
ethmoidal neurapophyses of the turtle forms the central part
of the free margin of the palate ; but the completion in the
crocodile of the deflected outer margin and central ridge of
the pterygoids into a double tube, or pterygoidean prolonga-
tion backwards of the nasal fossae, produces a corresponding
elongation of the palatal vault, which accordingly presents,
behind its ethmoidal, an extensive and broad pterygoidean
area, which thus completes the vault behind, as in certain
Cetacea and Edentata. The great elongation backwards of
the combined maxillary palatal plates, the corresponding
elongation of the combined ethmoidal neurapophyses, and the
great breadth of the pterygoidean area, have displaced the
palate-bones so far backwards and outwards, that, separated
from the ento-pterygoids and the ethmoidal neurapophyses by
a wide chasm, but retaining their connections with the maxil-
laries and pterygoids, and coming into contact with the malar,
they are, in fact, extruded from the walls of the nasal fossse,
and from the palatal vault, and, thus disguised, have been
hitherto known only as " transverse bones," " adgustal bones,"
" pterygoides externes," " ecto-pterygoids."
The Nasal Passage of the Cyclostomous Fishes. The cyclo-
stomes differ from all other fishes in possessing a tubular
passage, which, opening externally above the oral disk, passes
backwards to the combined olfactory capsules, and behind
which it terminates in a cul-de-sac in the lamprey, but in the
myxine and bdellostoma communicates with the alimentary
and respiratory tract.
The form and arrangement of the cartilages, which enter
into the formation of the walls of this tubular passage, have
been figured and minutely described in the classical memoirs
174 ON THE MORPHOLOGICAL CONSTITUTION OF
of Joli. Miiller, on the " Cyclostomous Fishes." It becomes
a point of much interest to ascertain the morphological cha-
racter of this tubular passage, and to determine the morpho-
logical relations of its cartilaginous elements.
The olfactory capsules of the myxine, bdellostoma, and
lamprey, are completely fused into one another at the mesial
plane, so as to form a single chamber, situated immediately
in front of, and in a line with, the cranial cavity. The
common olfactory chamber communicates with the cranial
cavity by two orifices perforated in the fibro-cartilaginous
transverse septum, for the passage forwards of the olfactory
nerves. The olfactory chamber opens below into the naso-
pharyngeal passage. In the lamprey this passage is mem-
branous throughout, the portion in front of the olfactory
chamber lying above the posterior superior oral shield ; its
posterior portion passing back between the base of the
cranium and the central part of the palatal cartilage, ter-
minates in a cul-de-sac at its pharyngeal extremity. In the
myxine and bdellostoma the posterior portion of the passage
is a membranous canal situated between the base of the
cranium and the mesial palatal cartilage, and opens posteriorly
into the pharynx. That portion of the naso-pharyngeal
passage in front of the olfactory chamber is supported above
and laterally by a series of ten cartilaginous rings, incom-
plete below the entire arrangement closely resembling a
mammalian trachea. The membranous floor of this part of
the passage is supported by the anterior portion of the central,
and the transverse junction of the lateral palatal cartilages,
and in front by the mesial and transverse superior oral
cartilages.
The morphological constitution of this remarkable nasal
skeleton appears to be similar to that of the nasal fossae of
the higher Vertebrata. The olfactory capsules have passed
inwards, as in the bird and reptile, so that, instead of pro-
THE SKELETON OF THE VERTEBRATE HEAD. 1*75
jecting from the sides of the cranium, like the auditory
capsules, they occupy the space of the corresponding cranial
segment. The incomplete cartilaginous rings of the nasal
tube, viewed in their relations to the cranium and conjoined
olfactory capsules, are in the position of a superadded series
of neural arches, similar to the neural portions of the rhinal
and vomerine mammalian sclerotomes, destitute, however, of
centrums, but supported below by the peculiarly-developed
palatine and maxillary elements which have passed forward
beneath them. The entire arrangement presents the general
characters, or is developed on the plan of the nasal fossae of
the reptile, bird, and mammal, with the additional peculiarity
of an increase in the number of constituent segments, similar
to that which apparently exists in the proboscidian mammals.
POST-STOMAL CEPHALIC SCLEROTOMES. Their Central and
Neural Elements. As the discrimination of the constituent
central and neural elements of the three post-stomal segments
of the skull demands a constant reference from the one seg-
ment to the other, I shall examine them together. Of these
three segments the post-sphenoidal, the temporal, and the
occipital the second has not hitherto been recognised except
by Carus, whose system includes a temporal intervertebra.
My attention was directed to the temporal segment of the
cranium by the remarkable indications of it presented by the
human skull. The human occipital bone, in addition to that
upper angular portion of its squamous plate, which presents
the relations of the interparietal, exhibits all the character-
istics of a vertebral centrum, in combination with neura- and
meta-neurapophyses. The inferior articular processes of this
cranial segment are largely developed, in relation to the atlas.
But it has not been hitherto noted, that the so-called jugular
processes are in fact its upper or anterior pair of articular
processes ; and that, consequently, the jugular processes on
the posterior margins of the petrosal portions of the temporals
176 ON THE MORPHOLOGICAL CONSTITUTION OF
must be the zygopopliyses of the succeeding cranial segment.
These occipital and temporal jugular articular processes, like
the corresponding processes in the column below, present
distinct cartilaginous articular facets, and are contiguous to
the "foramina lacera posteriora" or " intervertebral fora-
mina," formed by the conjunction of the temporal and
occipital jugular fossae, and which transmit, as in the spine,
vessels and nerves. But the petrous portion of the human
temporal bone has, in addition, a pair of distinct pro-zygo-
pophyses. They are situated on the anterior margins of the
petrous portions, where these margins form the angles with
the squamous portions, in which are situated the openings of
the Eustachian tubes. The articular surfaces of these pro-
cesses are perpendicularly striated, and are applied against
corresponding surfaces of the so-called styloid processes of
the sphenoid at the posterior angles of its great wings. These
" styloid processes " are therefore the zygopophyses of the
post-sphenoidal sclerotome. The pro-zygopophyses of the
post-sphenoidal and the zygopophyses of the pre-sphenoidal
may be observed at the fore part of the pterygo-palatine groove
in the foetal bone, but are more remarkably developed in the
young ruminant ; in which also may be observed the zygo-
pophyseal connection of the pre-sphenoidal with the ethmoidal
neurapophyses.
We have, therefore, in these zygopophyseal connections
distinct evidence of five cranial segments an ethmoidal, pre-
sphenoidal, post-sphenoidal, temporal, and occipital in addi-
tion to the vomerine and rhinal.
For the further development of this subject, the cranium
of a cyprinoid fish should next be selected. If the lateral
wall of the cranium be examined, either from the external or
mesial aspect, five serially-arranged neurapophyseal plates
will be recognised, connected to one another by four distinct
zygopophyseal articulations. These plates are, from before
THE SKELETON OF THE VERTEBRATE HEAD. 177
backwards, the so-called " pre-frontal," the " cranial ethmoid,"
the " orbito-sphenoid " of Owen, the " ali-sphenoid " of Owen,
and the lateral occipital. I have already stated the grounds
on which I believe we must look upon the " pre-frontals " of
the fish as the neurapophyses of the ethmoidal, and the
" cranial ethmoid," as the combined neurapophyses of the pre-
sphenoidal neural arches. If so, then the succeeding plate
must be the " ali-sphenoid," and not the " orbito-sphenoid/' as
Professor Owen considers it to be ; and therefore, as there
has never been a question regarding the lateral occipital, the
plate interposed between the latter and the former, as it has
all the characters of a neurapophysis, indicates the existence
of a cranial segment between the post-sphenoidal and oc-
cipital. I shall not at present allude to the various opinions
entertained regarding this plate, but shall merely distinguish
it as the inferior temporal neurapophysis.
Proceeding now to the consideration of the centrums cor-
responding to this series of neurapophyses, it must be ob-
served that in no osseous fish in any stage of development have
more than three osseous pieces been observed in the basis of
the cranium from the so-called " vomer" to the " basi-occipital"
included. The assumed " connation " of the centrums of the
pre- and post-sphenoids, as held by Professor Owen, has at
present no support from embryology ; the missing centrum or
centrums must therefore be accounted for otherwise than by a
hypothetical division of the " basi-sphenoid." Professor Owen
appears, indeed, to a certain extent to admit this, for in
certain fishes he considers the symmetrical Y-shaped ossicle
marked in his diagrams 9 1 , and superimposed on the pre-
sphenoidal process of his basi-sphenoid, as the central part ;
while that process itself he holds to be the capsular portion
of the ossified notochord.
That mutual elongation and overlapping of the cranial
centrums formerly alluded to is strongly marked in fishes, the
N
178 ON THE MORPHOLOGICAL CONSTITUTION OF
sphenoidal centrum being dovetailed into and elongated beneath
the occipital behind, and above the ethmoidal (" vomer ") in
front. The manner in which the anterior elongated portion
of the post-sphenoidal centrum of the bird elevates and carries
on its upper surface the compressed pre-sphenoidal centrum
has already been stated ; and I must again observe that it
appears to me that the pre-sphenoidal centrum exists in certain
fishes only in the form of a bar of cartilage a portion of the
"primordial cranium" situated on the upper surface of the
anterior prolongation of the post-sphenoidal centrum, and
terminating on the upper surface of the ethmoidal centrum or
so-called " vomer," and that in fishes with an " ossified orbital
septum " or " cranial ethmoid," it is to be recognised in the
half- ossified cartilaginous mass which unites the right and left
plates of that " septum," and which have been already indi-
cated as its corresponding neurapophyses. The pre-sphenoidal
is an undeveloped centrum in the fish, retaining more or less
of its w primordial" texture and form, and elevated, therefore,
above, or carried inwards, so as to be covered by the fully-
developed ethmoidal and post-sphenoidal centrums.
I am acquainted with no example of a fully-developed
temporal centrum. It is represented in the "primordial
cranium" by the quadrilateral cartilaginous plate, bounded
laterally by the ear-capsules, behind by the portion corre-
sponding to the cartilaginous lateral occipitals, and in front by
the part in which the post-sphenoidal centrum first appears.
In all vertebrate animals this portion of the basis of the
primordial cranium is of great comparative extent, and is
encroached upon by the advancing ossification of the occipital
and post-sphenoidal centrums in modes which vary in the
different vertebrate forms. In mammals, the occipital advances
into it at the expense of the post-sphenoidal centrum. In
birds and fishes the post-sphenoidal passes more backwards.
In the reptiles the two centrums appear to share it equally.
THE SKELETON OF THE VERTEBRATE HEAD. 179
In all the forms, I believe that traces of the intermediate or
temporal centrum may be detected, either in the cartilaginous
or osseous condition. In fishes, more or less of the primordial
cartilage remains above the junction of the occipital centrum,
post-sphenoidal centrum, and temporal neurapophyses (" petro-
sals"), and covered more or less internally, or towards the
cranial cavity, by the internal prolongations of the occipital
centrum, and of the temporal and post-sphenoidal neurapo-
physes. The peculiar canal for the muscles of the orbit
existing in certain fishes, and which is roofed over principally
by the " petrosals," or temporal neurapophyses, appears to be
hollowed out principally in the primordial temporal centrum,
and to be lined by its constituent cartilage. The peculiar Y-
shaped bone met with in the pike, perch, and salmon, marked
9 1 by Professor Owen, and * by Hallman, and considered by
the former as that portion of the pre-sphenoidal centrum which
results from the ossification of the corresponding central por-
tion of the notochord, appears to me to be a central element,
but referable rather to the post-sphenoidal or temporal than
to the pre-sphenoidal segment. For, in the first place, it may
be questioned whether the corda dorsalis of the fish reaches
the region of the pre-sphenoid ; and, in the second place, if I
am correct in my determination of the post-sphenoidal and
temporal neurapophyses of the fish, the two ascending limbs
of this bone abut against these latter elements, and are not at
all connected with the pre-sphenoidal neurapophyses. As,
moreover, these ascending limbs of the bone in question are
more intimately connected with the bones which Professor
Owen considers to be the ali-sphenoids, but which I must hold
to be the inferior temporal neurapophyses, I am inclined to
conceive it an ossified portion of the temporal centrum.
With regard to the bone termed by Hallman os innomi-
natum, which is small but well marked in the carp, and larger
in the perch, and which Professor Owen considers to be the
180 ON THE MORPHOLOGICAL CONSTITUTION OF
petrosal, I quite agree with him. But while I do so, I make
a distinction between an ossified portion of the auditory
capsule and the bone which constitutes the corresponding
neurapophysis, in the same manner as I find myself compelled
to admit the independent existence of the ethmoidal neura-
pophysis and the olfactory capsules, whether fibrous, cartila-
ginous, or osseous, and the corresponding independent existence
of the variously-modified sclerotics and the orbito-sphenoids.
Proceeding now to the examination of the remaining
elements of the post-stomal neural arches in the fish, I would
observe that if we put aside those conceptions of the constitution
of the arches in question, derived from previous study of the
cranium of the mammal, the constitution of the corresponding
arches in the fish which naturally suggests itself is the
following :
1. Over the occipital centrum the lateral occipitals and the
external occipitals as two pairs of neurapophyses, and the
superior occipital as a single meta-neurapophysis.
2. Over the position of the temporal centrum, the bones
termed petrosals by the continental anatomists, but by Professor
Owen petrosals in the cod, and ali-sphenoids in the carp, and
over these the mastoids, these " petrosals " or " ali-sphenoids,"
along with the mastoids as two pairs of neurapophyses, and
the contiguous or separated bones usually termed " parietals,"
as a divided meta-neurapophysis.
3. Over the great basi-sphenoid, the bones termed by
Professor Owen orbito-sphenoids in the carp, and ali-sphenoids
in the cod, with the post-frontals as two pairs of neurapo-
physes, the meta-neurapophyses being absent.
Before making any statements in support of this view of
the constitution of the post-stomal neural arches in the
cranium of the osseous fish, I would direct attention to the
corresponding parts in the other Vertebrata from the same
point of view.
THE SKELETON OF THE VERTEBRATE HEAD. 181
In the bird, the occipital neural arch wants the ex-occipitals.
The temporal arch possesses no centrum, but the petrosals,
mastoids, and parietals are placed one over the other as two
pairs of neurapophyses and a divided meta-neurapophysis.
The post-sphenoidal centrum is surmounted by the post-
sphenoidal wings and the feebly-developed post-frontals as
two pairs of neurapophyses, while the meta-neurapophysis is
deficient.
In the crocodiles, the occipital arch, as in the birds, has
lost the upper pair of neurapophyses. The temporal centrum
is not developed, but the two pairs of neurapophyses, and an
undivided meta-neurapophysis the petrosals (ali-sphenoids
of Owen), mastoids, and so-called parietal form a continuous
arch. The post-sphenoidal centrum is again found to carry
two pairs of neurapophyses, the great sphenoidal wings (orbito-
sphenoids of Owen), and the post-frontals. The meta-
neurapophysis is missing.
In the chelonians, the occipital arch consists of one pair
of neurapophyses and a meta-neurapophysis surmounting a
centrum. The temporal centrum is not developed. The
inferior pair of neurapophyses, the so-called ex-occipitals, abut
externally against the mastoids, and are thus connected with
the largely-developed so-called "parietals." These "parietals"
not only form a large part of the cranial and temporal vaults,
but send down laminae to rest on the pterygoids, and thus
enter into the formation of the lateral walls of the cranial
cavity in front of the post-sphenoidal wings. Above the post-
sphenoidal centrum, the post-sphenoidal wings and the post-
frontals rise in connection with one another as two pairs of
neurapophyses, but the meta-neurapophysis is again wanting.
In the ophidians, the occipital centrum is again surmounted
by one pair of neurapophyses and a meta-neurapophysis. The
temporal centrum has disappeared behind the basi-sphenoid ;
but the well-developed so-called " petrosals," the ali-sphenoids
182 ON THE MORPHOLOGICAL CONSTITUTION OF
of Professor Owen, are surmounted by the elongated and
nearly extruded mastoids ; while the single meta-neurapophy-
sis, the undivided " parietal," is so largely developed, that,
passing down as in the chelonian to the basis of the cranium,
it rests upon the post-sphenoidal centrum over a great extent
in front of its own neurapophyses, so as altogether to
obliterate the post-sphenoidal wing. The post-sphenoidal
centrum is there cut off from the post-frontals, which consti-
tute the only remaining elements of its neural arch.
In the lacertians, the occipital centrum, with its pair of
neurapophyses and single neurapophysis, is followed by a
temporal arch, without a centrum, but with two pairs of neura-
pophyses, "petrosals," and mastoids, and an undivided meta-
neurapophysis or "parietal," generally single in front, but
projecting backwards, with the mastoids on each side behind.
The post-sphenoidal centrum is not surmounted by ali-sphe-
noids, except the parietal columella represents these elements.
The post-frontals again appear ; but without a corresponding
meta-neurapophysis.
In the frogs, the occipital centrum and the corresponding
meta-neurapophyses have disappeared ; a single pair of neura-
pophyses constituting the sole osseous elements of the arch.
The temporal centrum appears in the primordial cartilage,
which extends across on the upper surface of the posterior
part of the much-elongated " basi-sphenoid," and between the
cartilaginous auditory capsules. The latter are intimately
connected to the inferior temporal neurapophyses, the ali-
sphenoids of Professor Owen, with which feebly-developed
mastoids or superior neurapophyses are conjoined ; the whole
being surmounted by the greatly-developed antero-posteriorly
elongated so-called "parietals," which dip down slightly at
their margins, in front of the temporal region towards the
"basi-sphenoid," as in the chelonians and ophidians. The
portions of the post-sphenoidal wings and the post-frontals are
THE SKELETON OF THE VERTEBRATE HEAD. 183
occupied by fibrous texture ; the " basi-sphenoid" or post-
sphenoidal centrum extending forwards below ; and the " pari-
etals" taking the place of the deficient meta-neurapophyses.
The preceding view of the arrangement of the centrums
and neural arches of the post-stomal sclerotomes of the lower
forms of cranium, is that which would appear naturally to
suggest itself to a mind uninfluenced by the arrangement of
the corresponding region of the mammalian skull. It is
assumed throughout that there are more or less complete carti-
laginous or osseous auditory capsules in addition to correspond-
ing neurapophyses ; and that these neurapophyses are not
post-sphenoidal but temporal, as evinced by their zygopophy-
seal connections in the human cranium. No reference has
been made to the relations of the contested " petrosals" and
ali-sphenoids" to the fifth nerve, because, while the funda-
mental relation of that nerve to the post-sphenoidal sclerotome
is admitted, the divisions of the nerve exhibit the same
tendency to vary in their points of exit, as is presented by the
other cerebral nerves ; moving backwards more or less across
the corresponding neurapophyses, and notching or perforating
the neurapophyses behind. In fact, until a more minute
investigation of the development of the cranium in its relations
to the cerebral nerves has afforded some explanation of the
varied relations of these parts in the series, we cannot, in
my opinion, attach much weight to the determination of a
" petrosal" or an " ali-sphenoid" by means of their relations
to the trigeminal nerve.
Proceeding now to the examination of the post-stomal
centrums and neural arches of the mammalian cranium, let
the human skull be selected for examination. The occipital
centrum is surmounted by a pair of neurapophyses and a
double meta-neurapophysis. But again, surmounting the
meta-neurapophyses there is a double piece, which occasion-
ally remains permanently separate from the " occipital bone."
184 ON THE MORPHOLOGICAL CONSTITUTION OF
This double piece, or pair of bones, presents the relations of
the interparietal bones in lower Mammalia. They may extend
laterally to join the " mastoids," or they may be connected to
the latter by a more or less continuous chain of " triquetral
bones" in the line of the lambdoidal suture.
The zygopophyseal attachments of the " petrous portions
of the temporal bone " indicate these masses to be neurapo-
physes enveloping the ossified auditory capsules. Keeping
out of view the " squamous," " tympanic," and " styloid" por-
tions of the "temporal bones," the "mastoidal portions"
become early and intimately connected with the "petrous
portions." Commencing with the "petrous portions," as an
inferior pair of temporal neurapophyses, they are surmounted,
as in the lower Vertebrata, by the "mastoidal portions" as a
second pair of neurapophyses, while the arch is closed by the
doiible element which forms the upper angle of the " occipital
bone," as a meta-neurapophysis. There are well-marked indi-
cations of a temporal centrum in the human cranium. The
irregularly-truncated apices of the " petrous portions," directed
obliquely forwards and inwards, are continuous, by means of
the fibro-cartilaginous remains of the basis of the " primordial
cranium," which occupy the "foramina lacera media," with
the inclined plate of bone which, in the plane of the " basilar
process of the occipital" or occipital centrum, forms the back
part of the " body of the sphenoid," including the " posterior
clinoid processes." This plate of bone is frequently surrounded
by a deep groove, the posterior part of which lodges the
" transverse venous sinus," and I have seen it nearly detached.
The feebly-developed post-frontals in the bird have dis-
appeared in the mammal, so that the post-sphenoidal centrum
is surmounted by the " all-sphenoids," as a single pair of neura-
pophyses ; and by the enormously- expanded double meta-
neurapophysis in the human subject, or the less developed
form of parietals in the Mammalia generally.
THE SKELETON OF THE VERTEBRATE HEAD. 185
The fundamental facts on which the preceding determina-
tion of the comparative constitution of the post-stomal neural
arches of the cranium depends, are the zygopophyseal con-
nections of the human " petrosals." If the " petrosals" even
in one species can be proved to present the characters of
neurapophyses, the sclerotome to which they belong must
exist in addition to those to which the "ali-sphenoids" and
" orbit o-sphenoids" are referable. The existence of temporal
neurapophyses explains the existence of interparietal, in
addition to parietal bones in the mammal ; both of these
meta-neurapophyses taking part in the protection of the
developed cerebrum ; while the non-appearance of the anterior
or spheno-parietal in the bird, reptile, and fish, accords with
the complete development of the posterior or temporo-parietal,
repressed in the former by the influence of the cerebrum, and
by the full development of the ethmoido-frontal. I base my
determination of the separate existence and reciprocal develop-
ment of ethmoido-frontals and spheno-frontals, of spheno-
parietals and temporo-parietals, not only on my analysis of
the bones themselves in the series, but also on the evident
reciprocal influence which the superimposed cerebral mass in
the mammal, and the bulky organs of sense and uncovered
sense-ganglions of the lower Vertebrata have on the cranial
neural arches. I believe also, that in this, as in other
departments of inquiry, we are apt to look for greater sim-
plicity and uniformity in details than actually exist. The
simplicity of natural law consists in the comprehensiveness
of its general principles. In tracing these principles into
details, the complexity is found to be infinite.
The Hcemal Arches of the Post-stomal Cephalic Sclerotomes.
The clue by means of which we can alone be safely guided
to the morphological constitution of these arches, in the midst
of the varied complexity which they present to the compara-
tive anatomist, is afforded by embryology. The hsemal arches
186 ON THE MORPHOLOGICAL CONSTITUTION OF
of the post-stomal sclerotomes are developed each in the cor-
responding pair of " visceral laminse." By endeavouring to
ascertain, therefore, in which of these post-stomal " visceral
laminse'' the sclerous elements of the varied forms of the
post-stomal haemal arches are originally formed, the morpho-
logical constitution of the individual haemal arches may
reasonably be anticipated. If, again, I am correct in my deter-
mination of the constitution of the pre-stomal sclerotomes, the
allocation of the individual post-stomal haemal arches to their
proper centrums and neural arches follows as a matter of course.
From the observations more particularly of Eathke and
Eeichert, the formation of the osseous elements of the post-
stomal haemal arches in the " visceral laminae," is preceded in
each by a more or less distinct and continuous cartilaginous
streak or band. Eathke found seven pairs of these cartilagi-
nous streaks loosely connected to the basis of the embryo
head of the Blennius viviparus, and corresponding to the man-
dibular, hyoidean, first, second, third, and fourth branchial and
pharyngeal arches. In the adder the same indefatigable embryo-
logist and comparative anatomist found a cartilaginous style,
with a process directed forward in the position of the maxil-
lary, palate, and pterygoid bones, embedded in the first
visceral lamina, and its "superior maxillary process/' and
attached to the side of the basis of the primordial cranium in
front of its auditory region ; a similar style lay in the second
visceral lamina, and was firmly attached to the base of the
cartilaginous cranium behind, and external to the auditory
capsule ; a third style lay in the third visceral lamina, and
was also firmly attached like a rib to the occipital region of
the primordial cranium. Similar primordial haemal arches
have been found by Eeichert in the visceral laminae of the
mammal and bird, and by numerous observers in the Am-
phibia. It is important to observe again at this point, that
the relations of all these seven pairs of primordial haemal
THE SKELETON OF THE VERTEBRATE HEAD. 187
arches are similar. Firstly, all the visceral laminge in which
they are developed appear to consist of the serous, vascular,
and mucous layers united ; secondly, the cartilaginous streaks
are formed towards their inner surfaces, under the mucous
layer ; thirdly, the heart and vascular arches are on their ex-
terior, under the serous layer.
First Post-stomal Hcemal Arch. The constitution of this
arch must be determined by the examination of the develop-
ment of the first post-stomal visceral lamina. It has been
already stated that the process usually considered as the upper
part of the so-called " first visceral lamina " is, if its general re-
lations be taken into account, the posterior pre-stomal visceral
lamina in which the pre-sphenoidal haemal arch is developed.
The cartilaginous streak in the first post-stomal visceral
lamina of the mammal divides into two portions. The
superior and smaller of the two becomes the incus. The long
inferior portion is the cartilage of Meckel ; around the lower
part of which the corresponding half of the lower jaw is de-
veloped ; the upper part forms the slender process and the
head of the malleus. As the Eustachian tube, the tympanum,
and the external auditory passage, consist of the persistent
upper portion of the first visceral cleft, the cartilage of the
Eustachian tube, and the tympanic bone, which are continuous
with one another, and form the floor of these three spaces, are
developed in blastema deposited near the upper extremity of
the cleft. This blastema also forms the membrane of the
tympanum, into which the handle of the malleus shoots. It
is to be observed that this lower jaw and tympanic bone do
not originate in the primordial cartilaginous streak, but in
blastema deposited around it. The tympanic bone forms at
first an inverted arch across the visceral cleft, or a ring in-
complete above, which supports the membrane of the tym-
panum on the outer side of the attenuated portion of Meckel's
cartilage, which connects the malleus to the inner side of the
188 ON THE MORPHOLOGICAL CONSTITUTION OF
jaw. It then extends inwards, so as to form the floor of the
tympanum and Eustachian tube, folding up before and be-
hind, and thus, inclosing the incus and malleus, leaves the
latter connected to the jaw through the tympanic fissure.
The development of the first post-stomal visceral lamina
appears, therefore, to indicate at least four elements on each
side of the mandibular haemal arch in the mammal. The
tympanic element is probably complex ; the mandibular con-
sists of at least two portions, one on the outer, the other on the
inner side of the corresponding portion of Meckel's cartilage.
In the bird the omoid and palate bones are formed like
the pterygoid and palate bones of the mammal, in the so-
called " superior maxillary process." In the proper first post-
stomal visceral lamina, the primordial cartilaginous streak
divides, as in the mammal, into two portions. The upper
and smaller of the two becomes the quadrate bone ; the
lower and longer portion Meckel's cartilage becomes en-
veloped in the corresponding half of the lower jaw ; but
instead of the upper end of this portion forming the slender
process of a malleus, it remains as the peculiarly-formed
articular piece of the jaw itself. The original intimate con-
nection of the rudiment of the pterygoid bone, in the so-called
" superior maxillary process," with the upper or incudal por-
tion of the primordial cartilaginous streak of the first post-
stomal visceral lamina of the mammal, speedily diminishes ;
but in the bird, not only does the pterygoid or omoid bone
rapidly increase in relative size and configuration ; but the
quadrate portion of the first visceral streak does so likewise.
The latter also exhibits, attached to its outer side, as the
omoid is to its internal process, a styliform ossicle, the rudi-
ment of the quadrate-jugal bone, which again is connected
anteriorly to the jugal.
Eeichert, who has minutely described and figured the
development of this visceral lamina in the bird, makes no
THE SKELETON OF THE VERTEBRATE HEAD. 189
allusion to the remarkable indication which it affords of the
signification of the quadrate bone, and articular piece of the
lower jaw. It affords, as it appears to me, sufficient evidence
that the quadrate bone of the bird is the homologue of the
mammalian incus, and that the articular piece of its lower
jaw is the homologue of that ossified portion of the upper end
of MeckeFs cartilage, which in the mammal forms the slender
process of the malleus.
The quadrate bone has been hitherto considered as the
homologue of the tympanic bone in the mammal, not only
from the proximity of the latter to the condyle of the jaw,
but chiefly from its presumed absence in the skull of the bird.
But there appears to me to be sufficient evidence of its exist-
ence, not only in the fibro-cartilaginous frame which connects
the margin of the tympanic membrane to the mastoid, lateral
occipital, and basi-sphenoid, but more particularly in the thin
well-defined lamina of bone, which, apparently united to its
fellow of the opposite side, forms the floor of the tympanic
cellular space in the broad posterior portion of the basi-
sphenoid. As these apparently united laminae are continuous
with the single cartilaginous Eustachian tube, below the
single or double osseous Eustachian orifice, I am induced to
believe that they will turn out to be the feebly-developed
representatives of the tympanic bones of the mammal.
By a very beautiful analysis Professor Owen has proved
that the quadrate-jugal bone of the bird is the homologue of
the squamous portion of the mammalian temporal. I cannot,
however, give my assent to his determination of its special
homology, as a portion of the subdivided radiating appendage
of the maxillary arch. Its relations in birds and crocodiles,
in which it presents all its fundamental connections, appear
to me to show that it is an anterior actinapophysis of the
mandibular arch ; passing forwards to abut against the malar,
which I have already stated to be a posterior actinapophysis
190 ON THE MORPHOLOGICAL CONSTITUTION OF
of the ethmoidal haemal arch, or as in the lacertians against
the post-frontals. The squamous portion of the quadrate-
jugal bone is a mammalian superaddition, to adapt it to the
part it takes in the formation of the cranial wall. It is with-
drawn therefore from the quadrate or incudal portion of the
mandibular arch (which portion diminishes relatively), and
passes as the entire bone does in the lizards upwards to
be connected with the cranial wall. The development of the
first post-stomal visceral lamina in the bird appears therefore
to afford evidence that the mandibular haemal arch in the
bird and mammal includes a tympanic element, a quadrate
or incudal, a malleal or articular, and the elements of the
corresponding side of the lower jaw.
On the same grounds I am inclined to believe that the
articular piece of the lower jaw of the reptile and amphibian
is malleal like the corresponding piece in the bird, and not
the homologue of the condyle of the mammalian jaw. They
are all malleal portions of Meckel's cartilage retained in con-
nection with the jaw. In like manner, I am inclined to
believe that the so-called tympanic bone of the reptile and
amphibian, like the quadrate or so-called tympanic bone of the
bird, is not the homologue of the tympanic bone of the mam-
mal, but of the incus. The incus of the mammal has been set
free from its fundamental quadrat e-jugal and pterygoid con-
nections to co-operate with the similarly released malleus in
the economy of the ear. The absence of proper tympanic
bones in the reptile and amphibian is explained by the absence
or feeble development of the tympanic cavity. I am inclined
to think, however, that traces of them may be detected under
and between the basi-sphenoid and occipital of the crocodile, in
the walls of those canals which connect, as Professor Owen has
shown, by a common tubular communication, the Sella Turcica
and the tympanic cavities with the basis of the cranium.
The tympanic systems and lower jaw of the osseous fish
THE SKELETON OF THE VERTEBRATE HEAD. 191
form together a well-marked haemal arch, developed in the
first post-stomal visceral lamina of the embryo. From what
has already been stated regarding the sclerous elements which
result from the development of this visceral lamina in the
other Vertebrata, Professor Owen's view of the tympanic
system of the osseous fish, as the teleologically-divided homo-
logue of the quadrate bone of the bird, and tympanic bone of
the reptile, would appear to require additional evidence. We
are not yet in possession of materials for a rigorous determina-
tion ; but it appears extremely probable that the tympanic
bones of the osseous fish are morphological, as well as teleo-
logical elements. If the articular piece of the lower jaw be
assumed as the malleal portion of the persistent cartilage of
Meckel, the hypo-tympanic occupies the position of the in-
cudal element, connected, as usual, with the pterygoid. The
epi-tympanic is in the position of the proper tympanic element
of the mammal, while the pre-tympanic, in its relations to the
hypo-tympanic and pterygoid, closely resembles the quadrate-
jugal or squamosal.
The opercular bones form on each side of the mandibular
arch a series of actinapophyseal elements, which, from the
view already taken of such elements, would appear to be pos-
terior, as the quadrat e-jugal or squamosal is anterior in rela-
tion to the sclerotome. With regard to any traces of these
opercular or actinapophyseal elements in the mandibular
haemal arch of the higher Yertebrata, I must agree with Carus
in considering the cartilages of the external ear in the Mam-
malia as homologous with them. The objection of Eathke to
this determination of Carus that the cartilage of the concha
is attached to the tympanic bone so as to be situated at the
back of the auditory foramen that is, at the posterior margins
of the first visceral cleft appears to me to be met by taking
into account the peculiar curved form which the tympanic ele-
ment assumes in passing from before backwards across the cleft.
192 ON THE MORPHOLOGICAL CONSTITUTION OF
The allocation of the mandibular haemal arch to the post-
sphenoidal or first post-stomal sclerotome follows from the
analysis already made of the pre-stomal sclerotomes.
The Second and Third Post-stomal Hcemal ArcJies. As the
researches, more especially of Eathke and Eeichert, on the
development of the first visceral lamina, afford a clue to the
constitution of the corresponding haemal arch, so do the
labours of these observers in like manner indicate the nature
of the second and third arches. These arches are developed
in the second and third visceral laminae, and, from the varied
forms which they present in the series, could only have been
determined by an appeal to embryology.
In the mammal the primordial cartilaginous streak in the
second visceral lamina, and which is attached superiorly to
the auditory region, divides into segments, the uppermost of
which becomes the stapes ; while the succeeding become, in
succession with the intermediate soft portions, the " stapedius
muscle," the pyramid and its prolongation downwards, the
styloid process, the stylo-hyoid ligament, and the series of
sclerous elements which terminates below in the anterior
horn of the hyoid.
The primordial cartilaginous streak in the third visceral
lamina is attached to the occipital region, breaking up into
four segments ; the two upper disappear ; the two lower be-
come respectively the posterior horn and corresponding half
of the body of the hyoid.
In the second visceral lamina of the bird, in like manner,
the auditory columella is developed superiorly, and the feeble
anterior horn of the hyoid below, while the elements of the
suspensory or posterior horn of the hyoid are formed in the
third visceral lamina. The fibrous septum of the tongue and
the epiglottis of the mammal make their appearance in the
line of junction of the second and third visceral laminae. The
respective share taken by these two laminae in the formation
THE SKELETON OF THE VERTEBRATE HEAD. 193
of the so-called basi-glosso and uro-hyals in the bird remains
to be determined.
The precise observations of Eathke have shown that the
lateral halves of the feebly-developed hyoid of the ophidian
are formed by the lower portions of the primordial cartila-
ginous streaks of the second pair of visceral laminae, while the
auditory columellse are formed in their upper portions.
Eathke also found that the primordial cartilaginous streaks of
the third pair of visceral laminae, and which are attached to
the occipital region, disappear altogether.
There are no embryological observations in sufficient detail
to indicate the morphological relations of the more or less
complex hyoid apparatus in the chelonian and lacertian.
The so-called hyoid, or suspensory arch of the branchial
apparatus in the Amphibia, is developed in the second pair of
visceral laminae. The corresponding arch in the tadpole, and
the anterior or suspensory horn of the so-called " hyoid " of
the frog, are also developed in this pair of visceral laminae.
The suspensory arch of the branchial apparatus is attached to
the quadrate, or so-called " tympanic " piece of the mandi-
bular arch, and not to the base of the cranium. Eathke had
observed a filament extending between the auditory region of
the cranium and the quadrate cartilage of the tadpole. He
found that the so-called " malleus and incus " are developed
in this filament. According to Eeichert, this filament appears
to be the upper part of the second primordial cartilaginous
streak, which, in consequence of the peculiar manner in which
it curves forward superiorly towards the quadrate cartilage (a
curvature of the same kind towards the quadrate bone has been
observed by Eathke in the adder), becomes attached to it. In
consequence of this attachment, the hyoidean arch becomes
suspended to the quadrate portion of the mandibular ; and the
upper portion, between the quadrate cartilage and the auditory
region of the skull, becomes converted into those elements in
o
194 ON THE MOKPHOLOGICAL CONSTITUTION OF
the frog which have their homologues in the stapes of the
mammal, and the columella, with its cartilaginous extremities,
in the bird and reptile.
As the cartilaginous branchial arches of the tadpole, and
of the other Amphibia, are formed in the succeeding visceral
laminae, it would appear to follow, as a necessary consequence,
that the suspensory or hyoidean arch of the amphibian, with
its inferior mesial element, and along with the auditory
ossicles, is homologous with the anterior or suspensory part of
the hyoid, along with the stirrup-bones in the mammal, and
with the corresponding structures in the bird and serpent ;
and that the first branchial arch of the amphibian, with its
corresponding inferior mesial elements, are homologous with
the posterior horns and body of the hyoid in the mammal, and
with the posterior or suspensory horns, with the corresponding
inferior mesial elements of the hyoid in the bird. The so-
called posterior horns of the hyoid of the frog cannot, there-
fore, be the homologues, as Professor Owen's statements might
lead us to infer, of the posterior horns of the hyoid of the
mammal or bird. The posterior horns of the hyoid of the
frog are the remains of its posterior pair of branchial arches,
or enlargements of the posterior angles of its basi-hyals.
They are developed therefore in its posterior visceral laminae ;
while the posterior hyoidean horns of the mammal and bird
are developed in the third pair of visceral laminae.
As the skeleton of the hyoidean and branchial apparatus
of the fish is developed in the form of a series of inverted
arches in the corresponding visceral laminae, from the second
inclusive, we are obliged to conclude that its hyoidean arch is
the homologue of the stylo-hyoidean arch, with the stirrup-
bones or second post-stomal arch in the mammal ; and of
the corresponding portion of the hyoidean apparatus in the
bird, with the columellae ; and of the entire hyoid in the ser-
pent, with the columellae ; and that the first branchial arch in
THE SKELETON OF THE VERTEBRATE HEAD. 195
the fish is the homologue of the corresponding arch in the
amphibian ; of the posterior horns of the hyoid, and their
associated elements in the bird ; and of the posterior horns
and body of the hyoid in the mammal.
It has not yet been determined upon what developmental
change the suspension of the hyoidean arch of the fish to its
mandibular arch depends. It is probably of the same nature
as that which occurs in the tadpole, with this difference, that
the upper portion of the hyoidean arch disappears in the fish,
without developing a stapedial ossicle ; while its lower portion
remains permanently connected to the mandibular arch, in-
stead of regaining an attachment to the cranium.
The hyoidean and branchial arches of the fish are provided,
as has been already stated, with a well-developed double series
of actinapophyses, for the support of the branchiostegal
membrane and the branchial laminae. These actinapophyses
in the fish are foreshadowed in the tadpole by the tubercular
margins of its branchial styles.
The question may now be put if we are brought by
reference to the development of the parts to allocate to the
three post-stomal sclerotomes, haemal arches, consisting re-
spectively of the sclerous parts developed in the three anterior
post-stomal visceral laminae, to what sclerotomes are we to
refer the potential or actual haemal arches in the remaining
visceral laminae ? For reasons already stated, they cannot be
disposed of by referring them to a splanchno-skeleton, because
in that case the hyoidean arch or arches, and apparently the
mandibular arch also, must be referred to the same categoiy.
Neither can they be referred to any of the cervical, or trunk
sclerotomes ; because it would appear that the visceral walls
of the head are alone perforated by clefts. We are not yet
prepared to answer the question. It involves, as it appears to
me, the investigation of a residual quantity, the solution of
which will require some information in reference to certain
196 ON THE MORPHOLOGICAL CONSTITUTION OF
points, regarding which we cannot at present be said to possess
any. First, the development of the cyclostomes, but more
especially of branchiostoma ; secondly, the mode in which the
trunk sclerotomes increase in number and become arranged in
groups ; thirdly, the mode in which the same changes proceed
in the cranium ; fourthly, the determination of the series of
cephalic nervous centres, with their corresponding nerves
(neurotomes), more especially in the medulla oblongata, with
the causes which determine the grouping and order in which
the cerebral nerves pass through the walls of the cranium.
If there appear to be no sufficient developmental grounds
for making a distinction between the branchial arches of the
amphibian and fish, as belonging to a splanchno-skeleton, and
the hyoidean and mandibular as referable to the neuro- or
endo-skeleton, it becomes important to determine the signifi-
cation of the sclerous elements of the larynx, trachea, and
bronchial tubes. Without presuming to anticipate the minute
observation of the development of the parts themselves neces-
sary for the solution of a question of this kind, I would venture
to suggest that the proper cartilages of the larynx are de-
veloped from the inferior or mesial extremities of certain of
the visceral laminae ; and that the cartilages of the trachea
and bronchial tubes are a pair of highly-developed actinapo-
physeal systems, referable to one of the posterior visceral
arches.
Post-stomal NeuractinapopJiyses. In addition to the audi-
tory capsules, I recognise as post-stomal neuractinapophyses
more particularly those ossicles attached to the post-frontals,
raastoids, and external occipitals of fishes. Those attached to
the post-frontals may enter into the formation of the infra-
ocular bony arch. Those, again, which are developed on the
temporal and occipital sclerotomes are modified so as to
co-operate in the cranial suspension of the scapular girdle.
In conclusion, Goethe was the first to indicate the inter-
THE SKELETON OF THE VEKTEBRATE HEAD. 19*7
maxillaries, the maxillaries, and palatals, as elements of three
distinct cranial segments. In the course of my investigation
into the development of the teeth, I became early aware of the
correctness of Goethe's views on this subject, and have found
myself, therefore, unable to coincide with the doctrine of Pro-
fessor Owen as to the constitution of his palato-maxillary
or nasal hseinal arch.
198 ON THE MORPHOLOGICAL CONSTITUTION OF LIMBS.
VII ON THE MORPHOLOGICAL CONSTITUTION
OF LIMBS.
CARUS, maintaining generally the doctrine of cephalic
limbs, originally propounded by Oken, has at the same time
given much greater precision to the conception of the skeleton
of a limb, by viewing it as a system of elements radiating
from the exterior of a costiform arch. Professor Owen, while
he rejects, with British and the majority of foreign anatomists,
the fantastic doctrine of Oken and his immediate followers
with regard to cephalic limbs, has adopted the general doc-
trine of the skeleton of the limb as propounded by Carus, and
has developed and applied it with much ingenuity to the
illustration of actual structure. Professor Owen, has, however,
at the same time, by his allocation of the scapular girdle to
the occipital segment of the cranium as its hsemal arch, and
by the view which he takes of the opercular and branchio-
stegal elements, actually reproduced the doctrine of cephalic
limbs in another form. I do not propose in this communica-
tion to examine in detail the grounds on which Professor
Owen's general doctrine of limbs is based, but shall merely
state categorically those considerations which appear to me to
render it untenable.
1. It is highly improbable that the sclerous elements of a
limb should be derived from one, or at most two, sclerotomes ;
while its other elements, and more especially its nerves, are
supplied by a greater number of somatomes.
2. It appears to be highly improbable that the bones
which enter into the structure of an arm or leg, or that the
ON THE MOEPHOLOGICAL CONSTITUTION OF LIMBS. 199
corresponding sclerous parts in the lower animals, should be
the result of teleological subdivision of a single " diverging
appendage " or " archetypal element." Professor Owen
virtually admits that these "teleological" elements have a
morphological value when he institutes an inquiry into their
" special " and " serial homologies."
3. It appears to me that the scapular girdle cannot be the
haemal arch of the occipital segment of the head firstly,
because that segment is already provided with a haemal arch
in the series of transitory and persistent sclerous elements
developed in the third pair of visceral laminae ; secondly, be-
cause the scapular girdle is invariably found to be developed
at or in the immediate neighbourhood of that part of the
trunk of the animal where it is ultimately situated ; and,
thirdly, because it is improbable that the exceptions to a
general law should be more numerous than the instances in
which it is adhered to.*
The germs of the limbs make their appearance when the
ventral laminae of the primordial vertebral system are passing
down towards the haemal margin. At first they resemble
lappet-like projections of the inferior margins of these laminae ;
they extend along at least four or five of their segments, and
are situated in those regions of the body to which the future
limb is attached viz. in the pelvic and posterior region of
the neck, except in the fish, in which the pectoral lappets are
situated close behind the head. As the ventral laminae
extend downwards, the lappets retain a position more or less
elevated on the side of the trunk. At this stage they also
* It is somewhat remarkable that the only embryological evidence which
Professor Owen adduces in support of that portion of his Doctrine of Limbs,
in which the anterior limb is assumed to be developed at or close to the head,
is a reference to a passage in Rathke's Entwickelung der Schildkroten, in which
the author adduces the fundamental position of the bones of the shoulder viz.
the posterior region of the neck as a circumstance tending to explain their
ultimate passage into the thoracic cavity.
200 ON THE MORPHOLOGICAL CONSTITUTION OF LIMBS.
begin to exhibit a change in their form and position. They
become first sessile, then pedunculated, and the peduncle then
indicates by an angle at its centre the formation of the central
joint of the shaft of the future limb the elbow or knee-joint.
At the same time, what I term the plane of the limb is
changed. The lappet was originally developed in a plane,
which is coincident with the axis of the corda dorsalis.
This is the primary or fundamental plane of the limb ; and
when in this plane the lappet presents its radial or tibial
margin forwards towards the head, and its ulnar or fibular
margin backwards. When the limb leaves its primary posi-
tion, it lies in its secondary plane, which cuts the corda
dorsalis more or less obliquely, so that the radial or tibial
margins of the limb are directed more or less forwards and
inwards, and the ulnar and fibular backwards and outwards.
The permanently -sessile pectoral lappets or fins of the
osseous fish exhibit a peculiar modification of the same
movement ; they rotate on a transverse axis, so that their
anterior or radial margins are directed downwards and their
ulnar margins upwards. In the sharks and rays the pec-
toral and abdominal fins continue permanently in the primary
plane.
While the lappet is still in its primary plane, the rudi-
ments of the girdle of the future limb may be detected under
the integumentary covering, and therefore external to the
proper mass of the visceral wall of the body. In the pri-
mordial condition of the lappet of the wing of the chick,
Kemak has detected four parallel streaks running to its outer
margin, and continuous internally with the rudimentary
nervous structures of the four primordial vertebrae, with which
the attached margin of the lappet is connected.
Guided by embryological facts and conclusions, to the
more important of which I have just alluded, I have en-
deavoured to detect, more particularly in the osseous fishes,
ON THE MORPHOLOGICAL CONSTITUTION OF LIMBS. 201
plagiostomes, amphibians, and reptiles, the principle which
lies at the basis of the morphology of limbs. The view which
this inquiry has induced me to take of this subject I shall, in
conclusion, state very briefly.
1. A limb does not necessarily derive its elements from
one somatome about fifty segments of the trunk appear to
contribute towards the structure of the great pectoral fin in
the ray.
2. The nervous elements of the limbs appear, as in other
parts of the vertebrate animal, to indicate most distinctly the
morphological constitution of the sclerous elements. About
fifty spinal nerves contribute the greater part of their haemal
divisions to the pectoral fin of the ray ; and there are about
one hundred fin-rays a pair of fin-rays to each nerve, and
derived from each sclerotome. This correspondence does not
apparently exist between the fin-rays and nerves of the
osseous fish; but it may be fairly assumed that when we
have detected the developmental circumstances which induce
the attachment of the pectoral girdle of the osseous fish to its
cranium, as well as those peculiarities exhibited by its
anterior trunk sclerotomes, this discrepancy will be explained.
A more careful analysis than we yet possess of the number of
spinal nerves which supply branches to the limbs of the
higher Vertebrata is still a desideratum in this department of
the subject ; but it appears to be extremely probable, that in
the Mammalia at least five spinal nerves transmit filaments
to the five distal divisions of the limb. It would appear, too,
that, notwithstanding their plexiform arrangement at the
attached end of the limb, the greater number of the filaments
of each nerve reach their own morphological district at the
distal part of the limb. The radial and the ulnar nerves
are formed principally by the upper and lower roots of the
human brachial plexus that is, from the nerves of the
upper and lower primordial segments with which the embryo
202 ON THE MORPHOLOGICAL CONSTITUTION OF LIMBS.
limb was connected, and from which it derived its various
elements.
3. The nerves supplied to a limb are not the inferior or
haemal divisions of the spinal nerves, but radiating or actinal
branches of these divisions. The intercostal nerves are not
the nerves serially homologous with the roots of the brachial
plexus. The thoracic nerves, serially homologous with these
roots, are the intercosto-humeral and the succeeding middle
intercosto-cutaneous.
4. Each sclerotome supplying elements to the structure of
a limb supplies as a sclerous element a single actinapophysis ;
or, as in the rays, an anterior and a posterior that is, a pair
of actinapophyses.
5. From the structure of the mesial and lateral fin-rays of
the fish, the actinapophyseal elements of a limb may be
assumed as primordially segmented.
6. The fin-rays in the fish, and the phalangeal, metacarpal,
and metatarsal bones of the higher Vertebrata, are more or
less persistent conditions of the distal segments of the pri-
mordial actinapophyseal elements of a limb.
7. By atrophy, or otherwise, one or more of the segments
in the successive transverse rows of actinapophyseal elements
disappear, so as to leave in man, e.g., four elements in each
carpal row ; two in the fore-arm, one in the arm, two in
the next row for the coracoid and clavicle, one in the proxi-
mal row for the scapula.
8. The nature of the subsequent changes which the ele-
ments of the limb undergo, up as far as the shoulder or
hip, may be inferred from an examination of the paddle of
the Enaliosaur or Cetacean.
9. A careful application of the hypothesis to the limb-
girdles of the cartilaginous fishes, Amphibia, and reptiles,
leaves me strongly inclined to believe that the coracoid is an
actinapophyseal segment between the humerus and scapula,
ON THE MORPHOLOGICAL CONSTITUTION OF LIMBS. 203
prolonged downwards, towards the haemal margin of the body ;
that the scapula is a proximal segment, elongated towards the
neural margin of the body ; that the clavicle is the only other
retained segment in the same transverse row as the coracoid,
in front of it, and elongated like it in the haemal direction ;
and that the corresponding elements of the posterior limb
have a similar morphological signification.
DIVISION II.
ANATOMY, PHYSIOLOGY, PATHOLOGY.
DIVISION II.
VIII. ON THE EMPLOYMENT OF MATHEMATICAL
MODES OF INVESTIGATION IN THE DETER-
MINATION OF ORGANIC FORMS*
LECTURE I.
BIOLOGY, the science of which physiology and anatomy formed
parts, had been hitherto advanced by the study of the structure
of animals or vegetables* and the investigation of the functions
or uses of the various parts of that structure. This was the
object with which they sought to ascertain the uses and func-
tions of the particular parts of animals and vegetables under
examination, and to determine why the bones of any parti-
cular animal should be of a particular form. Biologists had
* The two Lectures on this subject formed the conclusion of Professor
Goodsir's course of lectures on Comparative Anatomy, delivered in the Uni-
versity in the Summer Session, 1849. The Abstract appeared in the Daily
Mail newspaper, July 31st and August 7th of that year. It had obviously
not been furnished or corrected by the author, and contained not only many
positive mistakes, but interpolations by the reporter. In the absence of any
manuscript copy from which to correct it, we had some doubts at first whether
it should be reprinted. But as it shows that the author's attention had been
directed many years ago to a department of inquiry, which, though compara-
tively neglected, undoubtedly affords room for useful research, and in which,
indeed, he was engaged up to within a few weeks of his death ; as it is an
attempt to illustrate that, the original form and law of growth of an organic
body being known, its form at any future time may be made a matter of
mathematical investigation, we have reproduced it, with the omission of such
phrases and errors as were most obviously due to blunders on the part of the
reporter. EDS.
206 MATHEMATICAL MODES OF
hitherto proceeded in this way ; knowing the habits of the
animals, and the form of the skeleton, and arrangement of the
muscles which co-operate with it in performing the movements
of the animals, they sought to determine what the particular
economy of the animal, under certain conditions, required. It
should be remembered that there was always a corresponding
harmony between the shape and connections of the organs of
the body and the motions peculiar to the animal. This in-
volves the principle of final causes, which entered so largely
into anatomical and physiological investigations. Upon this
principle we determined what were the functions, because there
was no other the parts were so well adapted to perform.
The wonderful progress of biology the science compre-
hending the study of anatomy and physiology or of compara-
tive anatomy, was attributable to this ; it owed its greatness
to this study of final causes that of the remarkable adapta-
tion of structures to particular functions.
The application of the doctrine of final causes was not,
however, the most fertile mode of procedure in physical inves-
tigations. It was only with respect to organised bodies that
it had enabled men of science to advance human knowledge.
It was very different in regard to chemistry, mechanics, etc.,
where no progress had been made till men of science had
thrown aside the consideration of final causes. But although
physical science did not advance till the introduction of the
inductive philosophy, and till final causes had been laid aside,
still the principle of final causes pervaded all nature. Take
in illustration the sun. But for the peculiar arrangement of the
sun in regard to the relations which he holds towards the earth
and other planetary bodies, his shape, and manner of moving
on his axis, we could have neither heat nor darkness, which
the economy of animals and vegetables rendered absolutely
necessary. Thus we might reason of the sun and earth, etc.,
from final causes, and might explain why the sun was so con-
INVESTIGATING ORGANIC FORMS. 207
stituted. But the natural philosopher, admitting all this,
arrived at his conclusion by another path altogether; and,
after he had reached it, ascertained that a final cause was at
work here also.
It was interesting to inquire why, in physical and che-
mical science, the progress had been so slow, by the appli-
cation of final causes, whereas anatomy had made great
progress by that means ? though after all, they were only at
the threshold. It was difficult to say why. It probably
had connection with the difference betwixt organised and
inorganised bodies. Every plant or animal formed a system
in which every part was related to some common centre, and
the whole . completely organised. In the study of any given
organised body, we had the whole of it before us. We
take into consideration its physical conditions, temperature,
medium, etc., yet each individual organism forms a system ;
we may refer all its parts, configuration, and phenomena, to a
principle residing in no other but individuals of the same
species. We are thus enabled to take the whole system into
consideration ; to enter upon its examination as a whole, and to
consider the relations of any part to any other given part ; we
thus see the reason why all its parts are adapted to each other.
It is different with regard to inorganised bodies, such as
the sun, whose parts, although constituted with reference to
the wellbeing of parts of our own system, have yet reference
to others. There is some common principle which governs
all these ; and this must be ascertained before we can reason
on the forms or uses of the parts of inorganic nature, and see
how all these parts are related. If it were possible to get
the whole system of the universe under the eye for examina-
tion with our telescopes and microscopes, we should then
have the inorganic world before us in the same position as
the animal or vegetable world, and should then see the
reason for its adaptations.
208 MATHEMATICAL MODES OF
Although biology had hitherto made great, decided, and
certain advances by the superficial method of inquiry, che-
mical and mechanical philosophy had gone far beyond it.
Motions, forms, and weights are now subjected to geometrical
analysis, and treated in the abstract, a result which had not
yet been attained in anatomical and physiological science,
but which in time would be so.
Without trenching upon the important considerations con-
nected with soul or spirit, or inquiring into the nature of the
spiritual organs, if any, of the animal or vegetable philoso-
phical questions, with which physiology and anatomy had
nothing to do, yet questions which should not be allowed to
lie uncultivated an acquaintance with the principles of phi-
losophy in their applications to the physiological sciences
ought to be gained. These constituted a set of sciences based
upon altogether different principles : 1st, on the internal
analysis of their own feelings, their own minds, and the prin-
ciples originally implanted within them, by consideration of
which, sound moral and intellectual conclusions were arrived
at ; and, 2d, an inquiry into the mental phenomena, or what-
ever they might choose to call them, presented by the lower
animals. This they might perform either by reasoning from
their own intellects downwards, just as they reasoned in
regard to their fellowmen, only passing down the scale ; or
they might compare the mental phenomena of the lower with
those of the higher animals thus building up a comparative
psychological science which would become simplified as they
passed down the series, and complex as they passed upwards.
The study by the anatomist and the physiologist, and by every
medical man, as far as the bent of his own mind admitted, of
these results of psychological science, was most important.
Anatomy had been hitherto advanced by the study of the
animal form and of the exact harmony under which only the
animal could exist. But there was another view that might
INVESTIGATING OKGANIC FORMS. 209
be taken. Was it not possible, by ascertaining the accurate
shape, the form and proportion between the parts, organs, and
whole body of any animal, to advance the study geometrically?
Suppose the anatomist gave the exact curvature of the surface,
the volume and proportions which different parts of the organs
might bear what their formal geometry was might become
matter of calculation. He might begin, by the lengths, and
breadths, and volumes of the different parts, by ascertaining
whether they have a correspondency, and exhibit a mathema-
tical relation, spherical or spheroidal curves, etc. These once
ascertained, he would become certain of the geometrical con-
struction, and could reason as to the probable forms of other
parts.
Impossible as it might appear, this had been effected in
Certain instances, and especially in a most beautiful manner
in regard to shells of molluscous animals, by the Eeverend
Professor Moseley, late of Cambridge,* who had made an exact
geometrical examination of shells, and especially of the Tur-
bines, which were possessed of a spiral curve wound round a
central axis, which curve had been found to be logarithmic, and
from it had been framed a series of formulae, by which the other
conditions of the shell could be predicted and found to exist.
By a very accurate measurement of the shell, mathemati-
cally, it was found that its spires increased in breadth in an
exact successive series, each one of which was a multiple, in
a certain ratio, of another. Thus there was a mathematical
principle arrived at, which could be carried out the shell
must possess this form, and could possess no other. It had
a spiral curve, and the properties of that curve pointed it
out to be a logarithmic curve, one which would reproduce
itself; a curve formed by a thread wound off the exterior,
would trace the form of its operculum ; and the mouth of
the animal was remarkable for geometrical symmetry. As
* Philosophical Transactions, 1838, p. 351.
P
210 MATHEMATICAL MODES OF
the shell was formed by the soft parts of the animal
those parts, though not possessed of the rigidity of the
outer shell, yet, if we measured their textures, their relative
proportions and rates of increase, we should also find that
they were formed according to a mathematical law. It was im-
possible, therefore, they should not form a general harmony !
How rapidly science advances ! A few years ago it was sup-
posed that the capillary vessels would model anything, and
that parts were formed by the extremities of these. But if we
admitted absorption, and the death of precise parts, we might
expect to ascertain the mathematical law of the body. The
period was not far distant when this subject would embrace a
much greater number of mathematical rules. No subject could
better employ those possessed of mathematical talents than
the application of modern analysis to organised bodies. They
must begin with the Mollusca. Professor Moseley had exa-
mined only the turbinated and discoid shells. The logarithmic
curves varied in different shells. But it would come to this
at last, that instead of the naturalist describing these bodies
by a long roundabout enumeration of their colours, sizes, etc.,
he would just give the mathematical curves which indicated
them. This was already done in crystallography, where crystals
were classified according to certain geometrical relations.
By Professor Moseley's investigations matter had been
added to the stock, and something had been done towards
the investigation in this manner of animals and vegetables.
Professor Moseley, by mathematics, had ascertained that a
process must go on, which other naturalists had not discovered
namely, by the revolution which the operculum of the
shell must make. It was. easily conceived that the oper-
culum made a revolution round its axis. The mouth was ol
a particular figure. Cut any part in a certain direction (the
direction of the plane of its axis), and every section would
give a form exactly similar to the form of the mouth. The
INVESTIGATING ORGANIC FORMS. 211
form of a turbinated shell was produced by the revolution of
the perimeter of the figure round the axis of the shell. In
the Nautilus the figure was that of an ellipse, which revolves
round its minor axis, and increases in geometrical progression
without ever changing its form as it revolves. A turbinated
shell revolving round its axis shows the figure carried forwards
along the axis of revolution, from the apex of the spire to its
termination. They might do this by cutting a piece of paper
to the figure of the turbinated shell. It would be found that the
figure was always the same, but increased. Professor Moseley
ascertained this in two ways 1st, after the curve had been
ascertained ; and 2dly, by a very curious investigation of the
operculum. He had ascertained that the spiral possessed the
peculiar properties of a logarithmic spiral; hence the oper-
culum was found to form a very convenient measure of the
shell itself and all its parts. The operculum being fixed, as
the shell increased in size it underwent a gradual increase
the size of the mouth gradually increased with the size of the
operculum. Now, if the operculum were merely pushed
forward by the animal, one of two circumstances would occur
it would either require new calcareous shelly matter (but it
was not so), or there would be, as indeed was the case, a much
more precise method of extension by the deposition of addi-
tional matter along the lower margin of the shell which formed
the tangent of the curve.
There were other examples of a similar kind. Take one
of the Goniums, a little animal or vegetable structure existing
amongst the polygastria, and consisting of four cellules in
a square plate, as also the Sarcina Yentriculi. The Goniums
and others were rectangular forms. They were all squares.
And why ? They reproduced themselves in a geometrical pro-
gression, and that because each individual consisted of four
cells, and four only, until it was reproduced by other four.
The law of its reproduction was by a geometrical series
212 MATHEMATICAL MODES OF
multiples of four, in extreme rapidity. Four cells would
always represent a flat figure, and recur in the form of a plate ;
all the angles might not in every case be alike, but it would
always be in laminse. The reproduction of the confervse was
also by the multiplication of cellules. Certain silicious poly-
gastric animals the Diatomacese, and some others existed in
two halves, reproducing each into two. These would always
form a line, or linear series, increasing in length, and not in
breadth. The line might form a curve, but this linear form
was a necessary consequence of the mode of reproduction.
This was a sketch of what might be done ; and it ought
to be done by a mathematical investigation of the animal
body, its masses and organs, or what was of more importance,
its ultimate atoms. This was a difficult process, but we
should not despair of arriving at it. Suppose the science
were so far advanced that we could obtain the formal mathe-
matical expression of forms, the same as astronomers did
before the time of Newton, when they ascertained the motions
of the planets in their orbits, and the curves that bounded
these bodies. Newton, from the geometric forms, made out
THE LAW OF THE FORCE.
We have merely to ascertain the law of the force. This
can never be done till we have got the mathematical forms.
We are probably far from this. But meanwhile science makes
great progress on the principle explained at the beginning of
this lecture. There is room to get into another inquiry
naturalists have never dreamed of, probably from not having
had a mathematical education. Those of them who had such,
and a taste for biological studies, would do well to carry out
the mathematical study. What the chemical and other forces
had to do in the animal economy could only be made out after
the forms of matter were found out. It by no means trenched
on the other department the mental and spiritual although
the two went together.
INVESTIGATING OEGANIC FORMS. 213
LECTURE 2.
Professor Moseley's paper contains the germ of what would
yet form a new epoch in natural science, though known only
to a few mathematicians, who probably considered it merely as
a curious and ingenious memoir.
As a very remarkable coincidence, Newton had shown in
his Principia that if attraction had generally varied as the in-
verse cube instead of as the inverse square of the distance, the
heavenly bodies would revolve, not in ellipses but in logarith-
mic spirals, rapidly diffuse themselves, and rush off into space.
It would be curious that if the law of the square were the law
of attraction, the law of the cube might therefore prove to be
the law of production. He did not say that this was the case.
But if this law of force were admitted, and cellules grew by a
certain law, we could thereby explain how all cellules passed
off from one another, and how all form was produced namely,
in a rapidly-increasing geometrical ratio, instead of revolving
round an axis. Probably the logarithmic spiral would be
found to be the law at work in the increase of organic bodies.
Another remarkable confirmation of the possibility of
carrying out the principle of geometrical investigation where
we would least expect to find it ; in reference to the forms of *
the most highly-organised bodies with which we are acquainted,
but which had yet been found to be bounded by geometric
figures, has recently been pointed out.
For the examination of the geometric outline of the human
body we are indebted to Mr. D. K. Hay.*
By the geometrical construction of a diagram, we should
now be enabled to trace the outline of the skeleton ; and all
the leading parts of the body would come out exactly as they
ought to be.
* On the Human Figure, 4to, 1849 ; Natural Principles of Beauty, 1852 ;
The Science of Beauty, 1856.
214 MATHEMATICAL MODES OF
In order not to involve what was undeniable in Mr. Hay's
theory in any hypothesis and those who had studied Mr.
Hay's works would know that much in them was based on
harmonical theories these last should be kept out of view.
What might be shown was, that the artist accustomed to draw
the outline of the figure could do so, and would thereby find
his figure better proportioned, nor would he be liable to com-
mit those glaring blunders, which, however good figures might
be artistically, were offensive to the critical anatomical eye.
The first diagram in Mr. Hay's book* was that of a female
figure seen in front with the arms by the side. Mr. Hay first
drew a line which represents the full height of the figure.
From the upper extremity of this line he drew lines making
with it respectively angles equal to l-3d, l-4th, l-5th, and
l-6th of a right angle ; and from the lower extremity a line
making l-8th of a right angle. The point in which the two
last lines, making respectively l-6th and l-8th of a right
angle, intersect one another determines the semi-breadth of
the figure. Passing through the upper extremity of the ver-
tical line, a circle and three ellipses were described the line
which joins the extremities of the axes major and minor of
the first ellipse being the first of the lines above drawn, and
that which joins the extremities of the axes of the second
being the third of the said lines. These give the skull,
face, and neck. A third ellipse, similar to the first of these,
but larger, represents the body. The other lines are few and
simple in their relations, the characteristic being that they make
an angle of l-3d and l-5th of a right angle with the vertical
line. It will be seen that the ruling feature in Mr. Hay's
theory is that 'position is determined ly direction, not ly distance.
The diagrams show how, in the very simplest way, by
integral divisions of a right angle, a succession of lines had
been attained which corresponded precisely to the position of
* Natural Principles of Beauty, Plate I. Figs. 1 and 2.
INVESTIGATING ORGANIC FORMS. 215
the symphysis of the lower jaw the lower part of the
chin ; the upper part of the dorsal vertebrae ; the tip of
the shoulder upper end of the humerus (showing also the
breadth) ; the upper part of the sternum and average posi-
tion of the upper parietes ; the middle of the dorsal region
sixth and seventh dorsal vertebrae ; the nipple in the female ;
the upper part of the lumbar, and lower part of the dorsal
region ; the exact position of the elbow-joint ; the upper part
of the pelvis the haunch-bones ; the lower edge of the last
lumbar vertebrae ; the upper part of the sacrum ; the line so
long familiar to artists as dividing the body and correspond-
ing with the upper part of the pelvis ; the tip of the longest
finger a remarkable feature in drawing the body ; and the
upper end of the tibia, one-fourth of the body.
Undoubtedly, in all organic bodies, as they had seen in a few
examples, certain geometrical principles would be discovered,
and though Mr. Hay's diagram was artificial and empirical,
because it had been used empirically in the meantime, yet it
gave correctly all the parts.
Mr. Hay had at first proceeded by following theoretical
views. He believed the human body to be beautiful, and to
give pleasure artistically because it included certain symme-
trical and geometrical forms.
His investigations were limited at first to the human head,
the anterior part of which he had found to be spheroidal, and
the posterior, seen from the side, from above, and from below,
to be included in a sphere and oblate spheroid, formed by the
revolution of a circle and an ellipse. These figures enclosed
certain triangles. The triangle of the circle was a right-angled
isosceles triangle ; the triangle of the ellipse a right-angled
scalene. They varied, according to their peculiar character,
within certain limits.
With these views he had been able, by continuing the
system of geometrical construction, which he had found sue-
216 MATHEMATICAL MODES OF
cessful in the geometrical analysis of the head, downwards
through the thorax and body, and by a series of measurements
of individuals, to construct triangles and figures in combina-
tion, enclosing within them the great outlines of the body.
In the first place, dividing the figure into five parts, on
each of which an equilateral triangle was produced or formed,
doubling the right-angled scalene triangle, whose angles
were 30, 60, and 90, he got the breadth of the shoulders
and various points of the figure. A remarkable confirmation
of Mr. Hay's views was arrived at by the division of the body
into five, which might be effected by continuing downwards
the equilateral triangle contained within the second oval of
the head in a succession of figures. By this succession they
had also the breadth of the figure.
The angles of the first right-angled equilateral triangle
were 45, 45, and 90 ; those of the second, or scalene, being
half of the equilateral triangle, 30, 60, and 90 ; and those of
the third, or right-angled triangle, being the primary angle of
the pentagon, as seen at the neck, 18, 72, and 90. The
ratio of the angles in the right-angled equilateral triangle was
as 1 to 2, in the scalene as 1 to 3, and in the third right-
angled triangle as 1 to 5. The angles of the other triangles
were 22 30', 67 30', and 90 ; and 11 15', 78 45', and 90,
and their ratios 1 to 4, and 1 to 8 ; whilst the angles of the re-
maining triangle were 15, 75, and 90 the angle at the
apex bearing a ratio to the right angle of 1 to 6.
They would thus find that, in regard to the various angles,
Mr. Hay had arrived at them partly on theoretical views.
He was just as much entitled to theorise as any other man of
science. No discovery had ever been made without hypothesis.
He had started, expecting to find in the proportions of the
human frame a musical harmony ; and, by continual measur-
ing, had at last been able to construct a figure, partly hypo-
thetically, but which was found to correspond with nature.
INVESTIGATING ORGANIC FORMS. 21?
Having arrived at these conclusions in a legitimate manner,
he found the tonic repeated thrice, the dominant twice, and
the mediate once. The ratios, which they would perceive the
angles of the triangles bore, as laid down, were ratios which
held in the musical chord. By simply prolonging the trans-
verse lines of the diagram, a perpendicular line would be
intersected in a series of fractional parts, all of which were
indicated in the musical scale. If this perpendicular were a
musical string set a-vibrating, it would vibrate, for instance,
first as a whole string, then as two halves or octaves, then as
third parts or fifths ; another set of vibrations repeated the
octaves viz. fourth parts or double octaves ; another series
of vibrations divided the chord into fifth parts or thirds, etc.
This was certainly very remarkable. The artist who drew
as Mr. Hay directed would produce a figure infinitely more
correct than by the mere eye or a prolonged study of figures.
It was remarkable that the angles which he had attained by
correcting himself, by careful measurement, and by preserving
a certain ratio of one to another, should repeat themselves at
intervals representing musical intervals.
In the female figure the common or primary chord of
music, where 2, 3, and 5 were the leading numbers, was indi-
cated. The male form differed essentially and materially
from the female. Mr. Hay had begun his researches with the
female form. It was necessary for him also to construct a
diagram of the male ; and he had made trials, but not at
random, from which he thought it probable that the male
differed from the female in harmonic ratio. By making the
figure on a dominant triangle, for which, instead of 30,
he took 33 45' (and this related to the dominant angle
in the female, in the mathematical ratio of 9 to 8, or, to
express it musically, as a major tone to a minor tone), he was
enabled to construct a diagram for the male into which you
can't draw a female figure ! It comes out a male ! It would
218 MATHEMATICAL MODES OF
be remembered that the breadth of the pelvis was less, and the
outlines of the thigh-bones were situated closer together, in the
male than in the female ; that also in the female the knees were
brought together. Besides these distinctive marks, Mr. Hay
had, moreover, of himself, brought in the female elbow and
bent out the wrist ; although he was not aware, till he (Pro-
fessor Goodsir) had told him, of the difference in this respect
between the sexes for in a well-made man the arm was
always perfectly straight. This showed that, however artifi-
cial the system, the artist might depend upon it for giving to
the figure the correct anatomy in its great leading features.
The breadth of the thorax from side to side had been ascer-
tained by the general angle, which gave the breadth of the
male thorax (33 45'), and so increased in like proportion.
In regard to the depth, by assuming the angle 30 again, and
taking the average depth of both male and female ; on the
harmonic hypothesis the angle for production of the equi-
lateral triangle, half of which gave the depth of it in the
female, would be 27. Now 33 45' to 30 is as 9 to 8 ;
whereas in the female, 30 is to 2*7 as 10 to 9 these being
the ratios of the major and minor tones in the science of
musical harmony.
This very ingenious, piece of research was an approach to
those principles indicated in the previous day's and this day's
lectures. With regard to Mr. Hay's views, if they followed
the directions in the diagram, they would be mechanically
correct in filling up, which a little practice would enable them
to do, for the male as well as for the female, the outline of a
figure anatomically correct.
This was an extremely useful result. If they were to view
it in no other light, artists were greatly indebted to Mr. Hay.
This could not be denied. And, without involving himself
or them in the hypothesis on which it depended in the ratio
of angles, or the number of times which they were repeated
INVESTIGATING ORGANIC FORMS. 219
they were not to despise that hypothesis, because it was
by working it out Mr. Hay had been enabled to frame this
diagram. They could not deny that harmonic proportion
was something, if they admitted the diagram to afford a
correct anatomical outline ; for it must exist in nature.
This was something like an approach to a general geomet-
rical inclusion of the surface of the body by the revolution
of triangles, and the perimeters of certain figures, including
certain masses of the body. If they included the general
mass, there was reason to expect that the outline of the sub-
ordinate parts would be arrived at by a process of the same
kind. They were all produced by some law, according to
which the parts of the body were formed. If this law were
complete, they should have a formal anatomy of the body
a geometrical outline, however complicated a complex geo-
metry but they must believe in it. There were no parts
of the body not injured not even parts diseased that were
not geometrical structures, however complex. It was only
after knowing these they could arrive at the law of the force.
He had not, in this hurried manner, been able to do that
justice he was anxious to see done to Mr. Hay's not merely
ingenious diagram ; but by the lecture of yesterday and to-day,
although not yet in the exact scientific position reached with
regard to the shell by Professor Moseley, yet he was desirous
to show that the harmony and geometrical analysis of the
human body, by continuing the research, would rapidly ad-
vance that department of biological knowledge.
220 ANATOMY OF THE KNEE-JOINT.
IX. ON THE HORIZONTAL CUKVATUKE OF THE
INTERNAL FEMORAL CONDYLE ; ON THE MOVE-
MENTS AND RELATIONS OF THE PATELLA,
SEMILUNAR CARTILAGES, AND SYNOVIAL
PADS OF THE HUMAN KNEE-JOINT.
ASSUMING the ordinary descriptions of the human knee-joint,
and the more precise observations of the brothers Weber
(Mechanik der Menschlichen Gehwerkzeuge, 1836), as present-
ing the present state of information on the subject, I shall
proceed to explain the arrangement and use of the peculiar
curvature at the fore-part of the inner condyle of the femur,
as recently determined by Professor Meyer of Zurich (Die
Mechanik des Kniegelenks, Mullet? s Archiv., 1853) ; and the
movements and relations of the patella, semilunar cartilages,
and synovial pads of the articulation, as observed by myself.
Before entering on the peculiarities of the inner condyle,
I may remind you that the knee-joint consists of two articu-
lations, with a common synovial membrane, the patello-
femoral, and the femoro-tibial, the latter being double. The
articular surface of the femur is consequently divided into
a trochlea for the former, and two condyles for the latter;
the condyles being separated from one another by the inter-
condyloid fossa, and from the trochlea by two shallow oblique
grooves.
Anatomists had not hitherto noticed that the so-called
obliquity of the inner condyle of the femur is in fact, as
Meyer has pointed out, a curvature of its anterior third, with
ANATOMY OF THE KNEE-JOINT. 221
its concavity directed backwards, outwards, and downwards.
The two posterior thirds of the inner condyle pass backwards
parallel to, and have the same general form and extent as, the
entire outer condyle of the bone. The curved portion or
anterior third of the usually so-called inner condyle may
therefore be conceived as a part intercalated between the
patellar trochlea and the proper inner condyle.
According to Meyer, the mechanical advantages which
result from the peculiar antero-posterior curvatures of the
femoral condyles, which the brothers Weber concluded, from
their admeasurements, to be spirals, may be with greater
simplicity assumed to consist, as his own admeasurements
suggest, each of two circular segments, the posterior of 120,
the anterior of 40, the radius of the former being to that of
the latter as 5 to 9. The horizontal curvature at the fore-part
of the inner condyle, or, more precisely, the oblique curvature,
may, as Meyer states, be conceived as a segment of 60 of the
margin of the base of a cone, the axis of which is directed at
an angle of 45 downwards, outwards, and backwards, in front
of the spine of the tibia, so that its apex is situated in the
external condyle of that bone.
In flexion and extension, therefore, of the knee-joint, as
long as these movements are confined to the outer condyle,
and the two posterior thirds of the inner condyle of the femur
with the condyles of the tibia, they take place round two
transverse axes, which pass respectively through the centres
of the posterior antero-posterior circular curvatures of the
femoral condyles, and the centres of the anterior. To simplify
the conception, however, of this part of the arrangement,
Meyer assumes as sufficiently accurate a single transverse
axis.
In the first third of flexion, and in the latter third of ex-
tension, the movements of the femur and tibia take place
round the oblique curvature or anterior third of the internal
222 ANATOMY OF THE KNEE-JOINT.
femoral condyle ; and involve, in addition to the completion
and commencement of flexion and extension respectively, a
movement of rotation of the tibia and consequently of the
leg and foot inwards in the former, and outwards in the latter.
These remarkable movements of rotation inwards and out-
wards, inseparable from the commencement of flexion and the
completion of extension, take place round the axis of the
ideal cone already alluded to. This axis Meyer denominates
the oblique axis of the knee-joint.
These movements of rotation, combined with flexion and
extension, must be carefully distinguished from those of which
the joint is capable when considerably flexed. The latter,
with which anatomists are already familiar, take place, in
general terms, round a prolongation of the axis of the tibia.
This axis Meyer denominates the rotation-axis of the knee-
joint.
The most remarkable ligament concerned in the move-
ments round the oblique axis of the joint is the external cru-
cial, which becomes tightened in extension, as the movement
round the oblique curvature of the inner condyle proceeds,
and thus acts, from its obliquity, in a direction from below, up-
wards, backwards, and outwards, so as to guide the rotation
of the tibia outwards.
The discovery of the oblique axis of the knee-joint has
enabled . Meyer to determine with greater precision the action
of certain muscles of the thigh. The use of the peculiar mode
of insertion, hitherto unexplained, of the sartorius, gracilis,
and semitendinosus, becomes- evident. Their tendons, passing
down behind the inner side of the knee, curve forwards and
outwards on the tibia ; so that these muscles effect that
rotation inwards which is a necessary accompaniment of the
commencement of flexion. These muscles produce this
rotation directly that is, by an adaptation of their tendons
to the purpose ; but, according to Meyer, the proper flexors
ANATOMY OF THE KNEE-JOINT. 223
of the knee, the biceps and semimembranosus, only act in-
directly as rotators, through the medium of the articular
surfaces and ligaments. I conceive, however, that the
latter may act directly in producing rotation inwards at the
commencement of flexion ; for its tendon, instead of being
inserted, as is usually stated, into the back part of the inner
tibial condyle, passes forwards and outwards round the head
of the bone in a distinct groove, in which it moves, being kept
in its place by prolongations of the internal lateral ligaments
of the joint, and thus presenting the same general mode of
insertion as the three muscles already alluded to.
The rotation outwards, at the completion of extension, is
produced indirectly by the quadriceps-extensor ; the form of
the articular surfaces, and the tightening of the external
crucial ligament, co-operating with the group of extensor
muscles.
Meyer has detected a very beautiful adaptation of parts in
connection with this latter movement, and has thus explained
the characteristic enlargement, and the extensive attachment
to the patella, of the vastus internus muscle. When the knee
is extended, the ligamentum patellse, instead of being perpen-
dicular, will be found to pass downwards and outwards to its
tibial attachment, which has moved outwards in the rotation
of the leg. The lower portion of the vastus internus is en-
larged, and the upper portion of its tendon is attached to the
greater part of the inner edge of the patella, for the purpose
of preventing that bone from being pressed against the outer
part of the femoral trochlea during the rotation outwards of
the leg, by drawing it inwards and upwards, and keeping its
axis in the line of the ligamentum patellae ; while the lower
portion of its tendon passes down to be attached somewhat
obliquely to the inner side of the head of the tibia, and thus
assists directly in rotating the leg outwards.
Meyer has also shown that, in standing quietly upright
224 ANATOMY OF THE KNEE-JOINT.
on one or both limbs, the knees are not necessarily kept
straight by continued action of the extensor muscles, for the
ligaments of the patella may be slack. The continued
extension cannot be the effect of the superincumbent pressure
of the body, for the transverse plane, in which the common
centre of gravity is situated, lies behind the transverse axes
of the knee-joints. Two arrangements conduce to this re-
markable example of economy in muscular action. When the
foot is on the ground, and the knee extended, the inward
rotation of the leg in the commencement of .flexion cannot
take place ; and if the pelvis and trunk are kept erect, the
reverse rotation of the thigh-bone outwards is prevented by
the tightened condition of the ileo-femoral band of the hip-
joint : but if the trunk and pelvis be inclined forwards,
although the ileo-femoral band is relaxed, and the femur
relieved, the tendency to flexion of the knee-joint is removed
by the passage of the line of gravity to the front of the
transverse axis of the articulation. The thick longitudinal
band of the fascia lata on the outer side of the thigh, ex-
tending from the anterior superior spinous process of the
ileum, and from the inferior attachment of the tensor vagina
femoris to the fore part of the outer condyle of the tibia
(ligamentum ileotibiale), is another arrangement for econo-
mising muscular exertion ; for as long as the pelvis is kept
erect on the heads of the thigh-bones by the glutei maximi
muscles, it is evident that these ileo-tibial bands must tend to
keep the knees extended, and transfer the action of the
quadriceps-extensor to the great muscle of the hip.
The patella exhibits various interesting relations during
the movements of the joint ; and in addition to those observed
by Meyer, others hitherto unrecorded may be pointed out.
Meyer states that the under half of the patella is in contact
with the femoral trochlea in extension, and the upper half in
flexion ; but if the bone is carefully examined, the following
ANATOMY OF THE KNEE-JOINT. 225
configuration and relation of its articular surface will be
detected. Instead of two faces, a greater external, and a
lesser internal, separated by a perpendicular ridge, as usually
described, the surface presents, in every instance, six, frequently
seven, facets, separated from one another by two perpendicular
and two transverse ridges. The external perpendicular ridge
is the one commonly described. The internal cuts off a small
elongated perpendicular facet at the inner edge of the surface.
The two transverse ridges only extend inwards to the inner
perpendicular ridge, so as to separate from above, downwards,
two superior, two middle, and one or two inferior facets, the
external of the two latter being constant. The relations of the
articular surface of the patella present four groups. In
complete flexion, the internal or perpendicular facet is in
contact with a remarkable crescentic facet, which bounds the
oblique curvature of the inner condyle of the femur. In none
of the other positions of the joint is this internal patellar facet
in contact with an opposite cartilaginous surface, but is
covered or sheathed by what may be denominated the internal
patellar pad. At the same time, the external superior facet
lies upon the fore part of the external condyle of the femur
below and behind its bounding groove. These two facets are
the only parts of the patella which come in contact with the
proper femoral condyles. They do so only in complete flexion ;
and in this state all the remaining facets are in contact with
the great infra-patellar pad, and the so-called mucous liga-
ment.
In the second stage of extension, the superior internal and
external facets are in contact with the inferior portions,
respectively of the inner and outer halves of the femoral
trochlea ; the internal perpendicular facet being sheathed as
before stated ; and the remaining facets being in contact with
the great infra-patellar pad.
In the third stage of extension, the superior internal and
Q
226 ANATOMY OF THE KNEE-JOINT.
external facets leave the femoral trochlea and become sheathed,
and the space occupied partly by the supra-patellar, but
principally by the supra-trochlear pads. The middle internal
and external patellar facets now come in contact with the
middle portions respectively of the inner and outer halves of
the femoral trochlea ; while the internal perpendicular and
the two inferior facets are sheathed and padded as before.
In the fourth or last stage of extension, the middle internal
and external facets also recede from the surface of the trochlea,
and along with the internal longitudinal already sheathed,
become applied against the fore part of the femur above its
articular surface, the intervening space being stuffed by the
oiipra-patellar, supra-trochlear, and upper pads, in the ascending-
cul-de-sac of the synovial membrane. In this last stage,
the only portions of the patella in contact with the cartilaginous
surface of the femur, are the inferior internal and external
facets, or the latter, if one only exists. These slip somewhat
abruptly upwards and inwards upon a narrow ledge or furrow,
which terminates the femoral trochlea above, and forms a
resting-place for the inferior facets of the patella in the
complete extension of the joint.
Attention should be directed to the fact, that the patella,
in complete flexion, lies so much to the outer side of the
joint as to leave the inner condyle, with the exception of
the crescentic facet, exposed in front. Meyer has pointed
out that the external position assumed by the patella in
complete flexion depends on the external patellar retina-
culum, which consists of two oblique bands, extending from
the outer edge of the bone to the anterior margin of the
ileo-tibial band of the fascia lata already alluded to ; and
which, as it slips backward during flexion, drags the patella
by means of the external retinaculum outwards.
In complete extension, again, the patella lies at the inner
side of the upper end of the joint, with its long axis directed
ANATOMY OF THE KNEE-JOINT. 227
outwards and downwards. It assumes this position under
the action of the lower portion of the vastus internus, which
may now be considered as an adductor patellae. It will be
observed also, that the passage forwards of the lower end of
the ileo-tibial band, and the consequent slackening of the
external retinaculum, permits the bone to take up this internal
position. In consequence, therefore, of the movements of the
patella, in harmony with the oblique rotations of the knee-
joint, the bone, under the influence of its external retinaculum,
and of the lower part of the vastus internus, describes a curved
path, the concavity of which is directed upwards and outwards.
It is also guided in this path by the form and direction of the
femoral trochlea, and particularly by its upper and outer
portion, which, as is well known, projects considerably
upwards, forwards, and inwards, so as to convey the patella
to the inner side.
The spaces, which would otherwise be produced by the
recession of certain parts of the cartilaginous surfaces from
one another in the movements of some joints, are occu-
pied by movable and yielding structures of two kinds
interarticular fibre-cartilages, and the so-called Haversian
glands, which may be denominated synovial pads. The for-
mer occur when resistance to pressure is to be provided, the
latter when space is only to be occupied. The semilunar
fibro-cartilages of the knee belong to the former category ;
and the brothers Weber have pointed out generally how
these elastic crescentic masses move backwards and for-
wards in the flexion and extension of the joint. But Meyer
has indicated with greater precision their peculiar functions.
The external semilunar cartilage must be viewed as an ap-
pendage to the external condyle of the femur, with which it
moves backwards in flexion, forwards in extension. These
movements are facilitated by its circular form, the approxi-
mation of its horns, its non-attachment to the anterior external
228 ANATOMY OF THE KNEE-JOINT.
lateral ligament, although the posterior external lateral
ligament gives off a peculiar arrangement to support its
posterior limb. The internal semilunar fibro-cartilage, again,
must be regarded as an appendage to the internal condyle of
the tibia, to which it is fixed by the two internal lateral
ligaments. It resembles a curved, yielding, but elastic railway
on the upper surface of the inner condyle of the tibia, along
which the corresponding condyle of the femur rolls backwards
and forwards.
The term of synovial pad may be applied to the mass of
vascular fat covered by the synovial membrane, and usually
called a Haversian gland, or synovial vascular fringe. Some
years ago, I directed attention to the structure and rela-
tions of these bodies, as corroborating the opinion of Havers
regarding their function (Anat. and Pathological Observations,
p. 42*), and have now ascertained that, in addition to their
probable function in supplying synovia, they act undoubtedly
as movable stuffing-pads, which not only smear the synovia
over the opposite cartilaginous surfaces, but steady the move-
ments of the joints by passing into the spaces left between
the surfaces during action. These pads are so constant in
their form and relations as to indicate the general character
of the movements the joint is capable of.
The principal structure of this kind in the knee-joint is
the great infra-patellar pad the mass in connection with the
so-called alar and mucous ligaments. It presents a posterior
free surface of a quadrilateral form, which is applied against
the cartilaginous surface of the femur, principally in the
extended condition of the joint ; a superior free margin cut
into two lobes, which fill up the variable angular space
between the femur and patella, being forced upwards from
below by the so-called flabelliform ligaments of the patella ;
an inferior free margin, also divided into two lobes, separated
* No. XXVII. of this volume.
ANATOMY OF THE KNEE-JOINT. 229
from one another by the attachment of the mucous ligament,
and which, in the nearly extended state of the joint, is pulled
back into the angular space between the condyles of the femur
and the tibial aspect of the articulation by the traction of the
mucous ligament ; and, in the flexed condition, is forced back-
wards by the pressure of the atmosphere.
The supra-patellar pad is adapted to a deep and charac-
teristic notch, which exists between the upper end of the
patella and the tendon of the quadriceps extensor. This would
appear to adapt the tendon to the bone in the varied antero-
posterior angular positions of the two parts during action.
The lateral patellar pad is the pouch-like fold which
sheathes the internal longitudinal facet of the patella.
The great and the supra-trochlear pads are situated, the
former at the upper and outer part of the great cul-de-sac of
the synovial membrane ; the latter, a larger external and
smaller internal, towards the upper part of the outer face of the
trochlea. These fill up the space between the patella and
the fore part of the femur above the trochlea in complete
extension.
I may conclude by adverting shortly to the remarkable
facetted configuration of the articular cartilages of the knee-
joint, a structure which has hitherto escaped notice. In
a previous part of this lecture the facets of the patella have
been described ; which bone, from the variable projections of
these facets, exhibits sometimes a concavity, sometimes a
convexity, and occasionally a flat profile.
On the surface of the tibial condyles the following facets
may be demonstrated : a semilunar facet on each condyle,
corresponding to the under surfaces of the semilunar fibro-
cartilages, and separated by faint but distinct blunt ridges
from a central femoral facet on each condyle, the latter in
contact with the femoral cartilage.
On the femur, in addition to the trochlea separated from
230 ANATOMY OF THE KNEE-JOINT.
the condyles proper by the oblique grooves, and presenting,
particularly in aged and slightly-diseased examples, traces of
the three successive stages in the position of the patella, there
are on the condyles semilunar tibial facets separated by faint
ridges, and in contact with the upper surfaces of the semilunar
cartilages, and uncovered portions, or femoral facets of the
tibia. On the inner condyle of the femur, and bounding the
oblique curvature, is the important crescentic facet already
described.
MECHANISM OF THE KNEE-JOINT. 231
X. ON THE MECHANISM OF THE KNEE-JOINT.*
THE physiology of the locomotory system, and especially that
of the joints, has been hitherto much neglected. Even in
Henle's elaborate System of Anatomy, now in course of publi-
cation, there is a lingering tendency to adhere to the formal
method of description ; and though presenting much freshness
and minuteness of description in his account of the articu-
lations, he has scarcely done justice to the results latterly
attained by the physical physiologists in this department
of the science.
The first step towards an anatomy of the joints adequate
to the physiology of the locomotory system that is, an
anatomy based on details affording data for precise mechanical
investigation was taken by Ed. and Wilh. Weber. f
As bearing on my present communication, I shall merely
indicate the more important results obtained by the Webers
in their examination of the knee-joint, as these appear to me
to involve the first germ of the correct conception of the me-
chanical constitution of the diarthrodial joints.
1. The knee-joint cannot be considered as a hinge-joint,
inasmuch as it does not present a fixed axis.
2. The femoral condyles roll, and at the same time glide,
like a wheel partially restrained by the drag, forwards in
* This paper was read in detail before the Koyal Society of Edinburgh,
January 18, 1858, but only an abstract was printed in the Proceedings of that
date. As the essay was found in its complete form amongst the author's
papers, we reproduce it here in extenso. EDS.
t Meckanik dcr Menschlichen Gehwerkzeuge : Gbttingen 1836.
232 MECHANISM OF THE KNEE-JOINT.
extension, backwards in flexion, on the nearly horizontal
surface of the tibia.
3. By a peculiar arrangement, certain ligaments become
tightened when the knee is extended, and the column or shaft
of the limb becomes rigid, and thus fitted more particularly
for the mechanical support of the body in its erect position.
4. The arrangement by which these ligaments become
alternately tightened and slackened, is the antero-posterior
spiral curvature of the femoral condyles ; the ligaments in
question being attached above to the neighbourhood of the
polar extremities of the curves, are consequently drawn up
and put on the stretch in extension, let down and slackened
in flexion.
5. The ligaments relaxed in flexion permit a rotation of
36 in the horizontal plane of the joint, during which the inner
condyle of the femur is comparatively fixed, while the outer
describes a curve, like the front-wheels of a carriage in pass-
ing round a corner. These observations of the Webers on the
knee-joint were published in 1836, but have in no respect
modified the current modes of viewing and describing this
important articulation.
H. Meyer published, in Miiller's Archivs for 1853, in the
course of a series of memoirs on the mechanics of the human
skeleton, his observations on the knee-joint. The most im-
portant features of this memoir are the observations on the
curvatures of the femoral condyles and on the axis of the
articulation. Viewing the patellar as distinct from the two
condyloid portions of the joint, he pointed out for the first
time a feature of the internal condyle of the femur which had
previously escaped notice in its proper form. The two pos-
terior thirds of this condyle are on the whole parallel to, and
of the same length as, the entire external condyle. The pre-
viously-recognised greater length, and so-called obliquity, of
the inner condyle, depends on the addition of a portion curved
MECHANISM OF THE KNEE-JOINT. 233
in a plane, oblique at once to the antero-posterior plane of the
condyle and to the horizontal plane of the joint, and inter-
calated "between the antero-posterior portion of the condyle
and the patellar surface. This intercalated portion may, ac-
cording to Meyer, be conceived as a segment of the base of a
cone, the vertex of which, in the erect position of the limb, is
situated in the external condyle of the tibia, with its axis
directed from above forwards and inwards, to below, back-
wards and outwards. The curve extends over 60, and the
axis of the generating cone inclined 45 to the horizontal.
This axis he distinguishes as the oblique axis of the joint,
and round it the leg and thigh are compelled to rotate, at the
close of extension and the commencement of flexion, when
the conical surface in question is in contact with the lateral
internal and anterior part of the inter-condyloid spine of the
tibia and the anterior crucial ligament.
Eeferring to the unsatisfactory character of the series of
co-ordinates on which the Webers based their assumption of
an equiangular spiral as the profile curvature of the femoral
condyles, Meyer concluded from measurements procured from
outlines of the curve made by means of a tracing-frame and a
telescope, that its posterior and anterior portions may be safely
assumed to be arcs of two circles, respectively 120 and 40,
.the radius of the former being to that of the latter as 5 to 9.
He conceives, therefore, that there are two transverse axes of
rotation in the knee-joint, an anterior and a posterior ; but
holds that, in treating the subject, one transverse axis only
need be assumed.
Whatever exceptions may be taken to Meyer's double
transverse axis, and to his assumed circular profile curve of the
femoral condyles, there can be no doubt of the general correct-
ness and great value of his observations on the so-called oblique
rotation of the joint, the corresponding arrangement of the
inner condyle, the coadjusted movements of the patella, and
234 MECHANISM OF THE KNEE-JOINT.
the harmonised attachments of the related muscles. It is
therefore somewhat remarkable that Henle, in his recent
work, should have referred to Meyer's researches only to deny
the specific character of the obliquely-curved portion of the
inner condyle.
I may here be permitted to state that, having been in the
habit, since I became a public teacher of anatomy, of explain-
ing the researches of the brothers Weber on the knee-joint, I
lost no time, after the appearance of Meyer's paper, in re-
examining the subject. An abstract of Meyer's observations,
with additional observations made by myself, were published
in a lecture in summer 1855, an abstract of which appeared
at the time.* I have since annually gone over the subject in
the University, and as the results in question bear essentially
on the more immediate subject of this communication, I shall
briefly enumerate them.
I obtained, then, satisfactory evidence that, as stated by
Meyer, the thigh and leg rotate in opposite directions at the
close of extension and at the commencement of flexion, and
that the co-ordinated arrangements for these movements, in
the patella, the ligaments, and muscles, are such as described
by him. But, in addition, I found that the cartilaginous sur-
faces of the patella, femur, and tibia, respectively, are not
continuous but facetted surfaces.
The patellar surface presents seven facets, which are in
no position of the joint, at the same time, all in contact
with the opposite femoral surface, nor can be made to fit it
throughout in any position of the opposite bones ; but come
into contact with that surface in a determined order of succes-
sion, which is invariable. The patellar surface of the femur,
as has been more particularly pointed out by Meyer, is sepa-
rated from the two condyloid surfaces by grooves ; but in
addition, I found that there are distinct marginal facets on the
* Edinburgh Medical Journal, July 1855 ; also No. IX. of this volume.
MECHANISM OF THE KNEE-JOINT. 235
condyles corresponding to, and rolling upon, the semilunar
fibro-cartilages ; and distinct from their remaining or central
portions, which are in contact with and roll upon the central
cartilaginous facets of the tibial condyles. The oblique curved
surface at the fore part of the inner condyle is a distinct facet,
which at the close of extension and at the commencement of
flexion moves upon and is in contact with the internal anterior
cartilaginous surface of the intercondyloid spine of the tibia ;
and with the tibial attachment of the anterior crucial liga-
ment ; and in extreme flexion is then, and then only, in contact
with one of the seven facets of the patella, which patellar facet,
in no other position of the joint, touches any other cartilagi-
nous surface, but is provisionally sheathed with a synovial
fold.
The two tibial condyloid articular surfaces also present
distinct semilunar facets, and central facets for the central
facets of the femoral articular surfaces.
In consequence of this facetted configuration, and the
peculiar curvatures of the opposite cartilaginous surfaces, the
latter are in no position of the joint coincident throughout ;
but gape more or less in different parts of their extent.
In addition to the previously-recognised function of the
semilunar fibro-cartilages as tough elastic structures for adapt-
ing the opposite femoral and tibial surfaces to one another,
the so-called Haversian glands, in addition to their lubricating
function, are arranged for a similar purpose. Every space or
gap between the opposite surfaces of the patella, femur, and
tibia, not provided for by the semilunar fibro-cartilages, is sup-
plied, when it appears, with an invariable, vascular, fatty
synovial pad, which is forced into the chink or pulled out
again by special arrangements ; and thus, not only do these
pads support, and render steady, the movements of the joints,
but lubricate the moving surfaces during action.
Since the publication of these results, I have annually
236 MECHANISM OF THE KNEE-JOINT.
devoted much attention to the configuration, movements, and
relations of the opposite cartilaginous surfaces of the diarthro-
dial joints. The details with reference to special articulations
I shall reserve for future communications ; at present I will
merely refer to certain general results, which bear more parti-
cularly on the mechanism of the knee-joint.
In all diarthrodial articular surfaces there are facets, more
or less pronounced, situated at the opposite extremities of the
lines of movement. These may be conveniently designated
terminal facets. They are not primarily engaged in guiding
or conditioning the movements, although they frequently
modify their initial and terminal portions. These terminal
facets are essentially surfaces against which, and on which,
the opposite bones come to rest.
The proper acting area in each of the opposite articular
surfaces is, after eliminating the terminal facets, comparatively
limited, and may generally be observed to present two facets.
These opposite facets act in pairs (a pair consisting of one on
each surface), acting together in the movement in one direc-
tion ; the other pair in the opposite alternate movement. The
pair of facets not in action break contact, or gape, during the
action of the facets engaged ; and the chink between them is
occupied by synovia or by a fatty pad.
But even the acting facets, during their movements, are
only partially in contact. They are only coincident when the
facets approach or have reached the limit of their movement
in their proper direction ; that is, when the flexion-facets
as they may be conveniently termed have completed flexion,
or when the extension-facets have completed extension. In
these latter stages of the movements of the acting facets, when
they come into contact, the corresponding terminal facets close
also. The acting facets may, even at the conclusion of their
proper action, break contact, and the entire joint rest on the
corresponding terminal facets.
MECHANISM OF THE KNEE-JOINT. 237
The movements of opposite diarthrodial surfaces on one
another appear to be in every instance a combination of
gliding and rolling ; the amount of gliding being directly, and
the rolling inversely, as the coincidence of the opposite arti-
cular surfaces.
An important addition has recently been made to our
conceptions of the mechanical constitution of joints, by the
nearly simultaneous publication of memoirs by Langer and
Henke, and of a report of these memoirs, with original obser-
vations on the same subject, by Meissner. As these new
observations refer principally to the ankle and elbow-joint,
and as I shall have afterwards to refer to them in detail, I
shall at present only allude to such points as bear on the
subject of this communication.
The important fact announced by these three observers is
the screw configuration of the articular surfaces of the elbow,
ankle, and calcaneo-astragaloid joints. The method of inves-
tigation adopted was to trace lines on one of the articular sur-
faces by means of a steel point passed a little beyond the
opposite surface previous to putting the joint through its
movements. These lines are termed " ganglinii" " go-lines,"
and in all the joints examined are arranged obliquely to their
axes of rotation. Langer, acting on the happy idea of pro-
longing the screw, by uniting in one direction a number of
plaster casts of the same articular surface, succeeded in form-
ing continued screws from the upper articular surface of the
astragalus in the horse, panther, and human subject.
Langer concludes that the " go-line" of the ankle-joint in
all the Mammalia is a portion of a helix, and that therefore
the astragaloid surface is a segment of a cylindrical or conical
male screw, while the tibio-fibular surface is a segment of the
corresponding female screw. The right ankle-joint is a left-
handed screw combination ; the left ankle-joint a right-
handed. When, therefore, the foot is conceived to be fixed,
MECHANISM OF THE KNEE-JOINT.
the leg, in passing from a position of extension to flexion,
moves laterally outwards along the axis of rotation, to an extent
which is directly as the amount of rotation and the sine of
the angle of inclination of the thread that is, in proportion
to the extent of flexion and the rapidity of the screw.
In attempting by Langer's method to develope these arti-
cular screw-models, I found, that when two casts were united,
an apparently satisfactory helix was produced. But, in adding
to the series, the spire diminished, and the helix closed on
itself. It appeared that not only the angle of inclination of
the thread, but also the radius of rotation, diminished. The
surfaces of two casts of the same articular surface could not
be accurately adapted to one another, even by placing them
together in the mould in which they were both cast. I found
that when one or the other of the lateral ridges which repre-
sent the thread of the screw was situated as a guide in joining
the models, the helix closed in one or the other direction.
In addition, I found that the models only fitted their moulds
in one position viz. that in which they were cast. This
follows from what already has been stated regarding the forms
of articular surfaces. The tibio-astragaloid articular surfaces
cannot therefore be segments of a cylindrical series. It appears
extremely probable that, abstracting the terminal facets, the
acting areas on each surface consist each of a segment of a
conical screw the convex portions of these two screws being
on the astragaloid, the concave on the tibial articular surface ;
the one screw coming^ into action in flexion, the other in
extension.
In following up the subject, I was compelled to re-examine
the knee-joint from this new point of view. It now occurred
to me, that instead of attempting to '''procure co-ordinates by
direct admeasurement of the articular surfaces, data for an
approximate conception of the forms of these surfaces in any
joint might be reached by tracing the path or locus of any
MECHANISM OF THE KNEE-JOINT. 239
distant point in one of the bones when in motion, or of the
point of a rod prolonged from it. I was enabled leisurely to
examine the path pursued by that point during flexion and
extension as projected on a plane parallel to the transverse
plane of the joint. The path described by the point of the
rod was found to be the same in both movements, but pre-
sented a form which cannot be referred to the movements of
the joint as hitherto conceived. It was a continuous curve,
which crossed that perpendicular line in the field of view,
with which the point of the rod in the extended position was
coincident, before it again came to rest in it at the close of
flexion. Supposing the leg to be fixed perpendicularly, what-
ever the nature of the profile curve described by the point of
the rod fixed in the axis of the thigh-bone during flexion and
extension whether cycloidal, if the profile curve of the femoral
condyles be circular, or some form of equiangular spiral, if
the condyles possess that character, it appeared evident that
the line projected on a plane parallel to the transverse plane
of the joint must be a perpendicular line. It also appeared
evident that if Meyer's rotation really occurred, the line pro-
jected on this transverse plane would be curved above and
pass below into a straight line. I found, however, on viewing
the point of the rod as projected in its course on this plane,
that the line was a continuous curve, concave throughout
towards the inner side in both the right and left lines.
It was evident, therefore, in the first place, that the upper
part of the curve was due to Meyer's rotation, renewed in
consequence of the obliquity of the shaft of the thigh-bone ;
and in the second place that the external condyle, and the
two posterior thirds of the internal do not roll and glide in
parallel planes, but along curved paths. But as the inner
condyle is rolling while passing round Meyer's curve, it is
clear that from first to last, in flexion and extension, the
condyles of the femur roll and glide along curved paths.
240 MECHANISM OF THE KNEE-JOINT.
This curve, being more leisurely examined by means of a
plumb-line suspended between it and the- eye, or through a
cross-threaded frame, or with a telescope with parallel wires in
the focus of its eye-piece, was found to be more rapid in its
curvature at the upper and lower end, while in the inter-
mediate portion of its extent it lay more in the direction of
the plumb-line.
It was now observed, on examining the joint itself, not
only that the condyles of the femur roll backwards and for-
wards in curved paths a fact which has hitherto escaped
notice but that this curvature or rotation is as strongly
marked at the flexion as at the extension extremity of the
movement.
By fixing the joint in the horizontal plane, and setting up
a series of rods from that plane to the point of the indicator
fixed in the femur, at equal intervals in its course, I have pro-
cured a system of co-ordinates which enable me by the eye to
trace more carefully the course of the curves on the three
planes on which it is projected. By this rough method,
altogether insufficient for precise results, the eye is nevertheless
enabled to detect 1. That the line is a helix, with variable
curvature, with a more rapid sweep at its upper and lower
portions than in the intermediate distance, the upper sweep
being the larger of the two ; 2. That there are two breaks in
its course, the first near its upper end at the commencement
of the great sweep, and most perceptible in the mesial plane ;
the second is situated about the junction of the lower and
middle third of the line, and consists of an angular bend, with
a more rapid curvature on each side, observable in the mesial
and transverse planes.
These peculiarities in the curve induced me to re-examine
the curvatures of the femoral condyles, and I found that the upper
break corresponded to the grooves between the patellar and
condyloid surfaces, and also recognised what has also hitherto
MECHANISM OF THE KNEE-JOINT. 241
escaped notice, that a little behind the middle of the profile
curvatures of the femoral condyles, and more particularly on
the outer condyle, there is an angular break, in front of and
behind which the curvature is more rapid. Tracing the posterior
curvature backwards from the break at the outer edge of the
external condyle, where its position is indicated by a tubercle
about the middle of the popliteal notch, it passes backwards
along the condyloid margin, and also obliquely backwards and
inwards into the hitherto unnoticed prolonged superior pos-
terior internal angle of the condyle. The portion of the inner
edge of the outer condyle corresponding to the posterior part
of the curve now in question is concave inwards, and is the
margin of the space for the superior attachment of the
external crucial ligament, as the outer margin of Meyer's
curve limits the space for the attachment of the internal
crucial ligament. Within these limits the curve of the pos-
terior area of the condyle diminishes backwards, so as to
give it the appearance of a conchoidal surface. The posterior
area of the inner condyle and its curves are equally appreciable,
but flatter and less distinctly marked.
The anterior area with its curve is most fully developed
on the inner condyle. The outer part of this area is the facet
previously mentioned in my reference to Meyer's oblique axis.
It limits the attachment of the posterior crucial ligament, and
its curvature diminishes from before backwards. The anterior
area on the external condyle, like the posterior on the internal,
is flatter, shorter, and less fully developed.
The helicoid character of the curve of movement appeared
to me to indicate a screwed structure in the joint. The cha-
racters of the portions of the curve before and behind the
posterior break, and the corresponding and remarkable
peculiarity of the condyloid areas and their curves, taken along
with what I had already observed in the ankle, led me to
suspect that the movements of the knee-joint are combined
R
242 MECHANISM OF THE KNEE-JOINT.
gliding and rolling movements of conical screwed surfaces
upon one another. To adapt this hypothesis to the structure
of the joint and the general character of the curves, it was
necessary to assume that the anterior areas of the combined
femoral condyles are portions of a double-threaded conical
nut ; the anterior parts of the combined tibial condyles, and
the corresponding part of the intercondyloid spine, with other
structures to be afterwards mentioned, are portions of a cor-
responding double-threaded conical tap. It was also necessary
to assume that the combined posterior areas of the femoral
condyles are portions of a second conical nut, and the com-
bined posterior portions of the tibial condyles and spine the
corresponding tap. The hypothesis, however, in addition re-
quired that the anterior screw-combination should be opposed
to the posterior ; if the anterior is a right-handed, the pos-
terior must be a left-handed screw.
In the absence of numerical values for the co-ordinates of
the curves (which, however, I do not despair of procuring), I
cannot make a definite statement ; but the general character
of the curves observed, and the corresponding movements and
structure of the joint, leave little doubt in my mind that the
flexion and extension, combined gliding and rolling movements
of the knee are performed between two conical double-threaded
screw-combinations, an anterior and a posterior the anterior
being a left-handed screw, and the posterior a right-handed
screw in the right knee-joint ; the anterior a right-handed,
and the posterior a left-handed screw in the left knee-joint.
The movements which take place round these two com-
binations are alternate those round the anterior completing
extension and commencing flexion ; those round the posterior,
completing flexion and commencing extension of the joint.
The movements round the anterior combination are more
extensive and important than those round the posterior ; and
in the ordinary use of the joint are alone employed.
MECHANISM OF THE KNEE-JOINT. 243
The result of these two combinations is, that in complete
extension the anterior combination is screwed home, while
the posterior is unscrewed. In complete flexion, again, the
anterior combination is unscrewed and the posterior is home.
For the purpose of understanding how the screw-movements
of the femur and tibia round two axes alternately, both of
which are only slightly, if at all, inclined to the axis of the
limb, should result in the so-called flexion and extension at
the knee, it is necessary to consider some of the properties of
conical screws, and of the peculiar modification of them which
is presented by the mechanism of the knee-joint. A conical
screwed nut and tap, if both constructed of comparatively
unyielding materials, do not coincide, and consequently do
not afford any serviceable result as a screw-combination till
they have been screwed home. Conical screw-combinations
are consequently rarely employed in the arts ; and when they
are made use of, the male or female screw, more generally the
latter, consists of a yielding, elastic, and tough material. The
opposed threads of a conical screw-combination constructed of
such materials are throughout congruent with one another ;
and that amount of friction consequently procured, which
constitutes an element of the productive effect of a cylindrical
screw-combination ; and the total absence of which renders a
conical screw-combination of unyielding materials inefficient
till screwed home. In the knee-joint the concave screws on
the articular femoral surface are comparatively unyielding ;
while the convex screws $n the tibial surface are only par-
tially cartilaginous, but mainly flexible, elastic, and tough.
Their movements, therefore, are precise, and when screwed
home the opposite elements of each combination become fixed.
In screwing and unscrewing a conical combination of unyield-
ing materials up to the completion of the one process, and
from the commencement of the other, the concave and convex
screws are non-coincident. Both processes may be conceived
244 MECHANISM OF THE KNEE-JOINT.
as being accomplished without any contact of the opposite
surfaces up to the completion of the one and from the com-
mencement of the other ; and the contact takes place simul-
taneously all over from base to vertex in the one case, and is
as simultaneously broken in the other. However irregular
the movements may be by which a conical screw-combination
may be screwed on or off, there is one general direction by
which the movements must be guided namely, a rotation of
one or other, or of both screws in opposite directions, round
the common axis of the system. The amount of this rotation
will be directly as the rapidity of the thread in any given
combination ; but, however rapid the thread may be in any
such combination, there must always be a certain amount of
rotation to admit of complete separation of the two elements.
It is evident, therefore, that in the application of a conical
screw- combination in the construction of a joint required to
move in flexion and extension, the most advantageous direc-
tion in which the axis of the combination could be placed
would be coincident with the axis of flexion and extension,
and the most disadvantageous that which most nearly opposes
the axis of the limb -; for if coincident with that axis, there
would be no apparent hinge-movement at all. We have
exemplifications of the permissible limits of such an arrange-
ment in the elbow and knee joints. In the former the axis of
the screw is nearly at right angles to the axis of the limb ;
in the latter, nearly coincident with it.
The arrangements by which the screw-combinations at the
knee-joint are adjusted for the general movements of flexion
and extension are as follows : The diameters of the funda-
mental cones considerably exceed their vertical height. They
are double-threaded, deep cut, with an obliquity of thread so
proportioned to the cone that they form little more than half-
spires. The upper portions of the taps of these screw-systems
consist of ligamentous texture (crucial ligaments), the basal
portions of bone and cartilage (tibial condyles and spine),
MECHANISM OF THE KNEE-JOINT. 245
the lateral parts of fibro-cartilage and ligamentous texture
(semilunar discs and lateral ligaments). The nuts consist of
corresponding portions of the femoral condyles. There is
actually retained, however, for the service of the joint, only so
much of each combination as is necessary for the required
movements. The base of the tap is connected to the vertex
of the nut by the crucial ligaments, which form the apex of
the former, and when the combination is screwed home these
ligamentous bundles are in a state of tension. In the process
of unscrewing, the ligamentous bundles of the tap become, on
account of their mode of attachment to the vertex of the nut,
successively relaxed from the point downwards ; while this
graduated relaxation of the ligaments provides for the tension
necessary for the continued gliding screw-movement. The
successive relaxations of those ligamentous bundles, which,
having served their purpose, are no longer required, permit a
movement to be superadded to this form of organic screw,
which the artificial screw does not admit of. The relaxation
of the vertex of the tap permits the two threads of the nut to
roll as well as glide along. The nut rolls as well as glides on
its convex condyloid surfaces. But as only a limited extent
of the cartilaginous surface of the tap is adapted to the carti-
laginous surface of the nut, the latter would speedily roll and
glide off the former, if the latter were not prolonged in the
required direction. The rolling movement of the convex
margin of the nut is further provided for by the interposition
of the tough and elastic semilunar discs ; as, moreover, the
rolling motion increases from the axis to the periphery of the
combination, it takes place principally on these discs, while
the gliding or proper screwing motion, increasing proportion-
ally towards the axis, takes place chiefly between the opposite
cartilaginous surfaces of the central part of the condyles of
the two bones, and to the greater extent between the central
margins of the femoral condyles and the surface of the spine
of the tibia.
246 CURVATURES AND MOVEMENTS OF THE
XI. ON THE CUEVATUEES AND MOVEMENTS OF
THE ACTING FACETS OF AETICULAE SUEFACES. *
1. THE opposite gliding surfaces of joints employed by me-
chanicians are surfaces of revolution ; and consequently all
sections of these surfaces, at right angles to their axes of
rotation, are circular arcs. In all uncompounded artificial
joints, therefore, except those with spherical surfaces, the
movements are limited to rotation in opposite directions round
a single axis.
2. In organic joints, on the contrary, the opposite gliding
surfaces are not surfaces of revolution ; they are not cylindrical,
conical, or spherical, in the geometrical sense of the terms.
In no instance, as far as I have observed, is a section at right
angles to the assumed or so-called axis of rotation, the arc of
a circle ; nor, as it appears to me, is it possible to associate
the characteristic curvature of the path described by a given
point in the bone or limb to which the joint appertains, with
articular surfaces of revolution.
3. As stated in my former communication " On the Me-
chanism of the Knee-Joint,"t the opposed surfaces of organic
joints are not continuous but faceted areas ; and of the
various kinds of facets indicated by me as existing on opposite
articular surfaces, those termed " acting facets" determine the
movements of the bones to which the joint appertains, and
* This memoir had evidently been carefully prepared for publication, but
had not been sent to press. It is now published, therefore, for the first time.
EDS.
t Proc. Royal Soc. Edinburgh, Jan. 18, 1858 ; and No. X. of this volume.
ACTING FACETS OF ARTICULAR SURFACES. 247
are consequently the fundamental facets of the articular
areas.
The object of the present communication is to put on re-
cord the general result of the observations I have made on
the configuration and movements of central articular facets
since the date of the paper above referred to ; and to submit
a theory of their probable geometrical character.
4 The central facet on one articular area of a joint is
adapted to a corresponding central facet on the corresponding
opposite articular area of that joint. The surface-curvatures
of the two facets are similar, so that the facets themselves may
be considered reciprocally as cast and mould of one another.
I shall have occasion hereafter to employ the term articular
couple to designate collectively two opposite corresponding
facets of any kind ; and the individual facets of such couples
I shall term twin-elements.
5. The twin elements are not invariably developed to the
same extent, one of them being generally only a portion of the
entire facet, the deficient portion being supplied by yielding
and elastic structure, and which may be replaced in the exa-
mination of certain joints by a cast in wax or plaster of the
corresponding portion of the opposite facet. This restriction
or curtailment of one of the twin elements is referable to that
principle of constructive economy which is evinced in the
arrangements of organic mechanism, in the midst of their
general complexity ; and it will, moreover, appear in another
section of this communication that the retention of the whole
of both the twin elements is not essential to their peculiar
mode of action. I find it convenient to employ the terms
reserved and restricted to distinguish the articular elements in
these respective conditions.
6. If the two elements of an articular couple be observed
during action, they will be seen to glide past one another in
two directions in such a manner that, assuming both of them
248 CURVATUKES AND MOVEMENTS OF THE
to be complete i.e. unrestricted and therefore congruent or
in contact throughout at the commencement of action, the
congruence becomes a minimum at the close of action ; and the
twin elements may even be completely separated from one
another in the subsequent movements of the joint. The two
movements are simultaneous, so that the actual movement is
their resultant.
*7. The two movements determine the contours of the
facets. The most extended movement, which determines the
length of the facets, I shall term the primary movement, or
(for reasons to be afterwards stated) the movement along the
thread. The two extremities of the facets will be referred to
as proximal and distal. The other movement I shall term
secondary, or the movement across the thread. This movement
determines the breadth of the facets and their two margins
respectively; subject, however, like the lengths and extremities
of the facets, to the restrictive modification of the two margins
of each element respectively, the one has a higher teleological
import than the other. I shall refer to the former as the
proximal, to the latter as the distal, margin.
8. When, therefore, the elements of a couple are in their
fundamental positions i.e. when they are in contact through-
out their extremities and margins are also coincident respect-
ively ; but in consequence of the frequent restriction of por-
tions of one element, the corresponding portions of the other
are not in contact with correlative portions of surface, but with
synovia, synovial pads, or elastic menisci.
9. The lines of the thread, or of primary movement, which
extend from the proximal to the distal extremities of the
facets, are curves of double curvature of a helical form. The
curvature of these lines, while maintaining its general cha-
racter throughout, diminishes in extent or sweep, appearing
more rapid as it approaches the proximal extremities of the
facets ; and therefore I distinguish the proximal extremity of
ACTING FACETS OF ARTICULAR SURFACES. 249
a facet by the more limited sweep and apparently greater
rapidity of its longitudinal curvature.
10. It is evident, therefore, that these helical lines of cur-
vature cannot be conceived as developed on a cylindrical
surface ; they must lie in some surface of a conical form.
The lines may, however, be provisionally assumed as conical
helices of a given curvature.
11. The lines of movement across the thread are also curves
of double curvature. The curvature of these transverse lines,
like that of the longitudinal, while it maintains its character
throughout, is more limited in extent, with less sweep, and
therefore apparently more rapid as it approaches the proximal
margins of the elements. The transverse lines also have
their centres of curvature towards the proximal extremities
of the facets. The concave margin also is of less extent than
the convex, and the proximal extremity narrower than the
distal.
12. It also follows that the margins of the twin-facets
must be concave towards the centres of longitudinal curva-
ture i.e. the marginal outlines of the two facets respectively
must be, as they are in fact, concave on one side, convex on
the other.
13. As already stated, the actual movement of the twin-
elements of an articular couple is the resultant of their
primary and secondary movements. This resultant movement
may be effected by either of the two elements on the other, or
by both simultaneously. The resultant or actual movement
of an articular couple occurs alternately in opposite direc-
tions along the same path ; when completed in one direction
the articular elements are in a maximum of contact ; and
when the movement is repeated in the opposite direction,
they are in the position of minimum contact. I find it con-
venient, in treating of the movements of joints, to employ the
terms positive and negative for the two opposite relative posi-
250 CURVATUllES AND MOVEMENTS OF THE
tions of maximum and minimum contact of their constituent
articular couples. In the positive position, an articular couple
is in a state of stable equilibrium. In the negative position it
is in the condition of unstable equilibrium.
14. If the successive relative positions of the twin-ele-
ments of a couple are examined in series from their positive
to their negative phase, it will be observed that as the
proximal extremity of the one element glides towards the
distal extremity of the opposite element, the corresponding
margins of the opposite elements glide past one another ; so
that when the negative phase is attained it will be found that
the proximal portion only of the distal extremity of the one
element remains in contact with the distal portion only of the
proximal extremity of the other element. During the return
movement from the negative to the positive phase, the series
of successive relative positions is reversed ; thus the opposite
extremities and margins glide towards one another, so that
at the close of the movement the proximal portion of the
distal extremity of the one element, which in the negative
phase is in contact with the distal portion only of the
proximal extremity of the other element, now resumes its
original positive position, while the margins have also be-
come coincident, and the twin-elements consequently con-
gruent. The movement is thus of such a kind that in the
passage from the positive to the negative phase the cor-
responding extremities and margins of the twin-elements
recede from one another, until at last the proximal part of the
distal 'extremity, and the contiguous part of the proximal
margin of the one element, coincide with the distal part of
the proximal extremity and the contiguous part of the distal
margin of the opposite element.
15. As already stated (13), when the couple is in the
positive phase its elements are in stable equilibrium ; so it
may now be observed that the only mode in which they can
ACTING FACETS OF ARTICULAK SURFACES. 251
pass from the positive to the negative* phase without losing
entirely their stability is by a combination of the primary and
secondary movements for any attempt to glide the one
element over the other, except by the double movement, im-
mediately destroys the congruence of the couple. It will also
be observed that the twin-elements, when in their positive
position, are fixed or adjusted in their proper localities ; and
that the successive extents of congruence during the action of the
couple are directly as the approximation to the positive, and
inversely as the approximation to the negative phase.
16. The successive extents of congruence appear to be
determined by the successive adaptation of corresponding por-
tions of curvature on the opposite elements, as these elements
pass through their opposite movements ; for it appears as if
the gliding of the twin-elements across the thread not only
successively accommodates their transverse, but also their
longitudinal lines of curvature as they respectively meet one
another.
17. During the gliding in the lines of the transverse cur-
vatures in passing from the positive to the negative phase,
the two bones on which respectively the twin-elements are
situated gradually incline on one another towards that side of
the articular couple on which the proximal margins of the
elements are situated. As it will appear in the sequel that in
some couples the proximal margins are on the concave, but
in others on the convex sides of the couple, the inclination of
the two bones will be to the concave side in the former, to
the convex side in the latter.
18. During the gliding in the lines of longitudinal cur-
vature in passing from the positive to the negative phase, the
two bones incline towards the distal extremity of the couple
if that couple has a concave proximal side, and towards the
proximal extremity of the couple if that couple has a convex
proximal side.
252 CURVATURES AND MOVEMENTS OF THE
19. From what has now been stated, it is evident that the
two bones return to their original positions as the couple
resumes its positive phase. We may, therefore, assume a
straight line passing through the surfaces of the couple, or a
parallel to such a line, as representing the two bones in their
relative positions to one another in the positive phase of the
couple. At the commencement of the passage to the negative
phase, the line separates into two portions at the point where
it passes through the twin-surfaces ; and these two portions
thenceforward to their negative position assume a series of
relative positions determined by the resultant movements
of the twin-elements. These series of relative positions must
be similar, but necessarily in inverse order, during the return
to the positive phase.
20. As already stated, the longitudinal and transverse
lines of curvature of the twin-elements are curves of double
curvature ; and as the resultant movements of the ele-
ments themselves must be helical, it follows that the two
halves of the line representing the two bones must pass
through a series of positions of such a kind that, during
action, any given and corresponding point in each of these
lines will describe a helical path of similar but opposite cur-
vature.
21. The geometrical character of the generative curves of
an articular couple can only be finally determined by means
of numerical data. As, however, the forms and movements
presented by the twin-surfaces exhibit throughout these
strongly marked already described distinctive characters, it
becomes a matter of importance to inquire whether the
conditions of these characters are fulfilled or supplied by any
one geometrical curve.
22. With this object in view, it is to be observed that
during the double gliding of the elements upon one another
in their alternate passages from their positive to their nega-
ACTING FACETS OF ARTICULAR SURFACES. 253
tive, and from their negative to their positive positions, a
progressively diminishing or increasing extent of congruence
appears to be provided for ty the successive gliding into apposi-
tion, and therefore into congruence, of geometrically-similar , as
well as linearly-equal portions of curvature not previously
coincident.
23. In other words, the geometrical arrangement of the
surfaces of the opposite elements appears to be such as will
provide, not only for their perfect congruence when in their
positions, by means of geometrically-similar and linearly-equal
longitudinal and transverse lines of curvature fitted into one
another in the- opposite elements, but also for an alternating
series of progressively diminishing and increasing extents of
congruence, by means of corresponding series of geometrically-
similar and linearly-equal portions of longitudinal and trans-
verse curvatures on the opposite elements, and increasing or
diminishing in accordance with the positive or negative direction
of the movements. These successive coincidences of these
similar and equal portions of longitudinal and transverse
curvature being brought about by corresponding gliding move-
ments in the negative and positive directions.
24. The equiangular spiral, in its more general form as a
curve of double curvature, is the only geometrical curve which
fulfils the conditions of the successive movements and adap-
tations of articular curvatures now under consideration. A
characteristic property of this spiral, and one which peculiarly
adapts it for generating the curvature of the surfaces of organic
joints, is the geometrical similarity of all portions of any given
example of curve which subtends the same polar angle, how-
ever different their linear dimensions may be ; so that, if the
spiral be conceived as revolving round its pole, in the plane
of two lines diverging from the pole, the lines will inter-
cept an infinite number of geometrically-similar portions of
the curve, but which become infinitely smaller or greater as
254 CURVATURES AND MOVEMENTS OF THE
the curve advances in the direction of its pole or away
from it.
25. Now we may conceive the opposite, similar, and equal
curved surfaces of an articular couple to be generated simul-
taneously by a given equiangular spiral. This spiral, in
successive stages of development, represents corresponding
successive transverse lines of curvature of the twin-elements ;
its primitive extent or dimension being assumed as equal to
that of the first opposite transverse lines at the proximal
extremities of the elements. The proximal extremities of the
transverse lines of curvature, which collectively constitute the
proximal margins of the elements, are assumed as representing
the polar portion of the generating curve; while the distal
extremities of the transverse lines of curvature, which collec-
tively constitute the distal margins of the elements, are as-
sumed as representing the anti-polar portion of the generating
curve. The primitive dimension of the given curve having
been assumed equal to the first proximal transverse curvature
on each element, the successive greater transverse curvatures
are geometrically conceivable as being produced by successive
rotations of the generating curve round its pole and in the
direction of the pole, so that successive additions are made
to its anti-polar extremity, and consequently to the distal
extremities, of the transverse lines of curvature of the
anti-polar elements.
But it is evident, on inspection of the articular surface of
an acting couple, that the transverse lines of curvature are
arranged in series along the lines of longitudinal curvature,
and that the series therefore sweeps in a helical or screwed
direction round a central axis of the entire combination. We
must assume, therefore, in addition, that the generating spiral,
while increasing its dimensions by revolving round its pole
in the direction of that pole, also revolves tangentially round
a fixed axis, while it glides along that axis in the direction of
ACTING FACETS OF ARTICULAR SURFACES. 255
its length. If, now, the generating spiral increases its dimen-
sions, so that each linear increment corresponding to a given
angular increment shall vary as the existing dimensions of
the spiral itself, then the longitudinal curvatures of the sur-
faces developed that is, the lines of curvature resulting from
the revolution of the continually-increasing generating spiral
round, and the gliding of it along, the fixed axis, must also be
equiangular spirals, with a constant ratio determined by that
of the generating spiral.
26. The opposite surfaces, thus simultaneously generated,
would evidently be congruent screwed surfaces, representing
respectively the concave and convex elements of a conical
screw-combination. The curvature in the direction of the
thread of such a screw-combination would possess the cha-
racter of the equiangular spiral ; while the curvature across
the thread would possess corresponding characters.
27. It is evident that the concave and convex elements of
a screw combination of this kind would be fully congruent
when in apposition, and that their axes would be coincident.
It is also clear that any attempt to unscrew a combination
of this kind, while the axes of its two elements are retained
in a right line, would at once render its entire opposite sur-
faces incongruent, in fact separate them from one another.
If, on the other hand, it were possible to diverge the axes of
the two elements from one another at the same time that the
elements are unscrewed, then there would result from these
combined movements a gliding of the opposite surfaces upon
one another over a succession of extents, which would
diminish in area in terms of the constant ratio of the generat-
ing spiral, until finally a minimum of contact of congruence
would obtain that is, to use the terms already employed,
the screw- combination would be in its negative phase, and its
elements in their negative positions. On reversing the com-
bined movements that is, on screwing the combination into
256 CURVATURES AND MOVEMENTS OF THE
its stable or positive phase the two elements would glide on
one another over successive extents of congruence or contact,
which would increase in dimensions in terms of the constant
ratio of the generative spiral, until both surfaces become con-
gruent throughout i.e., until the elements are again in their
positive positions.
28. The combined movements i.e. 9 the movements along
the thread, and the inclination and consequent divergence of
the axis of the elements, or, what is equivalent, the move-
ment across the thread are only possible under the condition
that the structure of the combination shall consist of rigid
materials, along a limited extent only of a single spire or
whorl, so that the movements on that side of the whorl shall
not be counteracted by those on the opposite side. It is this
condition of applicability which determines the comparatively
small extent of whorl in the greater number of articular
couples, and more especially in their restricted elements.
29. The combined movements being thus provided for,
the successive longitudinal and transverse adaptations must
occur in the following order : The elements being in their
positive phase, it is evident that during the passage to the
negative phase successive transverse curvatures in the one
element must pass off and become unscrewed at the proximal
extremity of the couple ; while at the same time successive
transverse curvatures of the opposite element must be left
uncovered at the distal extremity of the couple. With
regard to the mode of adaptation of those successive portions
of the elements still in contact or covered by one another, it
is to be borne in mind that the successive transverse curva-
tures are successive developments of a given extent of a given
equiangular spiral ; they are all, therefore, geometrically dis-
similar, as well as linearly unequal ; but from the law of the
equiangular spiral, every greater development of a given
extent of curve contains a portion geometrically similar and
ACTING FACETS OF ARTICULAR SURFACES. 257
linearly equal to every lesser development of it. And as all
these geometrically-similar and linearly-equal portions of
curvature are, from the assumed relations of the generating
spiral, necessarily collocated in a regular series along the
two elements of the couple, it follows that in the passage from
the positive, to the negative phase, each greater transverse curva-
ture, when it advances on the next opposite lesser curvature,
cannot coincide with it as a whole, but "by the transverse gliding,
as much of its polar extremity as is geometrically similar and
linearly equal to that next opposite lesser curvature will coincide
with it, while the remaining portion of its antipolar extremity pro-
jects uncovered leyond the antipolar extremity of the lesser. The
same relations subsisting between all the other greater trans-
verse curvatures of the one element, and those next lesser
transverse curvatures on the opposite element, all the remain-
ing transverse portions of linear coincidences go on dimi-
nishing, in terms of the common ratio of the generating curve,
until the negative phase is reached, or loss of contact occurs.
On reversing the combined movements during the passage
from the negative to the positive phase, portions geometrically
similar, and linearly equal transverse curvatures, increasing
in terms of the common ratio, successively coincide ; while the
proximal and distal extremities of the twin-elements respec-
tively approach one another, and their distal margins approxi-
mate till complete congruence is again attained.
30. It is evident that the principle, which provides for a
succession of progressively diminishing, or increasing, portions
of similar and equal transverse curvature, involves a corre-
sponding series of progressively diminishing or increasing
similar and equal portions of longitudinal curvature, and
consequently a resultant series of progressively diminishing,
or increasing, similar and equal areas of curved surface for
contact on the opposite elements of the articular coupla
31. It is also evident that we may assume the generating
s
258 CURVATURES AND MOVEMENTS OF THE
spiral, as it simultaneously glides along and revolves around
the axial line, to do so with its polar extremity directed either
towards or away from that axis. In the former case, the
proximal or polar margins of the resulting elements will
constitute the concave side of the couple, which will be con-
sequently directed towards the axis. In the latter case, the
polar or proximal margins of the resulting elements will
constitute the convex side of the couple, and will therefore be
turned away from the axis. These two forms of articular
couples are therefore also respectively distinguished by the
direction of their secondary or transverse gliding ; when the
polar side of the couple is concave, or towards the axis, the
transverse gliding of the elements, during their passage from
the positive to the negative phase, is such as that the inclina-
tions of the two portions of a right line passing perpendicularly
through the couple will be towards the axis, and away from
it on the return from the negative to the positive. When, on
the other hand, the polar margins of the elements are on the
convex side of the couple, the elements glide in such a
manner that the two halves of the perpendicular line incline
away from the axis, and towards it on the return to the posi-
tive phase. As the collocation of these two forms of articular
couples constitutes an important feature in the construction
of certain joints, and as they demand therefore distinct
designations, I shall employ the term axial to indicate a
couple the proximal side of which is towards the axis, and
the term antaxial to indicate a couple the proximal side of
which is convex.
32. In certain joints, each articular couple acts in concert
with a second articular couple, which is developed around the
same axis, but on the opposite side. Tor this arrangement I
shall employ, as in my former communication on the knee-
joint, the term articular combination. If we assume, as I
have done throughout the present communication, that the
ACTING FACETS OF ARTICULAR SURFACES. 259
generating curve of articular couples is in each instance a
special equiangular spiral, we may conceive the two constitu-
ent couples of an articular combination to be simultaneously
generated by two similar and equal equiangular spirals placed
tangentially on opposite sides of a common axis, but with the
polar extremity of the one, and the antipolar extremity of
the other, in contact with it, so that all tangentially-corre-
spending parts in the generative curves of the two couples
shall be parallel, while they at the same time glide along the
axis and revolve around it in the same direction, increasing
their dimensions by successive increments in a given ratio at
their antipolar extremities, by revolving round their poles in
the direction of these poles. The two couples thus generated
would be respectively axial and antaxial, the former having
the pole of its generative spiral towards, the latter turned
away from, the common axis. During the passage of a com-
bination of this kind from its positive to its negative phase,
the opposite elements of both of its couples would respectively
glide in the same direction along their threads, because
the proximal and distal i.e., the polar and antipolar ex-
tremities of the couples are symmetrical, But as by construc-
tion the one couple is axial, and the other antaxial, their
margins are not symmetrical, for the polar margins of the
axial couple are on the concave, those of the antaxial on its
convex side. But this asymmetrical arrangement of the
margins of the two couples of the combination necessarily
co-ordinates their gliding across their threads. Their com-
bined movements across their threads and their inclination in
relation to the axis being simultaneous, and all their geo-
metrical relations being similar and equal e.g., all tangents
of corresponding points in their curvatures being parallel,
as the same relations obtain during the passage of the com-
bination from its negative to its positive phase it follows that
a combination of this kind could be screwed and unscrewed
260 CURVATURES AND MOVEMENTS OF THE
with increasing and diminishing series of contacts, and in the
same manner as a single couple ; but with this advantage, that
while the single couple, in its negative phase and in its minor,
degrees of contact, is supported on one side only of the axis,
an articular combination is supported by two equal contacts
on opposite sides of the axis. An articular combination is in
fact equivalent to a double-threaded screw, as a single articular
couple may be conceived as a single-threaded screw.
33. The theory of the geometrical development of articular
surfaces, which I have endeavoured to express in this com-
munication, necessarily involves the possibility of dexiotrope
and scceotrope i.e., right and left-handed articular couples and
combinations. The two forms depend upon the direction in
which the generative curve revolves around the axis, moving
with the hands of a watch to the right in a dexiotrope,
against the hands of a watch in a scseotrope couple or combi-
nation. We find accordingly that the corresponding articular
couples and combinations on opposite sides of the body are
opposed to one another in the direction of their winding.
Thus, for example, it was pointed out in my former communi-
cation (p. 242) that the anterior articular combination in the
knee-joint is left-handed in the right knee and right-handed
in the left, and that the same relations obtain in the posterior
articular combinations of opposite knee-joints. In succeeding
communications I will point out that articular combinations
with opposite windings, on opposite sides of the body, similar
to those in the knee-joint, exist in the ankle and tarsal, and
in the elbow and carpal joints ; and that the hip and shoulder
joints consist of single-threaded couples, but also with opposite
windings on opposite sides of the body.
34. The nature of that more or less marked restriction or
curtailment of one or both elements of a couple, already
adverted to in paragraph 5, may now be more fully examined.
This restriction or curtailment consists essentially in the
ACTING FACETS OF ARTICULAR SURFACES. 261
elimination or removal of such portions of one or both of the
elements in their typical form (that is, in the forms which
they would possess in virtue of their completed geometrical
construction), as are not absolutely essential to their efficient
action. Thus, for example, as one essential condition of
efficiency of an articular couple is the provision of a sufficient
extent of perfect contact in the negative phase, an articular
couple would act efficiently, although the whole of the proxi-
mal margin of one of the elements were removed, along with
as much of the remaining portion of that element as would
retain in reserve enough of the proximal extremity of its dis-
tal or antipolar margin for contact, during the negative phase,
with the distal or antipolar portion of the polar margin of the
opposite element ; or, expressing the matter in less precise but
more direct terms, the couple would act efficiently as regards
its passage to its negative phase, although only the polar or
proximal extremity of one of its elements were reserved, and
the place of its removed portion supplied by soft, yielding,
or elastic textures. It is obvious, however, that if only the
polar portion of one of the elements be retained, a certain ex-
tent of the opposite element may be dispensed with namely
the distal and antipolar portion of its distal margin. Both
elements of a couple may, therefore, be more or less restricted;
but as, however much the polar margin of the one element
may be curtailed, the corresponding margin of the opposite
element must be reserved, I employ, as stated in paragraph
5, the term restricted to designate the element with the cur-
tailed, and the term reserved to designate the element with the
retained, polar margin. As the object of the present com-
munication is to record the general principles involved in the
inquiry, I reserve for succeeding communications on special
points all details relating to articular elements, couples, and
combinations, as well as their relative adjustments by means
of ligaments, nbro-cartilaginous menisci, and synovial pads.
262 CURVATURES AND MOVEMENTS OF THE
35. It appears necessary, however, at this point to anticipate
so far by recording a few observations on the teleological re-
lations or final purposes of these peculiar principles of con-
struction which characterise organic joints.
From the peculiar character of the curvature which obtains
in organic joints, all points of their opposite surfaces come
successively into and then break contact, so that these joints
perform a maximum of work with a minimum of surface-
contact ; while, at the same time, that weakness which is en-
tailed by diminution of surface-contact on the organic as well
as on artificial joints, is compensated for by muscular action
in the former during its movements to and from its negative
position, whereas the latter must in all its positions support
itself. Both the organic and the artificial joints derive ad-
vantage from diminished surface-contact, for their deterioration
is lessened by the diminished amount of pressure and friction.
But the deterioration of the materials and structure of an
organic joint during action may be assumed as proportionally
greater than that of an artificial joint, for in addition to the
actual injury to structure sustained, there is, during action, a
suspension more or less complete of those nutritive processes
on which the ulterior integrity of the organic joint surface
depends. The artificial joint surfaces consist of materials
which may be assumed as not subject to deterioration of their
molecular constitution, but only in their configuration during
action from pressure and attrition. This deterioration cannot
be remedied by the economy of the joint, but accumulates
with duration of action, and ultimately demands the interfer-
ence of the mechanician. The organic joint surfaces again
not only suffer from pressure and attrition, but in their
molecular constitution as well, and as this molecular deterio-
ration diminishes the efficiency of their ulterior action, the
organic joint is subjected to more speedy injury in the per-
formance of its function than the artificial.
ACTING FACETS OF ARTICULAR SURFACES. 263
But this liability of the acting surfaces of an organic joint
to molecular deterioration during action, while it would sub-
ject the joint to greater injury from a given amount of work
than an artificial joint, is compensated for by the curvature of
its articular surfaces, which provides for that amount of time
necessary for successive restorations in the intervals of suc-
cessive contacts. For to whatever extent the opposite surfaces
of an artificial joint may be diminished, there must always
remain a certain extent of its opposite surfaces in contact ; and
from the circular form of the transverse section, the successive
amounts of contact, corresponding to a series of equal changes
in angular position during rotation, must be in arithmetical
progression. But in the organic joint the successive amounts
of contact, corresponding to successive equal increments of
angular position, will be in geometrical progression, during
which the work done will be inversely as the intervals of
time in which each portion of it is performed.
If we assume, therefore, that the deteriorating effects of
friction are diminished in both forms of joints by an increase
of the rapidity of movement during a given amount of work,
the advantage which is gained by the organic joint in time
saved is greater than that gained by the artificial joint. For
time is an essential condition in the restoration of organised
matter, deteriorated by functional action. This condition of
time determines that alternation or rhythm which characterises
all the phenomena of organised bodies. The alternate inter-
vals of action and inaction, of fatigue and repose, of deteriora-
tion and renovation, of waking and sleep, of life and death,
are not solely due to the recurrent cosmical conditions under
which organisation subsists, but essentially depend on the
organic character of organised matter itself. Every portion
of organised mechanism is constructed on principles which
co-ordinate it with the peculiar molecular constitution of
organised matter. It therefore appeared to be essential, that
264 CURVATURES AND MOVEMENTS, ETC.
not only the structures and phenomena recorded in this com-
munication should be recognised as in accordance with the
principles of organisation, but also that the generalisation of
these structures and phenomena, as apparently determined
by the law of the equiangular spiral, should be found to
supply the requirements of these principles.
36. The principle involved in the gain of time provided
for repose after functional activity in organic structure is still
further illustrated by an arrangement in organic joints, first
indicated in my former communication on this subject. All
organic joints consist of at least two articular couples, or of
two articular combinations. The two couples or two com-
binations are so arranged that during the full action of the
joints i.e., during the performance of its two opposite move-
ments the one couple or combination performs the work
during the first half of the first movement and the last half
of the second movement, while the other couple or combina-
tion performs the work during the last half of the first move-
ment and the first half of the second movement. The effect of
this arrangement is, that each of the two couples or combina-
tions is alternately in action and out of action. While the
one couple or combination is doing work and undergoing de-
terioration, the other couple or combination is relieved from
functional activity, and engaged in its own necessary repara-
tion that is, in its own nutritive actions.
THE RETINA. 265
XII.ON THE EETINA.
THE anatomical elements of the retina are most satisfactorily
examined in microscopic sections made at right angles to
the surface of the membrane, after maceration in dilute solu-
tion of chromic acid. Viewed in this manner, the retina
exhibits, from the peripheral to the central margin of a suc-
cessful section, a series of strata, which may be distinguished
as the bacillary, white cellular, grey cellular, filamentary, and
limitary layers.
The bacillary layer consists of two kinds of bodies the
rods and cones. The rods are cylindrical or prismatic, with ex-
tremities transversely truncated, transparent, and of extremely
delicate texture. The cones only differ from the rods in
having their inner third, or two-thirds, pyriform. These are
arranged close together at right angles to the outer surface of
the retina, with their external extremities applied against the
inner surface of the choroid. Throughout the greater part of
the retina the rods predominate, the cones being uniformly
interspersed. In the neighbourhood of the yellow spot, the
cones become more frequent; and in the spot itself, they
alone constitute the bacillary layer.
The transversely truncated inner extremity of each of the
rods is connected with the deeper structures of the retina,
either by a conical appendage, which tapers inwards in the
form of a filament, or by an ovoidal appendage, which also
transmits a filament inwards. The inner extremity of each
of the cones is terminated by a pear-shaped appendage,
266 THE RETINA.
containing a nucleus, and having its stalk prolonged inwards,
like the filaments of the rods.
The white cellular layer is composed of three strata an
outer, an intermediate, and an inner. The outer consists of
the ovoidal nucleated appendages of the cones ; of the ovoidal
appendages of the rods which have such bodies attached ; and
of similar bodies in which the conical appendages of the
other rods terminate. The intermediate presents a semifluid
granular basis, through which numerous filaments pass from
the outer into the inner stratum, in a direction perpendicular
to the surfaces of the retina. These filaments, which issue
from the outer stratum, are, firstly, the prolongations of the
filaments which proceed from the nucleated appendages of
the cones ; secondly, the prolongations of the filaments which
proceed from the ovoidal appendages of the rods possessing
such ; and, thirdly, filaments proceeding from the inner extre-
mities of the ovoidal bodies, which are connected with the
filamentary terminations of the conical appendages of the
other rods. The inner stratum also consists of two sets of
ovoidal bodies, each of the first connected with some one of
the prolongations of the filaments of the cones, and giving off,
at its opposite end, a similar filament ; while those of the
second set, similarly formed and provided, are connected with
the prolongations of the filaments of the rods.
Towards the circumference of the retina, many rods may be
found, connected by the filaments proceeding from their ovoidal
bodies with a single filament passing into the inner stratum.
This connection never occurs between the filaments of the
cones, which are thus invariably independent of one another.
There may generally be found a branch passing obliquely
inwards from some part of the filament of the cone and rod,
in its passage through the intermediate stratum, or from the
ovoidal bodies of the inner stratum.
The grey cellular layer consists of a fine granular basis,
THE RETINA. 26*7
such as may be seen in many parts of the brain ; of numerous
cellules, with distinct nuclei, nucleoli, and two, three, or four
radiating and branching prolongations, as in the cerebrospinal
axis ; of numerous blood-vessels ; and of prolongations of the
filaments of the rods and cones, passing inwards to the inner
surface of the retina. It is extremely probable that the
nucleated cellules of this layer are connected by certain of
their prolongations to the filaments of the rods and cones ; the
prolongations of the former being continuous with the branches
of the latter in the white cellular layer. It may also be con-
fidently stated that, by means of others of their prolongations,
the nucleated cellules of this layer are connected with the
ultimate filaments of the optic nerve, which form the next
layer of the retina.
The filamentary layer is composed essentially of the
ultimate filaments of the optic nerve. These filaments, as
soon as they pass off from the spot, enter the retina, lose their
medullary sheath and dark margins, and assume a delicately
transparent grey tint, and somewhat varicose form. They
radiate in gradually diminishing anastomosing bundles all
round ; but, on the outer side of the optic nerve, they sweep
in curves from above, and from below to a line which passes
from the centre of the nerve outwards through the yellow
spot, converging at the same time somewhat towards that
spot. The terminations of the constituent filaments of this
layer are probably all continuous with certain of the radiations
of the nucleated cellules of the grey cellular layer. The
meshes formed by the bundles of this layer afford passage
inwards to the continued prolongations of the filaments of the
rods and cones.
The limitary layer completes the retina on the inner side.
It is an extremely thin, perfectly transparent membrane,
which, although continuous throughout, can only be detached
in minute portions, in connection with the terminal attach-
268 THE RETINA.
ments of the filaments of the rods and cones, which terminate
on its outer surface by expanding into conical brushes, or still
more minute threads, which would almost appear to constitute
the membrane itself.
At the entrance of the optic nerve, the bacillary, white
cellular, and grey cellular layers, are necessarily absent ; the
limitary membrane alone covering the inner surface of the
mass of nervous filaments, which, with the arteries, spreads out
on all sides.
Over the macula lutea the bacillary layer consists of cones
alone, the filaments of which do not reach the limitary layer,
at least at the fovea centralis, but terminate in the white cell-
ular layer. The latter exists, except at the fovea. The grey
cellular layer is distinct throughout ; but towards the centre,
and at the fovea, its granular stratum is deficient, the nu-
cleated cellules being crowded together under the limitary
layer. The filamentary layer is deficient as a lamina, over
the entire macula lutea ; but its constituent filaments may be
detected in the midst of the nucleated cellules of the spot.
The peculiar yellow pigment is diffused through all the
textures, with the exception of the bacillary layer.
The structure of the retina is so delicate, and its investiga-
tion so difficult, that much remains still to be determined
regarding the precise connection of its different elements.
The structure of the bacillary layer having been more parti-
cularly examined by Gottsche and Hannover, and the white
cellular layer by Bowman, Pacini traced the filaments inwards
from the rods and cones into the white cellular layer. The
discovery of the filaments themselves, and their passage
inwards to the limitary layer, is due to Heinrich Mliller, by
whom, along with Kolliker, the general anatomical connec-
tions of the microscopic elements of the retina have been
more particularly traced. According to H. Miiller and
Kolliker, the rods and cones are connected by what may now
THE RETINA. 269
be denominated the Miillerian filaments to the limitary
membrane ; the various bodies which constitute the white
cellular layer being connected with these filaments in the
manner already described. The branch which proceeds from
each of the Miillerian filaments in its course through the
inner stratum of the white cellular layer becomes continuous
with one of the radiations of one of the nucleated cells of the
grey cellular layer ; all the cells of this layer therefore being
connected with all the rods and cones of the retina. The
remaining radiations of the cellules of the grey layer, passing
inwards, form the commencements of the ultimate filaments
of the optic nerve in the filamentary layer of the retina.
In reference to those parts in the structure of the retina
upon which that impression is made, which, when conveyed
to the sensorium, terminates in the perception of light, it may
be stated, that the non-sensibility of the retina at the entrance
of the optic nerve, and its perfect sensibility at the macula
lutea, as well as other considerations, prove that this function
is not performed by the filaments of the nerve.
Kolliker concludes, by exclusion of the other elements,
that the rods and cones, with the Miillerian filaments, are the
structures on which objective light first impresses itself. He
believes the seat of this impression to be in the rods and cones,
and also probably in the inner ends of the Miillerian filaments.
He has examined with great care the chemical and structural
characters of these bodies, and has satisfied himself that they
are nervous structures.
Briicke and Hannover conceive the rods and cones of the
bacillary layer to be structures which reflect the light back
again from the outer surface of the retina against the filament-
ary layer, on which it is thus impressed. Helmholtz, again,
who does not admit the sensibility to light of this layer,
believes the reflected light to act upon the grey cellular
layer.
270 THE RETINA.
Having carefully examined the retina since these obser-
vations and views have been published, I have succeeded in
verifying the majority of the structures and relations described
by Mliller and Kolliker ; but cannot coincide with the latter
in opinion that the rods, cones, and Mlillerian filaments are
nervous structures. They have neither the general aspect
nor the anatomical relations of mere nervous textures. Each
rod or cone, with its Mlillerian filament extending inwards to
the limitary membrane, with the ovoidal bodies developed on
it, would appear referable rather to the class of structures to
which the touch-corpuscles and Pacinian bodies belong.
They are structures developed around the extremities of the
ultimate filaments of the optic nerve, for the purpose of
placing those extremities in the necessary position and cir-
cumstances for being impressed by the rays of light. The
ultimate nerve-filament enters the Miillerian stem of the rod
or cone as it passes through the white cellular layer. This
filament is probably, as has been stated, a radiation from one
of the grey cells, which if they be collectively connected to
all the rods and cones, as well as to the filaments of the optic
nerve, may safely be considered, as Kolliker has pointed out,
to be a retinal ganglion, intermediate between the sentient
points of the retina and the sensorium, as well as between the
corresponding points of its own and of the opposite eye. The
ultimate nerve-filament, as it enters the Miillerian stem
obliquely outwards, probably terminates towards or at the
extremity of the rod or cone, so as to have its transverse
section directed outwards at right angles to the axis of the
rod or cone. Let it now be assumed that a ray of light cannot
impress an ultimate optic filament, except it impinge upon
the free extremity in the axis that is, at right angles to the
transverse section ; and let it also be admitted, with Briicke
and Helmholtz, that it is by light reflected from the bottom
of the eye that vision is affected, then the theory of the retina
THE RETINA. 271
in primary vision becomes more consistent. The divergent
pencil of light which proceeds from any visible point to the
eye, becoming convergent after having entered the refractive
media, passing through the perfectly transparent retina, is
probably brought to a point at the surface of the choroid or
outer part of the bacillary layer of the retina, and is not
entirely absorbed there, but is reflected as a divergent pencil.
In passing towards the point of reflection, the rays of the
pencil cannot impress any part of the retina, because they
cannot impinge on any of its nervous elements in the only
manner in which these can be affected viz., against their free
extremities at a right angle. Certain of the rays, however,
of the reflected pencil viz. those which pass along the axis
of a rod or cone in the bacillary layer will impinge in the
proper direction on the contained nerve, and produce the
luminiferous impression. No confusion, therefore, can result
from the multitude of convergent and divergent rays which
is passing through the chamber of the eye, and through the
retina, for those only are capable of impressing which are
reflected along the axes of the cones and rods. The human
sensorium receives from the retina the impression of a picture,
which is not continuous, but made up of detached points ; as
in the vision of the insect, which only sees an object by as
many points as can transmit rays along the axes of its eye-
tubules.
The bacillary layer of the retina belongs morphologically
to the transparent humours of the eye. The original bulb of
the eye, whether it be a mere process of the brain, or partly a
pulp developed on the tegumentary membrane, forms over its
entire free surface transparent (cuticular) structures. That
portion of the free surface of the pulp which is directed
towards the orifice of the eye-follicle, developes the lens, the
cornea, and the vitreous humour. That portion again, in
contact with the inner surface of the follicle, and which
272 THE RETINA.
becomes choroid, developes the bacillary layer with its rods
and cones. As the lens and vitreous humour increase in size,
the pulp or retina becomes cup-shaped, and intermediate
between the two portions of the transparent structure de-
veloped from its original spheroidal surface.
MODE IN WHICH LIGHT ACTS ON THE RETINA. 273
XIIL ON THE MODE IN WHICH LIGHT ACTS ON
THE ULTIMATE NERVOUS STRUCTURES OF
THE EYE, AND ON THE RELATIONS BETWEEN
SIMPLE AND COMPOUND EYES.*
SINCE the publication, in 1826, of Joh. Miiller's Vergleichende
Physiologie des G-esichtssinnes, physiologists have admitted three
fundamental forms of the organ of vision. 1st, The eye-spot,
organised for the mere perception of light ; 2d, The compound
eye, in which the picture on the nervous surface is a mosaic ;
3d, The simple eye, in which the retinal picture is continu-
ous. The difference between the simple and compound eye,
as explained by Miiller, and since generally admitted, consists
in this, that the formation of the picture in the simple eye is
the result of the convergence of all the pencils diverging from
the visible points of the object on corresponding points of the
retina, by means of the lenticular structures of the organ ;
while, in the compound eye, the picture is formed by the
stopping off, by means of the constituent crystalline columns
of the eye of all rays except those which pass in or near the
axes of the columns. The extent of surface of any object, and
the number of separate parts of such surface, represented on
the nervous structure of a compound eye, will vary, therefore,
in terms of the distance of the object, the curvature of the
superficial ocular surface, the corresponding inclination of the
crystalline columns to one another, the size of their individual
* Read before the Royal Society of Edinburgh, April 6, 1857.
T
274 MODE IN WHICH LIGHT ACTS ON THE RETINA.
transverse sections, and their lengths. The continuous retinal
picture in the simple eye is psychically interpreted as a con-
tinuous image. If, therefore, the possessor of a compound eye
perceives a continuous image of an object, it must be the
result of a more complex psychical operation, in virtue of
which the separate portions of the ocular mosaic picture
are psychically combined, and interpreted as a continuous
whole.
The successive researches of Treviranus, Gottsche, Han-
nover, Pacini, H. Muller, and Kolliker, have determined the
existence and general structure of close-set rods or columns,
which extend between the inner and outer surfaces of the
retina, in the midst of the nervous and vascular textures of
that membrane. The outer extremities of these rods present
a crystalline columnar aspect, and constitute, collectively, the
external layer of the retina, usually termed Jacob's membrane.
The ultimate filaments of the optic nerve, after being connected
in a plexiform arrangement in the ganglionic layer of the
retina, terminate each independently in the more perfect portion
of the retinal field, by passing into, or becoming continuous
with, the inner end or side of a rod. Kolliker considers these
rods as nervous structures that is, as terminal portions of the
nerve-filaments themselves ; and holds that they constitute the
parts of the nervous structure of the eye on which objective
light primarily acts.
Having myself carefully examined the structure to which
I have now alluded, I have been able to verify the more im-
portant anatomical details, as described by their discoverers,
and agree with Kolliker in considering the rods as the primary
optic apparatus. I cannot, however, coincide with this dis-
tinguished observer in holding these rods as modified nerve-
filaments. I hold them to be special structures appended to
the extremities of the ultimate nerve-filaments, and referable
to the same category as the Pacinian bodies, touch-corpuscles,
MODE IN WHICH LIGHT ACTS ON THE RETINA. 275
rods of Corti, etc. ; and, moreover, so far am I from coinciding
with Kolliker in his speculations as to the part of the rod on
which the objective light acts, that I have found myself com-
pelled, not only from the consideration of the structures them-
selves, but also from the development of the eye itself, and
the arrangements of the compound eye, to conceive the rays
of light as acting upon the retina, not as they impinge upon
it, or pass through it from before, but as they pass backward
again out of the eye after reflection from the choroid.
The general aspect of the rods, and more especially of
those portions termed Mlillerian filaments, where they col-
lectively amalgamate in the limitary membrane of the retina,
indicate, as I believe will be generally admitted, that they
consist of a modification of connective tissue, enveloping and
supporting the extremities of the ultimate nerve-filaments in
such a manner as to form special structures, which, from their
functions, may be termed photcesthetic bodies.
That special structures are required for the initiation of
action in the filaments of the optic nerve by objective light,
appears to be established by the facts, that the nervous fila-
ments of the retina, and the cut extremities of these filaments
on the stump of the optic nerve, are not affected by it, although
irritation of the same filaments by electrical or other means
produces subjective luminous phenomena. Subjective sounds
may be produced by various modes of irritation ; but actual
sonant vibrations can only excite the acoustic filaments through
the medium of the rods of Corti, or the corresponding terminal
structures in the vestibule. Corresponding terminal structures
are in like manner appended to the tactile, olfactory, and
gustatory nerves, apparently for a similar purpose, to provide
the necessary conditions of the initial excitement of the nervous
current by those secondary properties of external bodies to
which the organs of touch, taste, and smell, are related.
When the attention of anatomists was directed, a few years
276 MODE IN WHICH LIGHT ACTS ON THE RETINA.
ago, to the structure and physiological signification of the
columns of the retina, by the observations of H. Miiller and
Kolliker, I became satisfied that those structures are not, as the
latter asserted, nervous structures, properly so called, but
special structures, of the same nature as the Pacinian bodies
and the tactile corpuscles. I stated and explained my opinion
of the nature of these bodies in a lecture on the retina delivered
and reported in 1854* But I had generalised these relations
of nervous filaments to special terminal exciting structures,
still further, in the zoological lectures which I delivered in
1853, for my late distinguished colleague and preceptor, Pro-
fessor Jameson. I also expounded it at considerable length
in my course of lectures last winter (1855-6). I shall now
state the doctrine in general terms, not only because it is
necessary for the elucidation of the distinctive characters of
the simple and compound forms of eye ; but also because I
am anxious to put on record, by submitting it to this Society,
a generalisation which appears to me of primary importance
in the general physiology of the nervous system. I assume,
as established the doctrine of Du Bois Eeymond, that a nerve-
filament is capable of propagating the nervous current equally
well in both directions ; and that the physical and physiolo-
gical characters of this current differ in no respect, are in fact
identical in the so-called motor and in the so-called sensory
filaments, whether special or common. I also assume as
established that the specific manner in which a centripetal
nerve-current is converted at the central extremity of the fila-
ment that is to say, is physiologically reflected into the motor
filaments, or psychically interpreted as sensation depends
upon the physiological or psychical endowments of the differ-
ent portions of the nervous centre with which the filaments
are connected. These two positions being assumed, then, I
hold that, although the ultimate nervous filament may have
* Edinburgh Medical Journal, p. 377, 1855 ; and No. XII. in this volume.
MODE IN WHICH LIGHT ACTS ON THE RETINA. 277
its functional current (that is, the common nervous current)
excited or initiated by electrical or other physical or chemical
agencies, yet this current can only be initiated or excited, for
the special functional purposes for which each nervous fila-
ment is provided in the economy, by the structure or tissue
with which such filament is connected peripherally. If so,
then not only are the individual filaments of the nerves of
special sense provided with current-exciting structures at
their peripheral extremities, by means of which alone the
objects to which they are related can initiate the nerve-cur-
rent ; but also centripetal nerve-filaments of whatever kind
are provided, in their connection with the textures from which
they proceed, with arrangements by means of which alone
their functional currents can be initiated.
From this point of view every particular structure in the
organism from which nervous filaments proceed to the nervous
centre may be considered, with reference to the nervous
system, as a peripheral nervous organ that is, an organ
capable of exciting or initiating centripetal nerve-current;
which is physiologically converted, or psychically interpreted,
at the corresponding central organ, according to the special
endowments of that central organ.
After this preliminary statement, I am in a position from
which I can explain the mode in which I understand the
structure and actions of the rods of the retina in the simple,
and the columns in the compound eye.
1. In the Simple Eye. A ray of light can only impress an
ultimate retinal nervous filament under certain conditions.
These conditions are, that it should impinge upon the distal
extremity of the filament in, or parallel to, the axis of that
filament, or within a certain angle to that axis.
All rays impinging on the distal extremity of an ultimate
retinal nervous filament under the conditions stated I term
photogenic rays. Kays impinging upon, or passing through,
278 MODE IN WHICH LIGHT ACTS ON THE RETINA.
the filament in any other direction, may be termed aphotogenic.
The distal portion of the ultimate retinal nervous filament I
distinguish as the photcesthetic surface.
In order that the ultimate retinal nervous filament may
be subjected to the rays of light under the required conditions
of vision, its distal extremity or photaesthetic surface is inclosed
in a peculiar structure, consisting of a so-called rod or cone
(which I distinguish as the crystalline column), and its ap-
pended Mullerian filament, with its nuclear enlargements.
This structure constitutes a specific kind of peripheral nervous
organ, which, from its function, I term a photcesthetic body.
A photsesthetic body consists of a distal segment, or
dioptric portion, elongated, cylindrical, or club-shaped, homo-
geneous, transparent, and highly refractive, usually termed
the rod or cone ; and a proximal segment or peduncle, with
its nuclear enlargements, into which the ultimate nervous
filament passes, and within which it apparently terminates,
probably at its outer end.
The entire aspect and arrangement of these photaesthetic
bodies, their predominance over the other parts of the retina
at the axial spot of the eye, and the direct continuity of their
stems with the nerve-filaments at that spot, appear to me to
indicate not only the nature of their functions, but also the
general features of the mode in which it is effected. It
appears to me that the rays which act upon the nervous
filaments must be such rays as the arrangement permits to
pass from behind forwards in the axes of the photaesthetic
bodies. It has now been ascertained, that the quantity of
light reflected, and consequently irregularly dispersed within
the eyeball from the choroid and bacillary layer, etc., is very
considerable ; and it consequently becomes a very important
question, to determine in what manner this reflected and
irregularly-dispersed light is prevented from affecting the
retina. The view which I have already given of the structure
MODE IN WHICH LIGHT ACTS ON THE RETINA. 2*79
and probable mode of action of the photsesthetic bodies affords
the basis of a hypothesis which meets all the conditions of
the question, and is in full accordance with the comparative
anatomy and development of the organ of vision. I cannot
interpret the functions of the structure of the retina as now
determined, except by assuming that the photsesthetic columns
are impressed not by the light as it enters the eye, or as it is
more or less irregularly reflected and dispersed in its interior,
but only by those rays which, in their passage backwards to
the pupil, pass along, or nearly in, the axes of the crystalline
rods or columns of the photeesthetic bodies, so as to reach the
photaesthetic spots under the required conditions. No con-
fusion, therefore, can result from the multitude of convergent
and divergent rays which pass through the chamber of the
eye, and through the retina. By this means, the numerous
rays not necessary for vision, are as it were eliminated from
the operation, the eye being blind to them, and affected only
by such as are reflected backwards to the pupil along the axes
of the crystalline columns.
2. The Crystalline Columns of the Compound Eye. As
stated in my lecture on the retina, formerly alluded to, I
conceive the crystalline columns in the eye of the insect or
crab to act in the same manner as the retinal rods in the
spheroidal or simple eye. That they do so may be held as
established by the researches of J. Miiller on the laws of
vision in the compound eye. Miiller even refers to the
columnar structure of the retina, as presenting a certain
similarity to the structure or arrangement of the compound
eye. F. Leydig, in an elaborate memoir published in Miiller's
Archiv. in 1855, on the structure generally of the Arthropoda,
examines minutely the structure of the simple and compound
eyes, and arrives at the conclusion that the crystalline columns
of their compound eyes, as well as the corresponding structures
in their so-called simple eyes or ocelli, are of the same nature
280 MODE IN WHICH LIGHT ACTS ON THE RETINA.
as the so-called rods and cones that is, the photsesthetic bodies
which I have already described in the retina of the vertebrate
eye. But Leydig entirely loses sight of a fact, which, if un-
explained, vitiates his conclusion as to the physiological
identity of the bodies in question. In the ammlose or
molluscous eye, whether in its so-called simple or compound
form, the crystalline columns are directed, like the tubes of
so many telescopes, towards the object, the corresponding
nervous filaments passing to them from behind ; whereas the
crystalline rods of the vertebrate retina are directed away from
the object that is, towards the back of the eye are in contact,
in fact, with the choroid, while their nervous filaments are con-
nected to them in front that is, between them and the object.
On the other hand, if I am correct in holding that the
vertebrate eye is acted upon by those rays only which are
reflected from its choroidal surface, I have not only explained
physiologically why its retinal columns are reversed, but I am
legitimately entitled, as Leydig is not, to consider them as the
homologues of the crystalline columns of the annulose and
molluscous eye.
But the teleological explanation of the opposite arrange-
ment of the corresponding structures in the vertebrate and
invertebrate eye, is, in the present phase of the science, in-
sufficient. The difference must be explained morphologically.
This explanation is afforded by the different modes in which
the vertebrate and invertebrate that is, the simple and
compound eyes are developed.
In the compound eye the primordial ocular papilla or
convexity, which is only slightly protuberant, has its
cutaneous or superficial surface immediately converted into
the crystalline columnar structure, the individual columns of
which are connected with the filaments of the subjacent optic
nerve. The columns are all therefore directed to the object.
The primordial cerebro-cutaneous spheroidal protuberance
MODE IN WHICH LIGHT ACTS ON THE RETINA. 281
or papilla of the simple refracting or vertebrate eye, is speedily
hollowed out in front by the development in or upon it of the
lens and vitreous humour, so that from a spheroidal convex
surface, the primordial protuberance assumes the form of a
cup, with its mouth directed forwards, and its cavity occupied
by the refracting media of the organ. This cup-shaped mass
is the retina ; the crystalline rods are not developed on its
concave surface, but on its outer or convex surface, as they
exist on the convexity of the compound eye that is, in the
direction of the radii of the sphere, but directed backwards,
on account of the nearly spheroidal surface.
In conclusion, I may state what appears to be the
physiological superiority of the simple over the compound
eye. As the simple eye is acted on by reflected light only,
it cannot be disturbed by rays not required for the definition
of the image. It is also arranged so as to admit of a much
more delicate or minute mosaic representation of the object,
from its microscopic and reversed photsesthetic bodies being
in contact with the reflecting choroidal surface on which that
image is formed. It moreover combines the advantages of
the contiguous image, formed by the lenticular structures, and
the mosaic image, which results from its crystalline rods.
282 LAMINA SPIRALIS OF THE COCHLEA.
XIV. ON THE LAMINA SPIEALIS OF THE
COCHLEA.
THE lamina spiralis of the cochlea, instead of being, as hitherto
supposed, a single layer, osseous in the inner, and membran-
ous in the outer portion of its extent, is a double structure,
with numerous complex arrangements in its interior.
The osseous and membranous portions of the lamina
spiralis, as hitherto understood, may be considered as the
basis of the entire complex structure as it is now ascertained.
The osseous portion of the lamina contains the cochlear
nerves in closely-arranged canals, which, at its outer margin,
coalesce in a chink or fissure, which contains the ganglion
recently discovered by Corti, and affords exit to the nervous
filaments.
The membranous portion of the lamina consists, as
discovered by Todd and Bowman, of a membrane which,
except at its outer and inner margins, is closely streaked in
the direction of the radius of the cochlea, and hence denomi-
nated zona pectinata. The outer margin of the membrane is
attached by means of a fibre-nucleated texture to the accessory
spiral lamina of Huschke, and to the neighbouring groove.
This fibro-nucleated structure is the cochlear muscle of Todd
and Bowman the spiral cochlear ligament of Kolliker. The
inner margin of the membrane is attached to that lip of the
fissure of the osseous lamina which is next the apex of the
cochlea, but so as to leave numerous orifices or more or less
oblique canals, through which, as Kolliker has ascertained,
LAMINA SPIRALIS OF THE COCHLEA. 283
the extremities of the cochlear nerve-filaments pass to the
vestibular surface of the membrane. The cochlear nerves,
therefore, instead of being distributed, as has hitherto been
supposed, on the tympanic aspect of the lamina spiralis, pass
through it to its vestibular aspect ; its entire tympanic sur-
face, and the nerves in their transit across that surface, from
the fissure in the osseous to the orifices in the membranous
portion, being covered by the fibro-serous lining membrane of
the osseous labyrinth. It thus appears that all the complex
structures in connection with the lamina spiralis, usually so
called, of the cochlea, are situated on its vestibular aspect.
These structures are 1. The habenula sulcata, situated
chiefly on the osseous lamina, and discovered by Todd and
Bowman ; 2. The habenula denticulata, situated on the mem-
branous lamina, discovered by Corti, and latterly ascertained
by Kolliker to be connected with the cochlear nerves ; 3.
The membrane of Corti, covered on its vestibular surface by
the serous lining membrane of the osseous labyrinth, first
partially recognised by Corti, but latterly more fully described
by Claudius ; 4. Large vesicular cells which occupy the
space between the membrane of Corti and the lamina spiralis,
usually so called, first recognised by Corti, but more precisely
determined by Claudius.
The habenula sulcata is a structure of cartilaginous aspect,
which, rapidly increasing in thickness as it advances to the
outer margin of the osseous lamina, inclines over and beyond
that margin so as to form the sulcus spiralis of Huschke. It
consists of columns, which at its thin inner edge are set per-
pendicular to the surface of the subjacent bones, and therefore
expose their free extremities on its vestibular aspect. To-
wards its thick or outer edge the columns become more and
more inclined, so as to expose more and more of their sides,
and at the edge itself they form a series of elongated, slightly
clavate and flattened, clear glistening teeth, which project
284 LAMINA SPIRALIS OF THE COCHLEA.
over the groove of Huschke. Some of the columns divide,
others unite together, as they pass outwards to form these
teeth ; which are termed " teeth of the first series." In the
grooves between the columns are numerous nuclei, which
resist acetic acid, while the former swell up, and become
somewhat striated under its action.
The habenula denticulata consists of a series of apparently
jointed rods, laid on the surface of the membranous portion
of the so-called lamina spiralis ; each rod in the series lying
in the direction of the radius of the cochlea. The first or
inner segments of these rods form a series of compressed
laminae, attached across the bottom of Huschke's spiral
groove, with narrow chinks between them, which are, in fact,
the orifices through which the cochlear nerve-filaments pass,
as already stated. These central segments are the "dents
apparents " of Corti. The second segment, or portion of each
rod, is also compressed, and lies flat on the membranous
spiral lamina, and is loose and movable, except at its inner
end, where it presents an enlargement like a nucleus, which
was supposed by Corti to be the joint by means of which the
rod is attached to and moves on the membrane ; but which
Kolliker has discovered to be the point at which one or more
of the ultimate filaments of the cochlear nerves become
connected with the rod, after they have passed through the
orifices already mentioned. The series formed by these
second segments of the rods are the so-called " teeth of the
second order." The terminal segment is connected with the
second by means of two short quadrilateral segments, the
" coins articulaires " of Corti. The terminal segment is elon-
gated and compressed. To its upper surface three pyriform
bodies, each of which contains a nucleus, are attached by
short peduncles, so as to be laid over one another, from
within outwards. Corti and Kolliker describe the outer
extremity of this segment as somewhat expanded and forked,
LAMINA SPIRALIS OF THE COCHLEA. 285
and also as free or loose. But Claudius has ascertained that
the expanded extremity is attached to the lamina pectinata,
so that the rod cannot move to and from the membrane, as
Corti has supposed.
It must here be observed, that the first or inner segments
of the rods, the " dents apparents " are attached throughout,
and from their position and relations belong rather to the
structure of the habenula sulcata, than to that of the habenula
denticulata. The latter consists, then, essentially of the
second and terminal segment described above, connected
together by the short " articular " portions. The cochlear rod,
properly so-called, consists therefore of two principal segments,
the inner segment being connected with one or more ultimate
nerve-filaments, and the outer fastened at its external end to
the membrane on which it lies.
Corti has described a thin membrane covered by the
epithelium of the labyrinth, and extending from the pro-
minent surface of the habenula sulcata somewhat beyond the
habenula denticulata. The space between this membrane
and the "dents apparents," and also the spiral groove of
Huschke, are occupied, according to him, by large transparent
nucleated vesicles. Similar vesicles, conceived to be epithelial
by their discoverer, occupy the space between the mem-
branous lamina spiralis and that portion of Corti's membrane
which extends beyond the habenula denticulata. The rods of
the cochlea, therefore, according to Corti, move like a series
of hammer or pianoforte keys, in a space included between
the membrane discovered by him, and the lamina spiralis,
usually so-called. Claudius, however, has shown that Corti's
membrane extends out to the external wall of the cochlea ;
and that the entire space between it and the lamina spiralis,
usually so-called, is occupied by vesicular structure.
The following are the results of observations made for
the purpose of verifying the descriptions of Corti, Kolliker,
286 LAMINA SPIRALIS OF THE COCHLEA.
and Claudius. The membrane of Corti extends, as Claudius
has stated, to the outer wall of the cochlea, and the large
cells between it and the lamina spiralis have extremely
thin walls, and transparent contents, so that they resemble,
when pressed together, an areolar network. Portions of
the rods were also occasionally seen curled up, and as ob-
served by Claudius, attached by their expanded extremi-
ties, in series, to the membrane on which they lie. The
detection by Kolliker of the connection of the nerve-fila-
ments with the rods is, after the discoveries of Corti, the
most important recent addition to our knowledge of the
structure of the cochlea. Even in the ordinary view of the
structure from the vestibular aspect, the nerve-filaments may,
without much difficulty, be observed to disappear at or in the
central extremities of the rods. Their inner extremities do not
correspond, as Kolliker has correctly observed, to the outer
ends of the " dents apparents," but to the intervals between
the latter. Kolliker holds, on chemical as well as anatomical
grounds, that the rods of Corti are true terminations of the
cochlear nerves peculiar forms of the ultimate nerve-fibre.
He believes Corti's opinion to be erroneous, that they are
developments from the membrane on which they lie, and that
they constitute a physical apparatus. Notwithstanding K61-
liker's opinion, it may be safely asserted that the rods of Corti
present a configuration and aspect which distinguish them in
the most marked manner from any form of the nerve-filament.
The peculiar flattened articulated form, the variable breadth,
and, as pointed out by Claudius, the alternate arrangement of
the proximal and distal segments of neighbouring rods ; and,
lastly, the elasticity, slight, though marked, which they possess,
indicate that they are not true nerve-structures. Without
stating the nature of the function he supposes them to per-
form, Corti believes that the rods move like a series of ham-
mers. Harless conceives that they act as dampers by pressing
LAMINA SPIRALIS OF THE COCHLEA. 287
on the membrane during vibration. Kolliker, again, believes
that from the almost mathematical regularity with which they
are arranged along the vestibular surface of the lamina spiralis,
these peculiar terminations of the cochlear nerves are the
structures which distinguish the pitch, timbre, and strength
of sounds, through the medium of the water of the labyrinth
and the fenestra ovalis.
From comparative anatomy it would appear that the
vestibule is that part of the organ by means of which any
sound, or series or combination of sounds, is heard merely as
noise. The simplest form of ear, which consists of a vesti-
bule only, probably enables the sensorium merely to become
cognisant of sound, irrespective of the pitch or harmony of its
constituent tones.
In regard to the semi-circular canals, it appears probable
from their intimate connection with the vestibule, that they,
like it, have to do with sound merely as noise, and that their
function, therefore, is of secondary importance in the higher
forms of the organ.
Dr. Thomas Young, with his usual sagacity, considered
the cochlea as a " micrometer of sound." Kolliker, as already
stated, has put forward a similar idea, based on his know-
ledge of the structures just described. His conception, how-
ever, appears to be so far unsatisfactory, inasmuch as he
considers the rods of Corti to be merely the extremities of the
cochlear nerves ; and it wants that completeness which it
would have, had he been able to admit those rods to be a
series of acoustic arrangements, as they are believed to be by
their discoverer.
The hypothesis presents a more satisfactory form if we
assume that each of the rods of Corti, or that groups of these
rods are so organised and arranged as to act or vibrate as
acoustic apparatuses appended to the extremities of the coch-
lear nerves. Each rod, or group of rods, may be so constituted
288 LAMINA SPIRALIS OF THE COCHLEA.
as alone, among all the others, to act or vibrate, when the
note or harmonic chord, for which that single rod, or that
group of rods, had been provided, passes through the cochlea
in the form of sonant vibrations of a correspondent physical
value. If this be the case, we can understand how, by the
instrumentality of a cochlea, the physical value of each tone,
or harmonic combination of tones, may be detected by the ear,
and impressions of correspondent value transmitted along the
nerve-filaments to the seat of sonant sensation in the brain.
It must be borne in mind, however, that the sesthetic percep-
tion of the sensations produced by the instrumentality of the
cochlea, its nerves, and the sentient centre, is a psychical
function, and a result of the pre-established harmony between
the mental and corporeal elements of the animal constitution
on the one hand, and external nature on the other.
ELECTRICAL ORGANS IN FISHES. 289
XV. ON THE ELECTEICAL APPAEATUS IN TOE-
PEDO, GYMNOTUS, MALAPTEEUEUS, AND EAIA.
THE electrical apparatus in fish consists of three parts the
battery, the nervous centre, and the internuncial cord.
The following would appear to be the general expression
for the structure of the battery a very large number of
laminse, consisting of vascular nucleated texture, largely sup-
plied with centrifugal nerve-fibres, distributed on one of their
surfaces only ; so arranged in reference to one another, and to
thin intervening layers of fluid, as to constitute a uniform
series, in the order : nerve-surface cellulo-vascular surface
fluid, nerve-surface cellulo-vascular surface fluid, etc. etc.
The nervous centre consists of a portion of the cerebro-
spinal axis developed in relation to the large nerves distributed
to the battery ; and so organised, as to be capable, not only
of excito-motory action, but also of being subjected to the
influence of the will
The internuncial cord is a centrifugal nerve, connected at
one extremity to the nervous centre of the apparatus, and at
the other distributed on the nervous surfaces of the lamina
of the battery.
In Torpedo there are two batteries which occupy the two
spaces between the pectoral fins, the head, and gills. Each
battery consists of a number of hexagonal, pentagonal, or
tetragonal prisms, which vary in number from 400 to up-
wards of 1000, according to the age of the animal. The prisms
extend perpendicularly between the dorsal and abdominal in-
tegument ; and are separated from and connected to it by a
u
290 ELECTRICAL ORGANS IN FISHES.
thin but dense aponeurosis, which at the same time separates
them all from, and connects them to one another, by passing
inwards in single layers, so as to form a continuous series of
prismatic aponeurotic compartments, in the interior of which
the prisms are situated. Each prism consists of delicate,
horizontal, superimposed laminae, separated from one another
by thin layers of fluid, so that the arrangement bears a general
resemblance to a galvanic pile. It has hitherto been supposed
that the laminae are connected by their margins to the
aponeurotic wall which surrounds the prism ; but Pacini
(Sulla struttura intima dell organo elettrico del Gimnoto, e di
altri pesci elettrici, 1852) has lately shown that the laminae
are attached by their angles only to the comers of their apo-
neurotic sheaths ; and that an entire pile may be removed from
its containing cavity, by cutting the four, five, or six series of
attachments by which it is fixed. It is extremely important
that the structure of the laminae should be determined.
Valentin ("Electricitat der Thiere," mW&gnQT'sffandwdrterluch
der Physiologie) states, that each lamina consists of a thin
prolongation of the aponeurotic wall of the pile, covered above
and below by an epithelial layer, and affording a matrix for
the ultimate divisions of the vessels and nerves, which, he is
inclined to believe, are so arranged, that the terminal nervous
plexuses are placed towards the upper, the capillaries towards
the lower surface. Savi (Matteucci and Savi, Traitt des
Phenom&nes Electro-Physiologiques, 1844) describes the ele-
mentary filaments of the nerves as forming a network by
anastomosis in the lamina ; but Eudolph Wagner (Annales
des Sciences Naturelles, 1847) has shown that each elementary
filament, enveloped in a very thick sheath, divides at once
into twelve to twenty-five secondary filaments, which, passing
towards the laminae, splitting into two or three ternary fila-
ments and losing their envelopes and dark contours, disappear
in the soft, dotted, nucleated substance of the laminae, without
ELECTRICAL ORGANS IN FISHES. 291
forming meshes. Pacini (loc. cit.) has lately made a most
important addition to Wagner's description of the laminae.
The laminse, or electrical diaphragms, as Pacini terms them,
are attached, as has been already stated, by their angles only.
The vessels and nerves enter at these points, but so as to be
at first placed on the under surface of the diaphragm, and there-
fore in the fluid interposed between that surface and the upper
surface of the diaphragm below. Passing inwards and ramify-
ing in this fluid, they ultimately pass up to the under surface,
and the nerves are distributed on that surface only of the dia-
phragm to which they belong. Now, as the dorsal surface in
Torpedo is positive and the abdominal surface negative, it
follows, as Pacini has indicated that the upper surface of each
electrical diaphragm, consisting only of soft, dotted, nucleated
vascular texture, is positive, while the under surface, on which
the nerves only ramify, is negative.
Pacini was led to the observation of the position of the
nerves in the electrical diaphragms of Torpedo, by the more
complex structure which he had previously discovered in the
corresponding parts of Gymnotus.
Gymnotus possesses four batteries, which extend nearly
the whole length of its eel-like body, from behind the pectoral
fins to the extremity of the tail ; forcing the lateral muscles
towards the dorsal, and the comparatively small abdominal
viscera, with the anus, towards the cephalic region. The great
or dorsal batteries are separated from one another above by
the vertebral column, the great vessels, the displaced lateral
muscles, and the air-bladder ; below by a mesial aponeurotic
septum, along which the nerves pass to the batteries and
ventral fin. Laterally these dorsal batteries are intimately
connected to the skin ; and inferiorly are separated from the
ventral, or small batteries, by a thin layer of muscle. The
small batteries are, moreover, separated from the skin by the
laterally-displaced muscles of the ventral fin ; but are inti-
292 ELECTRICAL ORGANS IN FISHES.
mately connected to one another by a thin aponeurosis only.
These small batteries are, therefore, peculiar, not only in their
close approximation, but also in being enveloped in mus-
cular substance.
The batteries in Gymnotus consist of a number of piles
placed horizontally in a direction from head to tail. From
this circumstance, as well as from their peculiar structure, they
are aptly compared by Eudolphi to galvanic troughs. These
troughs are in the form of flattened masses, separated from,
but connected to one another by aponeurotic septa, which,
diverging, extend outwards from the inner to the outer aspect
of each battery. It is not easy to determine the exact number
of the piles or troughs in a battery, as they vary in number
in different parts of it, and are lost as they pass backwards
and downwards. From the statements of Mr. Hunter (An
Account of the Gymnotus Mectricus ; Phil. Trans. 1775),
and Valentin (loc. cit.\ and my own observations, the number
of troughs in the great battery ranges from thirty to sixty ;
in the lesser from eight to fourteen. Hunter (loc. cit!), Eu-
dolphi (uber die Mectrischen Fiscke in Alhand. der Akad.
zu Berlin, 1822), Knox (Edin. Jour, of Science, 1824), Valentin
(loc. cit), and all observers previous to Pacini, state what may
be easily verified, that the troughs in Gymnotus consist of
numerous perpendicular laminae, which extend transversely
between the aponeurotic septa, with fluid interposed, as in the
piles of Torpedo. Pacini's account (loc. cit.) of the structure
and relations of the electrical laminse or diaphragms of
Gymnotus is much more precise ; and elucidates in a remark-
able manner a structure hitherto sufficiently obscure. The
more important features of Pacini's account, as verified by
myself, may be thus described. Each of the electric dia-
phragms in Gymnotus, instead of being, as in Torpedo, a
single lamina with the nerves distributed on one of its surfaces,
consists of two lamina^ with a thin layer of fluid interposed.
ELECTRICAL ORGANS IN FISHES. 293
The posterior of these is a delicate, wide-meshed, fibrous layer,
in which alone the nerves ramify ; the anterior consists of
a thicker layer of the peculiar vascular, dotted, nucleated
texture which forms the laminae in Torpedo. Both surfaces
of the vasculo-cellular layer present an arrangement of pro-
minent, close-set, undulating ridges, with thick, rounded,
nucleated margins. The ridges are more fully developed on
the anterior than on the posterior surface of the layer, and
from the ridges of the latter a number of thread-like pro-
longations pass backwards through the interposed fluid to the
fibro-nervous layer, so as to connect the two layers as one
compound lamina. From the measurements and calculations
of Pacini, the superficial extent of the anterior surface of the
vasculo-nucleated layer is increased by this rigid structure
from five to six times, the posterior about twice.
The electro-motor series, therefore, in Gyrnnotus, instead
of simple laminae, as in Torpedo, consist of compound laminae
separated by layers of fluid. There are thus two kinds of
fluid in the electro-motor series of Gymnotus firstly, that
between the vasculo-cellular layers and the fibro-nervous,
and which must be considered as an element of each com-
pound electric diaphragm ; and, secondly, that between any
two electric diaphragms, which is the homologue of the fluid
layer in Torpedo.
As the current in Gymnotus passes from before backwards,
Pacini denominates the vasculo-cellular layer the positive, and
the fibro-nervous layer the negative element, of the electro-
motor series.
The batteries in Malapterurus are two in number, sepa-
rated, but at the same time intimately connected to one another
in the mesial plane, along the dorsal and ventral margins of
the body, so as to form a continuous layer of a gelatinous
consistence, closely adherent to the skin, and enclosing as in a
sac the entire animal, except the head and fins. In the
294 ELECTRICAL ORGANS IN FISHES.
Maiapterums of the Nile, of which species only dissections
have hitherto been published (St. Hilaire, Annales de Museum,
torn. i. ; Eudolphi, Abhand. Berl. Akad. 1824 ; Valenciennes,
An. des Sci. Nat. torn, xvi.), a subjacent areolar, laminated,
fatty layer, has been described as a second and deeper electrical
apparatus ; and in the Malapterurus of Western Africa, with
the examination of which I am at present engaged, this
deeper layer exists in the form of longitudinal streaks of
fat between the muscles and gelatinous layer. Pacini, how-
ever (" Sopra 1'organo elettrico del siluro elettrico del Nilo,
etc.," negli Annali delle Sci. Nat. di Bologna, 1846), has shown
that this presumed deep electrical structure consists princi-
pally of fat (as it assuredly does in the species from Western
Africa), and probably acts as an insulator to protect the fish
from its own shocks ; the electrical currents being presumed
to pass from within outwards that is, through any point on
the surface of the body.
The determination of the intimate structure of the battery
of Malapterurus is extremely difficult. Before Pacini, no
precise description of it had been attempted. He represents
the structure as consisting of octahedral cellules or alveoli, a
form which in some measure explains the variable direction
of the currents through the electro-motor mass. Professor
Ecker, in a communication contained in Siebold and Kolliker's
Zeitschrift fur Wissensch. Zoologie, July 1854, states that
Dr. Bilharz,* at present in Egypt, is engaged in the anatomy
of the Nilotic species, and that he conceives he has determined
the alveoli of the electro-motor layer to be lenticular in form,
with their surfaces directed forwards and backwards. He
would appear to have observed that they are arranged not
in antero-posterior series, but alternately ; so as to constitute
* The observations of Dr. Bilharz, the Professor of Anatomy in Cairo, have
since been published in extenso, in a volume entitled, Das Elcdrische organ des
Zitterwelses ; Leipzig, 1857. EDS.
ELECTRICAL ORGANS IN FISHES. 295
decussating series, and to afford in certain sections the
octahedral form attributed to them by Pacini. He also states
that these lenticular alveoli consist of a fibrous membrane,
covered by a very fine layer on which the nerves are dis-
posed.
On each side of the tail of the skate (Eaia), partly in con-
tact with the skin, but chiefly enveloped in the so-called
sacro-lumbalis muscle, is an elongated fusiform mass, which,
although its electro-motor power has not yet been experi-
mentally determined, nevertheless exhibits all the structural
characteristics of an electrical battery. The mass consists of
a number of longitudinally and somewhat spirally arranged
series of discs ; the series being separated from, and connected
to, one another by thicker, the discs by thinner, layers of
areolar texture. The discs are somewhat triangular, quad-
rangular, or pentangular in form, and are invariably arranged,
so that their two large surfaces or faces are directed, the one
backwards, the other forwards ; and their three, four, or five
smaller surfaces or margins enter into the formation of the
surface of the series to which they belong. Of the two large
surfaces, the anterior, or that towards the head of the animal,
is smooth and slightly convex ; the posterior slightly concave,
and presents numerous alveolar depressions of various but
graduated sizes, which penetrate two-thirds through the disc,
and are separated from one another by corresponding straight
or slightly-curved partitions, which diminish in size as they
pass off from three or four primary ridges, which radiate from
near the centre of the surface, and thus separate the alveoli
into larger and smaller elliptical or angular groups. The
discs consist of jelly-like dotted or granular nucleated sub-
stance ; the granules being arranged in the form of spheroidal
shells around clear spaces, in each of which a nucleus is situ-
ated. The ultimate ramifications of the vessels and nerves
are situated not in but on the two large surfaces or faces of
296 ELECTRICAL ORGANS IN FISHES.
the discs ; the former on the concave, alveolar, or posterior
face ; the latter on the convex, smooth, anterior face : and, like
the vascular and nervous trunks and branches of the organ,
lie in the midst of the areolar texture, which forms the
greater and lesser laminae of separation and connection of the
constituent series and discs of the battery. The ultimate
arterial twigs enter the areolar texture which lines the con-
cave face of each disc ; and pass into the alveoli as bundles
of looped capillaries, which are continued into similarly
arranged venous radicles. A number of ultimate nervous fila-
ments spread from one of its margins through the areolar
lamina, which clothes the convex face of each disc, preserving
their double contours, until, becoming somewhat narrower,
they divide into two or three secondary filaments, which,
assuming an elongated fusiform aspect, and enclosing a
nuclear mass, pass into corresponding secondary divisions of
neighbouring filaments. The smooth convex surface of each
disc is thus covered by an areolar lamina, which contains a
network of ultimate branching and anastomosing nerve-fila-
ments ; the secondary or division filaments, which form the
boundaries of the meshes of the network, having a peculiar
festooned or looped fusiform aspect, with a mass resembling
a nucleus in the centre of each.
This organ bears a resemblance to the batteries of Torpedo,
and more particularly to those of Gymnotus, in the peculiar
relations of the nerves, vessels, and nucleated texture ; and if
an electrical current exists in certain circumstances (pro-
bably when the animals are in season), it must pass in a
contrary direction to that of the Gymnotus that is, from
tail to head.
These organs in the tail of the rays were discovered by
Dr. Stark of Edinburgh ; and their relative and general struc-
ture, as well as their probable function, described in an able
paper read to the Eoyal Society of Edinburgh in 1844 (Pro-
ELECTEICAL ORGANS IN FISHES. 297
js of the Royal Soc. Edin. Dec. 1844). As Dr. Stork's
description did not involve a sufficient account of the micro-
scopic structure, which, in the absence of direct experimental
evidence, could alone afford the basis of a legitimate hypo-
thesis as to the function of the organ, I at the time under-
took that inquiry, and stated the results in a paper read at a
subsequent meeting of the Society.* In this paper the pre-
sumed electrical organ was described as consisting of antero-
posterior, or linearly-arranged series of compressed chambers,
lined by a nucleated gelatinous vascular substance ; and sus-
pended in the cavities of the chambers numerous sling-like
anastomosing ultimate doubk contour nerve-tubes, with the
centre of each loop occupied by a nucleus. There was
also described a peculiar undulating ridge-structure (the
alveoli of Eobin), somewhat similar to the grooved and pitted
marking on the dermal plates of certain fossil fishes ; but the
relations of this structure to the nucleated gelatinous texture
were not determined ; although its probable importance was
indicated as a characteristic feature in an organ which could
only be referred to electrical structures.
The entire structure of the presumed electrical apparatus
in the rays, has, since Dr. Stark's discovery, been redis-
covered, and most minutely and accurately described by
Eobin (An. des Sci. Nat. 1847) ; and from his descriptions,
as verified by myself, the account in this lecture has been
derived.
As the four nerves distributed to each battery of Torpedo
are branches of the fifth and eighth cerebral pairs, the nervous
centre of its electrical apparatus is situated in the medulla
* This paper was read before the Royal Society of Edinburgh, 6th January
1845 ; but its title only is recorded in the Proceedings of that day. In a
manuscript found amongst his papers, he states that he was then engaged in
observations on the structure of the electrical organs of two of the electrical
fishes (torpedo and gymnotus), made during dissections for the University
collection. EDS.
298 ELECTKICAL ORGANS IN FISHES.
oblougata, and consists of a large lobe on each side of its an-
terior part. Valentin (" Electricitat der Thiere," in Wagner's
ffandworterb.) states that these lobes consist of nucleated
cellules so large as to be visible to the naked eye. The an-
terior or trigeminal electrical nerve is derived from the non-
ganglionic portion of the third division of the fifth ; the three
posterior or vagal electrical nerves pass out along with the
branchial divisions of the eighth nerve, but have no connec-
tion with the ganglionic masses developed on the branchial
nerves. These electrical nerves belong, therefore, to the non-
ganglionic series, with central relations similar to those of
motor nerves.
The batteries of Gymnotus are supplied by about 224 pairs
of nerves (J. Hunter, Phil. Trans. 1775 ; Kudolphi, Abhand.
der K. Akad. zu Berlin, 1820) on each side. These are all
derived from the inferior or motor roots of the spinal nerves ;
none being supplied by the lateral nerve, or combined branch
of the fifth and eighth. The spinal cord exhibits no peculiar
development, nor indication of the existence in it of a series
of electrical nervous centres ; but Valentin (Wagner's Ifand-
worterb. loc-cit. 1842) has described a great lobe springing
from each side of the brain between the peduncle of the
cerebellum and the mesocephalon, extending upwards and
forwards with its fellow of the opposite side, like an anterior
or supplementary cerebellum. These lobes, according to
Valentin, exhibit no trace of the large characteristic nucleated
cells which exist in the electrical lobes of Torpedo. Whether
the electrical lobes in Gymnotus be peculiar developments of
the cerebellum, or of the grey matter at the cerebral ex-
tremities of the motor columns of the spinal cord, they present
a highly interesting arrangement.
The presumed deep electrical layer of Malapterurus, which
is merely a fatty mass, is supplied by branches of the spinal
nerves ; but the true electrical organs or batteries are supplied,
ELECTRICAL ORGANS IN FISHES. 299
the one on each side, by a longitudinal nerve, accompanied by
an artery and vein, which pass along on their mesial aspects.
This nerve was formerly considered to be a branch of the
eighth pair ; but Pacini (sopra Vorgano dettrico del Siluro
dettrico del Nilo, 1846) describes it as derived from the first
spinal nerve. Ecker has more recently stated (Siebold and
Kolliker's Zeitsclirift, July 1854), that, according to Bilharz,
" the electrical nerve on each side appears to be a new ele-
ment intercalated between the third and fourth spinal nerves."
From, the same communication it appears that Bilharz has
found the trunk of the electrical nerve of the Nilotic Malap-
terurus to consist not of a bundle of ultimate filaments, but
of one such filament only, one-fourth of a line in diameter,
surrounded by three fibrous sheaths, so as to present an entire
thickness of one line. From this remarkable structure, Ecker
has suggested to Bilharz further observations to determine
whether the nervous centre of the electrical apparatus in this
fish may not be a colossal unipolar nerve cell. From the
peculiar structure of the trunk of the nerve, it is also evident
that its branches and twigs of distribution must be subdivi-
sions of the original single filament ; in this respect resembling
the subdivisions of the ultimate filaments in Torpedo, as
observed by Wagner.
The presumed electrical organs in the tail of the skate are
supplied by numerous nervous twigs, derived from the ventral
or motor roots of the spinal nerves of the corresponding portion
of the tail. These are distributed, as already stated, on the
anterior faces of the discs, and do not exhibit at their spinal
extremities any appreciable central development.
Physiologists admit, as a general fact, the disturbance of
the electric equilibrium, in the processes of the living organised
body. In vegetables this development of electricity is re-
markable. In animals the discovery of Galvani, and the
researches of Matteucci, and more particularly of Du Bois
300 ELECTKICAL ORGANS IN FISHES.
Keymond on the electro-motor phenomena of muscle and
nerve, prove that in these structures currents take place, the
result of nutritive process as well as of functional action ;
and the observations of Mr. Baxter (Phil. Trans. 1848-52,
Proceedings of Royal Soc. 1855) have determined the existence
of electrical currents manifested during secretion and respi-
ration. There can be no doubt whatever, that in every living
organism more or less numerous and powerful electric dis-
turbances are produced by its organic processes ; and that its
general electric equilibrium is provided for by the resulting
currents in the organism itself, and in the medium in which
it lives. The problem which the physiologist has to solve, in
attempting to explain the mode of action of the electrical
apparatus in the fish, may be therefore thus briefly stated :
What are the anatomical conditions, and the vital actions
(meaning by vital all the actions of whatever kind, performed
by the living structure), essential to the production of a
sensible current of electricity, such as is produced by the
apparatus in question ?
Here it becomes necessary to review the more important
successive opinions which have been taken of the electric
property of the apparatus. Walsh (Phil. Trans. 1773) con-
cluded that the electricity of the Torpedo resides in the
electric organs ; that their upper and under surfaces are
capable, from a state of electric equilibrium, of being instantly
thrown, "by a mere energy, into a plus and minus state, like
that of a charged phial ; and that the current results from a
conducting medium between their opposite surfaces being sup-
plied, naturally, by the medium in which the animal lives, or
artificially. The dependence of the electro-motor energy of the
apparatus on the nervous centre has been more distinctly stated
by Matteucci (Biblioth. Univ. xii.) and Dr. John Davy (Phil.
Trans. 1834), the batteries being therefore viewed as analo-
gous to Ley den jars, or an inductive apparatus. Eudolphi (loc.
ELECTRICAL OEGANS IN FISHES. 301
cit.) considered the perpendicular prisms in Torpedo as gal-
vanic piles, the horizontal series in Gymnotus as trough
arrangements ; but without entering into the details of the
comparison. This view of their action does not explain the
intermittent and voluntary character of the discharges. For,
as Valentin (loc. cit.) has stated, the organs in the fish cannot
be complete galvanic batteries, or they would be continually
charged, and a discharge would follow every suitable closure
of the circuit. Valentin (loc. cit.) proposes the following
theory of the apparatus, based on Moser's (Dove and Moser's
Repertorium der Physik, 1837) hypothesis of the action of the
fluid of the cells of the battery on the substance of the nerves
contained in it. He assumes the structure of the battery to
be a series of closed spaces ; the series enveloped in thicker,
the spaces separated by thinner aponeurotic laminae ; each
space being lined by a vascular epithelium, under which the
nervous plexuses lie ; and filled with fluid. He supposes
that there results from the organic or nutritive reactions of the
circulating blood, the epithelium, and the contained fluid of
each space, a certain amount of electric force, not, however,
sufficient to overcome the insulating obstacle opposed to it in
the aponeurotic walls ; all the spaces in the battery are,
therefore, so far only insulated electrical spaces. As soon,
however, as the will of the animal determines a flow of
nervous force into the spaces, the organic reactions become so
much exalted, that the resolved electric force overcomes the
insulating power of the laminae, and a current is produced
the current being confined to the series by their thicker
aponeurotic walls. This theory, although it may account for
a sudden increase of electricity in the organ, affords no ex-
planation of its progressive character; the current is not
accounted for.
The theory which most satisfactorily combines the ana-
tomico-physiological as well as the electrical phenomena of
302 ELECTRICAL ORGANS IN FISHES.
the apparatus, is that lately propounded by Professor Pacini
of Florence (Sulla struttura intima dell organo elettrico del
Gymnoto, e di altri pesci elettrici, 1852). Having discovered
the important anatomical fact, that the nerves are distributed
on one surface only of the electrical elements of the battery ;
while the vessels and nucleated cellular texture occupy the
other ; he finds in these structural peculiarities the condition
wanting in Valentin's theory an explanation of the progres-
sion of the electricity the current. Pacini refers the
electrical batteries in the fish to two forms of structure, and
two modes of action ; of the first and simplest form the Tor-
pedo affords the type, of the second and more complicated,
the Gymnotus. The batteries of Malapterurus are probably
referable to the Torpedinal type, those of Eaia certainly to
that of Gymnotus. In the Torpedinal type of battery, accord-
ing to Pacini, the action is analogous to that which takes
place in a thermo-electric pile, inasmuch as he conceives it to
depend upon a dynamical difference, a certain different con-
dition, in the two surfaces of each diaphragm of this Unary
type of pile. The nerve-surface and the vasculo-cellular sur-
face of a Torpedinal diaphragm correspond to the bismuth
and copper, or bismuth and antimony elements of a thermo-
electric arrangement ; the nervous influence in the former
taking the place of the heat applied in the latter. There is
here assumed, what on other grounds is highly probable, that
the electrical and nervous forces are correlative ; and here it
must be admitted that in Torpedo, as pointed out by John
Hunter (Phil. Trans. 1773), the bulk of the nerves in relation
to the batteries is much greater than in Gymnotus, which
exemplifies Pacini's second or ternary type of animal battery.
When the Torpedo, therefore, wills a shock, or when, through
the reflex action of its electrical nervous centre, a shock is
induced, a sudden and copious nervous influx flowing over the
under surfaces of its electric diaphragms, the upper surfaces
ELECTRICAL ORGANS IN FISHES. 303
are thrown into an opposite electrical condition, and a current
is the consequence.
Pacini refers the structure of the battery in Gymnotus to
a ternary type ; consisting of a negative element the fibrous
layer on which the nerves ramify, together with the fluid
which it bounds below ; a positive element the ridged
vasculo-cellular layer ; and a conducting element, the inter-
diaphragmatic fluid. The vasculo-cellular layer predominat-
ing in this ternary type over the nervous, Pacini conceives
the electricity to be evolved in the organic actions of the
vasculo-cellular layer under the influence of the nerves. In
other words, the will of the Gymnotus, or the reflex action of
its electrical nervous centre, directs an influence along the
nerves of its batteries over the fibro-nervous layer ; which
suddenly exciting the nutritive or other organic actions of the
highly-developed vasculo-cellular layer, an electrical disturb-
ance is produced ; with an opposite electrical condition of
the fibro-nervous and vasculo-cellular layers of the diaphragms,
and consequently a current through the series. Pacini com-
pares the wide-meshed fibrous layer, on the under surface of
which the nerves ramify to the hollow cylinder of porous clay,
which in a Bunsen's or Grove's galvanic arrangement separates
the negative from the positive elements.
As to the manner in which the animal avails itself of the
electrical currents which it has the power of exciting, without
alluding to the numerous experiments which have been made
on the Torpedo in air, I shall confine myself to the mode in
which the Torpedo and Gymnotus use their currents as means
of offence and defence in their proper aqueous medium. In
the first place, it is evident that in water, the currents between
the opposite surfaces of Torpedo, or between the ends of Gym-
notus, instead of being confined to a transverse area of limited
extent, as when they pass along a wire during a discharge in
the air, must be diffused through a considerable extent of
304 ELECTRICAL ORGANS IN FISHES.
the water surrounding the fish. The entire current force of
the batteries must, in fact, be subdivided into numerous sub-
ordinate axes of force arranged in lines which come round the
margins of Torpedo from back to belly, and along the sides of
Gymiiotus from head to tail. It is evident, therefore, that
another fish placed so that its antero-posterior axis is in the
line of inductive action in the water, will be affected less
powerfully by the circulating electric power than if it were
placed across these lines. Mr. Faraday (Phil. Trans. 1839)
found that although the Gymnotus can stun and kill fishes
which are in various positions in relation to its own body, it
can, moreover, by throwing itself so as to form a coil enclosing
the fish, the latter representing a diameter across it, so concen-
trate its currents of one side as to strike it motionless as if by
lightning. The Torpedo would also appear, from the observa-
tions of Dr. Davy, instinctively to elevate or arrange its
margin so as to adjust the direction of its currents to the
position of the object through which it wishes to pass them.
" Thus," as Mr. Faraday observes, " the very conducting power
which the water has ; that which it gives to the moistened
skin of the fish or animal to be struck ; the extent of surface
by which the fish and water conducting the charge to it are
in contact ; all conduce to favour and increase the shock upon
the doomed animal" (Phil. Trans. 1839). Here, it is to be
noted that one of the chief difficulties in explaining the
operation of the electrical apparatus in the fish has been the
necessity of admitting a certain amount of insulating property
in certain of the textures composing and surrounding it ; and
in conceiving the apparatus acting at all in a medium which
conducts so freely as water. The apparatus in fact owes its
efficiency in such a medium to its peculiar combination of
quantity and intensity. The battery of the fish, in relation to
its final purpose, is a perfect instrument ; yet, from another
point of view, and in one sense, when compared with an arti-
ELECTRICAL ORGANS IN FISHES. 305
ficial electrical apparatus, it is imperfect. It is necessarily
most insufficiently insulated, and there is, therefore, an enor-
mous loss of electricity ; but the quantity produced is com-
paratively so enormous that enough remains to form an
efficient circuit. It is, in fact, a remarkable example of the
munificent power and perfect freedom of action, in combina-
tion with strict adhesion to law, which distinguish the work
of the Creator in the formation and economy of organised
beings ; and it is only to be imitated in the most imperfect
manner by human ingenuity.
The presumed correlation of the nervous and electrical
forces in no way trenches on the psychical department of
physiology, and has no tendency to exclude the psychical or
proper vital element from the science of organisation. The
physiology of man, at all events, can only be successfully
studied and prosecuted by approaching it from two opposite
poles. From the one, we approach its somatic department
through anatomy, chemistry, and physics ; by the kind of
evidence and method of research common to all such sciences.
From the other, guided by an evidence and method totally
different in kind, we enter on its intellectual and moral de-
partments through philosophy and revelation.*
* This lecture was illustrated by a selection from the very complete series
of preparations of electrical organs in the Comparative Anatomy series in the
Museum of the University .
306 PRESENT STATE OF ORGANIC ELECTRICITY.
XVI. A BEIEF EEVIEW OF THE PEESENT STATE
OF ORGANIC ELECTRICITY.
THE general Theory of Electricity has rapidly approached a
consistent form through the labours of recent physicists and
particularly by the researches of Mr. Faraday. The hypo-
theses of one or of two electric fluids, however modified,
have been found tenable only so far as they involve the
idea of force. In the phenomena of statical as in those
of current electricity, there is constantly pressed upon the
observer the necessity of admitting two forces, or two
forms or directions of a force, inseparable from one another.
And thus " the influence which is present in an electrical
condition may best be conceived of as an axis of power
having contrary forces, exactly equal in amount, in contrary
directions." *
This peculiar form of force manifests itself in different
kinds of inorganic matter, under circumstances such as fric-
tion, change of temperature, magnetic influence, and chemical
action.
It is also manifested in organised beings, not only under
circumstances in which they stand related to it as masses of
mere matter ; but more particularly during the actions per-
formed by their component textures and organs.
Electrical science has been hitherto chiefly prosecuted in
the region of inorganic nature ; and although Volta opened
* Faraday, Philosophical Transactions; and Experimental Researches in
Electricity.
PRESENT STATE OF ORGANIC ELECTRICITY. 307
up a boundless field of discovery, yet organic electricity still
remains comparatively uncultivated.
In the investigation of electrical force as manifested in
organic nature, the peculiar economy of the organised being
must be taken into account. Each organised being, although
dependent on certain external circumstances as the conditions
of its existence, is, nevertheless, a system per se. Irrespective
of those electrical conditions into which it may be thrown,
through surrounding bodies, or through the medium in which
it lives, it undoubtedly contains more or less numerous sources
of electrical disturbance, in the numerous processes and
arrangements productive of currents in the structures which
collectively constitute its organisation. The organised being
may be considered electrically as a system of electrical currents
excited by electrical arrangements in the disposition of its
fluids, textures, and organs.
So far as has yet been ascertained, these electrical currents,
with the exception of those produced by the special batteries
in the electrical fishes, are not employed in the economy of
the being. They are merely necessary consequences of the
organic processes carried on by the different structures ; and
effect, by their arrangement, the distribution of the resulting
electricity, and the maintenance of the general electrical equi-
librium of the organic sytem. The detection and investigation
of these organic electrical phenomena are, however, important,
not only for general electrical science, but also for the eluci-
dation of the organic processes themselves. Eesidual pheno-
mena, as such electrical disturbances must generally be
considered in physiology, will, when investigated, indicate the
probable nature of the actions from which they result.
ELECTRICAL PHENOMENA IN VEGETABLES.
Various observers have proved the existence in plants of
arrangements which affect the condenser and galvanometer.
308 PEESENT STATE OF OKGANIC ELECTRICITY.
The experiments of Pouillet* on electricity developed in, or
in connection with, young plants in a state of growth, al-
though valuable, present too many sources of fallacy to be
available at present. Donne f was the first to point out the
opposite electrical conditions of different parts of vegetables.
He found the opposite extremities of certain fruits, and even
the juices removed from those parts, to be in different electri-
cal states ; and thus opened up a new field of organic electri-
city, which promises, when more fully investigated, to lead to
important results. The most precise information, however,
regarding the effect of different parts of vegetables on the gal-
vanometer are contained in two communications by M.
Becquerel in the Memoirs of the French Academy, \ and in a
notice by Professor Wartmann in the Bibliotlieque Universelle
de G-eneve$ The researches themselves are not yet suffi-
ciently advanced to admit of a satisfactory analysis. Indeed,
as M. Becquerel observes, the electrical effects are so complex
that it is unsafe to draw any conclusion regarding the part
which electricity takes in the organic functions. Hitherto,
therefore, in his researches, he has considered electricity
rather as an effect, serving to elucidate the study of physiology,
than as a primary cause of organic phenomena. Much diffi-
culty exists in determining whether certain currents, indi-
cated by the instrument, are primary or derived ; and also in
ascertaining how far the observed currents are produced by
* " Sur 1'Electricite des fluides elastiques, et sur une des causes de 1'Elec-
tricite de 1' Atmosphere. " Ann. de Ckim. et de Physique, torn. xxxv. 1827.
t " Kecherches sur quelques unes des Proprietes Chimiques des secretions
et sur les courants electriques qui existent dans les Corps Organizes." Ann.
de Cliim. et de Physique, torn. Ivii. 1834.
J " Kecherches sur les causes qui degagent de I'electricite dans les vegetaux,
et sur les courants vegetaux terrestres;" and "Memoire sur les effets elec-
triques obtenus dans les tubercules, les racines, et les fruits, an moyen d'ai-
guilles de platine. " Mem. de I'Acad. des Sciences, torn, xxiii.
"Note sur les Courants electriques qui existent dans les vegetaux. "-
Bibliothequc Universelle de Geneve, torn. xv. 1850.
PRESENT STATE OF ORGANIC ELECTRICITY. 309
unavoidable injury of texture, and consequent mixing of fluids,
by the insertion of the platina electrodes. The progress of
animal electricity had, previously to the labours of Du Bois
Keymond,* been impeded by similar circumstances ; and
until the electro-motor properties of the component parts of
vegetables are in some way separately investigated, as those of
muscle and nerve have been by the observer alluded to, no
solid progress can be looked for in vegetable electricity.
The general arrangement of the parts of a plant, and the
functions they perform, indicate the probable direction of the
resulting electrical disturbances. The differences in the con-
stitution of the ascending and descending portions of the axis,
and of their different transverse segments, naturally indicate
the existence of longitudinal currents ; while the structural
and functional differences between the central and superficial
portions of the axis point to transverse or radiating lines of
force. Accordingly, all the observations of Donne, Becquerel,
and Wartmann, indicate currents, primary or derived, in the
longitudinal and transverse direction, in roots, tubers, stems,
leaves, flowers and fruits.
The Electrical Reactions of the Plant, Soil, and Atmosphere.
The soil is in a constant negative, while the air, when calm
and free from clouds, is in a positive, electric condition.
According to the experiments of Pouillet,t plants in the
later stages of germination, after they have protruded from
the soil, exhibit, by the condenser, an excess of negative elec-
tricity. The explanation he gives is, according to Becquerel,]:
probably correct ; that the action of the oxygen of the air on
the starch of the seed, during its conversion, gives an excess of
positive electricity to the air, and of negative electricity to the
Poggendorff's Annalen, and Untersuchungen uber Thierische Electri-
titcit, 1848.
t Ann. de Chim. et de Physique, loc. cit.
% Mem. de I'Acad. des Sciences, torn, xxiii. p. GO.
310 PKESENT STATE OF ORGANIC ELECTRICITY,
plant and soil The electrical effects observed by M. Pouillet,
in this first period of vegetation, correspond with the ordinary
electrical conditions of the earth and atmosphere.
But according to M. Becquerel's own observations,* the
electrical relations of the plant to the soil and air are reversed
after germination is completed. If the electrodes of the gal-
vanometer are inserted the one into the stem or branch, or
passed through a number of leaves laid together, but still
adherent, the other into the soil the former will exhibit an
excess of negative, the latter of positive electricity, in propor-
tion to the humidity of the soil and the succulence of the
plant.
It may, therefore, be presumed that in the act of vegetation,
after germination is accomplished, the ascending sap, which
communicates by means of the root with the soil, conveys to
it continuously the excess of positive electricity which it has
acquired during its course upwards in its reactions more par-
ticularly with the descending sap ; while the latter furnishes
to the air, by exhalation, its excess of negative electricity.
Vegetation, therefore, produces electric effects contrary to
those which render the air and soil respectively positive and
negative.
Longitudinal Electrical Currents in the Dicotyledonous Plant.
Becquerel states t that if the electrodes of the galvanometer
be inserted transversely into the parenchyma of the bark, the
one a certain distance above the other, or if one be inserted
between the bark and wood, and the other be passed through
a number of leaves, superimposed and still adherent, the
needle will indicate a current passing from below up wards J
* Mem. de I'Acad. des Sciences, torn, xxiii. pp. 61, 62.
t Ibid., torn, xxiii. pp. 55, 56.
J The statement of the direction of an electrical current is a conventional
form of expression, which ought to convey merely an indication of the relative
positions of its positive and negative extremities, and consequently of the two
polar forces, both of which exist in the current. In the circuit formed by the
PRESENT STATE OF ORGANIC ELECTRICITY. 311
through the parenchyma, the upper electrode indicating posi-
tive, the lower negative electricity. M. Becquerel accounts
for the relative electrical conditions of the green parenchyma
from the leaves downwards by the removal of oxygen.
But the observations of M. Becquerel on the relative elec-
trical conditions of the plant and soil indicate the existence
of a descending current passing from the stem through the
roots into the earth, which therefore becomes positive around
the plant.
M. Wartmann, in the notice already quoted,* states that
in the roots, the stem, the branches, the petioles, and peduncles,
there exist a central descending current, and a peripheral
ascending one, which he denominates axial currents ; and that
the galvanometer indicates currents from every part of the
plant, aerial or subterranean, to the soil, which is thus positive
in relation to the plant.
From these observations of Becquerel and Wartmann, little
doubt can be entertained that electrical currents exist in the
dicotyledonous plant, in the course of the circulation of its
sap, but in an opposite direction to it.
Currents passing from within outwards, and from without
inwards in the horizontal section of the Dicotyledonous Plant.
According to Becquerel,t if one electrode be inserted into the
pith, in a clean horizontal section of a young poplar, and the
other into one of the woody layers, or into the bark, the needle
is deflected 5, 10, 15, or more, according to the delicacy of
galvanometer, the current which traverses its wire, and which deflects the
magnetic needle, is conventionally said to pass from the positive to the nega-
tive electrode ; while in the electro-motor portion of the circuit e.g. a portion
of vegetable structure the current is said to pass in the opposite direction.
But "there is never one current of force, .or one fluid only." " In a current,
whatever form the discharge may take, or whatever part of the circuit or
current is referred to, as much positive force as is there exerted in one direction,
so much negative force is there exerted in the other."
* Bib. Univ. de Geneve, torn. xv. p. 302.
t Loc. at. p. 44.
312 .PRESENT STATE OF ORGANIC ELECTRICITY.
the instrument, the succulence of the tree, or the radial
distance of the layer into which the second electrode has
been inserted ; a current from without inwards is indicated,
the electrode in the pith being positive, that in the wood or
bark negative.
If the one electrode be inserted close to the outside, and
the other be removed from the pith, and be reinserted from
place to place outwards, the current will diminish in intensity
as the second electrode approaches the cambium. Beyond
the cambium the current changes its direction and becomes
stronger. The current which now deflects the needle passes
along the wire from without inwards, indicating a positive
electric condition of the outer part of the parenchyma, and a
negative condition of the cambium.
On removing a piece of bark, and applying the electrodes,
(which in this experiment should consist of platinum plates)
to its opposite surfaces, the current becomes very intense. The
piece of bark thus forms a voltaic couple, of which the ex-
terior or parenchymatous side is positive, and the interior,
covered by the cambium, negative.
It would appear then that, from the pith to the cambium,
the woody layers are less and less positive in relation to the
pith ; whilst from the cambium to the cuticle, the parenchy-
matous layers are more positive, or at least comport themselves
as such in the production of derived currents. This inversion
of the electrical effects corresponds with the relative position
of the cellular texture in the bark and wood. In the bark, it
is on the exterior ; in the wood, in the interior ; in both it is
positive.
In the notice by M. Wartmann, in the Bibliothbque Vni-
verselle de Gen&ve* that observer states that " in uniting by
the galvanometer the layers of the stem where the liber and
cambium touch one another (and where many botanists admit
* Sib. Univ. de Gentve, torn. xv. p. 301.
PRESENT STATE OF ORGANIC ELECTRICITY. 313
a passage of descending juices), either with the most central
parts (the pith or the perfect wood), or with the parts more
exterior (the young bark), a lateral current will be found
tending from these layers to the neighbouring organs."
It would appear, therefore, that currents pass from the
contiguous surfaces of the bark and wood of the dicotyle-
donous plant outwards towards the cuticle, and inwards to
the pith ; or at least, arrangements exist in these directions
which excite currents in the opposite directions through the
galvanometer wire.
Currents in the Eoot and its Dependencies. According to
M. Wartmann,* in some roots the central structures and the
cortical structures are, as in the stem, positive in relation to
the layers by which they touch and are united.
Centrifugal transverse currents would appear to exist in
certain roots, which resemble tubers in the quantity of their
nutritious deposits. For Becquerelf has found the central
part of the carrot, and of the red and white beetroot, negative
in relation to the exterior.
In the potato, in the tubers of the HeliantJius tuberosus
and Lafhyrus tulerosus, currents radiate from the centre to
the cuticle ; for the electrode at the centre is negative in
relation to the other, the latter indicating a more positive
condition the nearer it is placed to the cuticle. Becquerel,
who has ascertained these facts, and refers them to the system
of transverse currents in the bark, states at the same time
that in the tubers of Tropceolum tuberosum, and Ullucus
tuberosus, the currents are reversed, and correspond, there-
fore, with the transverse system in the wood and pith of the
dicotyledonous stem.
* Bib. Univ. de Geneve, torn. xv.
t Memoire sur les effets electriques obtenus dans les tubercules, les racines,
" etles fruits, an moyen d'aiguilles de platine." Mem. de I'Acad. des Sciences,
torn, xxiii.
314 PRESENT STATE OF ORGANIC ELECTRICITY.
It remains to be determined how far the single transverse
system of electrical currents in either direction, in certain
roots, and in tubers, depends upon the disappearance of the
central or peripheral elements of the axis.
On Currents in Leaves. The relations and functions of the
leaf indicate the probable direction of the electrical currents
which may exist in it.
Becquerel's * observations lead to the conclusion that cur-
rents set from the cambium to the parenchyma of the leaf ;
while at the same time it is negative in relation to the pith
and wood of the branch and stem. He states that the leaves
comport themselves as the green part of the parenchyma of
the bark that is to say, the sap which circulates in their
tissues is negative in relation to the wood, pith, and soil ; and
positive in relation to the cambium.
M. Wartmann-f- states that in most leaves the currents
proceed from the limb of the leaf to its veins, and to the
central parts of its petiole, and of the stem.
This centripetal current attributed to the leaf by Becquerel
and Wartmann is evidently referable to the central or de-
scending axial current of the plant ; while the centrifugal
current alluded to by the former belongs to the superficial
transverse system, or that between the inner and outer aspects
of the bark
The Electrical Condition of the Flower. From the energetic
actions and rapid development of the flower, a considerable
amount of electrical disturbance is to be expected in it.
Various observers have ascertained the remarkable elevation
of temperature which occurs during the development of this
part of the plant ; and the important chemico-vital actions
which take place in it must certainly excite corresponding
electrical phenomena.
* " Kecherches sur les causes qui degagent de I'electricite, " etc. Mem. de
VAcad. de Sciences, torn, xxiii.
*h Bibliotheque Universelle de Geneve, torn. xv.
PRESENT STATE OF ORGANIC ELECTRICITY. 315
The only observations in regard to these which have been
recorded are by Zantedeschi, quoted by Becquerel in his second
memoir.* The Italian observer found that at the period of
flowering in the tulip, jonquil, and anemone, a deflection of
the needle to the extent of 3 or 4, due to a descending cur-
rent, occurs. He also found in an Azalea, an Amaryllis, a
white lily, and in various species of Opuntia, a current passing
from the stamen to the pistil ; the one electrode being in
contact with the pollen, the other inserted into the stigma.
Electrical condition of the Fruit. The only recorded ob-
servations on this subject are by DonneVf* in a memoir which
may be said to have introduced for the first time the subject
of vegetable, as well as certain important departments of
animal electricity.
Donne" found that when the platinum extremities of the
galvanometer wire are plunged into certain fruits, the one at
the stalk, the other at the opposite end, the parts exhibit
different electrical conditions. In the apple and pear a
current would appear to pass from the stalk towards the eye
at the opposite end; whilst in the peach and apricot the
current passes in the contrary direction. In the apple and
pear the fruit is electro-positive at the distal end, electro-
negative at the stalk ; the contrary being the case in the
peach and apricot.
Irrespective of the chemical causes to which these currents
are ascribed by Donne' and Becquerel, it might be well to
determine how far their opposite directions may be referable
to morphological differences in the two forms of fruit examined :
whether in the monocarpal form, as in the peach, the current
be not referable to the centripetal current of the leaf ; and
whether in the apple form (the fleshy mass of which is not a
h " Memoire sur les effects electriques, " etc. Mem. de VAcad. de Sciences,
torn, xxiii.
t Ann. de Chim. et de Physique, torn. Ivii.
316 PRESENT STATE OF ORGANIC ELECTRICITY.
development of the carpellary leaf, but of the cortical layer of
the receptacle, and of the end of the peduncle) it is not due to
the same causes which produce the general superficial, or
cortical axial current in the plant.
Are the Currents which affect the Galvanometer derived from
Currents which actually exist in the Plant ? or are they pro-
duced by the Insertion of the Electrodes ? M. Becquerel ex-
presses himself very cautiously on this point ; and blames
certain physicists for entertaining inexact ideas regarding the
currents obtained from organised bodies by the galvanometer
platinum wires ; and for assuming that such currents are
necessarily derived from other currents which actually exist
in the plant. But M. Becquerel adds,* somewhat inconsist-
ently with his own admissions in other parts of his memoirs,
that nothing at present authorises an induction of this kind.
The effects, he states, appear to be due, at least in most cases,
to the reaction of different liquids in contact with the elec-
trodes ; from which results such a disengagement of electricity,
as that the liquid, which comports itself as an acid in relation
to the other, sets free positive electricity.
At the same time, M. Becquerel admits that the two neces-
sary conditions for the production of primary currents exist
in the plant. The first is, that two liquids capable of acting
chemically on one another should be arranged so as to do so
gradually and continuously, or that there should be, as M.
Becquerel expresses it, a le contact des deux liquides per
transition insensible." The other is the intermedium of a
conducting texture, or substance to complete the circuit. M.
Becquerel, accordingly, both in his memoirs f and in his
abridgments in the Comptes Rendus^ seems inclined to admit
the two axial currents, and the horizontal system in the stem
and branches of the dicotyledonous plant. Beyond this he
* Mem. de I'Acad. des Sciences, torn, xxiii. t Ibid.
+ Comptes Rendiis, torn. xxxi. xxxii.
PEESENT STATE OF ORGANIC ELECTRICITY. 3 IT
appears, at the date of the publication of his memoirs, to have
drawn no more precise conclusion from the facts then ob-
served ; and states that the electrical effects which take place
in vegetables are so numerous, that it has only been possible
hitherto to observe a limited number of them.
M. Wartmann,* while he admits that the electro-chemical
action, which results from the tearing of the textures during
the insertion of the electrodes, produces at first a considerable
deflection of the needle, states, at the same time, that when
this action ceases, which it speedily does, there remains a more
feeble current, which must be due to the normal electrical
action of the parts. He states that vegetable currents pro-
bably form closed circuits ; that the extremities of the root-
fibres on the one hand, and the terminations of the leaves on
the other, establish a continuity between the ascending peri-
pheral and the descending central current ; while the simi-
larity in the electrical condition of the exterior of the bark
and the interior of the wood probably depends on the medul-
lary rays.
To what Actions and Arrangements in the Plant are its
Electrical Disturbances and Currents due ? From what has
already been stated, it must appear that the knowledge
hitherto obtained of the relations and circumstances of the
electrical disturbances and currents in the plant is not yet
sufficiently precise to afford a solution of this question. Be-
fore the publication of Du Bois Eeymond's researches on the
electrical actions of muscle and nerve, and of Pacini on the
structure of the batteries in the Torpedo and Gymnotus, elec-
trical excitement in the animal body had not been accurately
connected with anatomical structure ; and until" a definite
electrical current in the plant is distinctly referred to a demon-
strable structural arrangement, a precise determination of the
exciting causes of currents in the latter cannot be expected.
* Bib. Univ. de Geneve, torn. xv.
318 PRESENT STATE OF ORGANIC ELECTRICITY.
We are not, indeed, acquainted with the actual chemical or
physical causes of electrical excitement in any animal texture
or organ ; but we now know the direction and relations of the
current in and to the anatomical structure in certain cases.
This is a secure step in the proper direction, and one which
has yet to be taken in vegetable electricity.
At present, therefore, it can only be stated generally that
the disturbance of electric equilibrium in the textures and
organs of the plant is due to the chemical action which plays
so important a part in the organic processes at its surface, as
during transpiration, respiration proper, and the fixation of
carbon and in its interior, during the reaction of its ascend-
ing and descending sap, with the substances contained in the
cells of its various structures. In the same manner, no precise
statement can be made at present regarding the arrangements
by means of which electrical currents are produced in the
plant. The researches of Becquerel* have proved that a
current is produced when two liquids of acid and alkaline re-
actions respectively, and separated from one another by a
porous substance, are connected either by a fluid or solid con-
ductor. It is quite evident that similar physical and chemical
conditions for the production of currents exist in innumerable
forms in the organisation of vegetables. It is, however, im-
possible in the present phase of the subject to define them
with greater precision.
ANIMAL ELECTRICITY.
The first discovery in animal electricity was the deter-
mination of the electrical character of the shock of the
Torpedo by Walsh in 1772. The development of the sub-
ject has since been retarded, not only by its own intrinsic
difficulty, but also by the greater attractions of those depart-
ments of general electricity which were opened up by
* " Recherches sur les circuits electro-chimique simple forme de liquides."
Comptes Rewdus, torn. xxiv.
PKESENT STATE OF ORGANIC ELECTRICITY. 319
the labours of Volta. Its history presents three distinct lines
of research that of the special electrical organs of the fish,
commencing with the discovery of Walsh in 1772,* that of
the electrical properties of muscle and nerve, starting from
the fundamental experiment of Galvani in 1786-94,1 and that
of the electrical phenomena of membranes and glands, intro-
duced by Donne* in 1834 1
The results which have ultimately been attained in these
three directions will now be briefly examined ; but in order to
obtain a more comprehensive view they shall be taken up in
the reverse order.
Electric PJienomena in connection with MEMBRANE and
GLAND. The experiments of Donne are now alluded to only
because they were the first which proved electric disturbance
in connection with secreting membrane and structure. He
found that when the electrodes of the galvanometer were
applied respectively to the mucous membrane of the mouth
and to the skin, the needle deviated 15, 20, or 30 ; the
former being negative, the latter positive. In the same
manner, when the instrument was applied between the mucous
membrane of the stomach and the gall-bladder, or interior of
the liver, the needle deviated 30, .40, or 50.
Donne* attributed these electric effects to the acid and alka-
line properties of the secretions with which the electrodes
were respectively in contact. Matteucci, again, while ad-
mitting the correctness of Donnas experimental results, attri-
buted, as Drs. Wollaston 1 1 and Thomas Young IF had previously
* " Of the Electric Property of the Torpedo. "Phil. Trans. 1773.
t DC Viribus Electricitatis in Motu Musculari Commentarius ; Bologna,
1791.
t Ann. de Chim. et de Phys. torn. Ivii. 1834.
Ibid. torn. Ivi.
II Phil. Mag. vol. xxxiii. " On the Agency of Electricity on Animal Secre-
tions."
II Young. Syllabus of Lectures on Medicine.
320 PRESENT STATE OF ORGANIC ELECTRICITY.
done, the difference of the chemical composition of the secre-
tions to the electric force itself. It is evident, therefore, that
the ingenious conjectures of Wollaston and Young, and the
experiments of Donne and Matteucci, merely indicated a
promising field of discovery, and formed a prelude to researches
which promised more precise results after the structures
experimented upon had been more definitely selected.
The Electric Relations of Mucous Membrane. Mr. H. F.
Baxter has recorded the results of his experiments on this sub-
ject.* The principal object Mr. Baxter had in view was to
determine the relative electric condition of the secretions of
the mucous membrane, and of its vessels and blood ; fulfil-
ling, therefore, what has already been stated as an apparent
condition of success in all such inquiries viz. experimenting,
as far as can be, on distinct textures or organs, and not on
their aggregations.
The mucous membrane of the stomachs, and of the small
and large intestines, of the rabbit, cat, and guinea-pig, were
selected ; and pointed and flattened platinum electrodes ap-
plied respectively to the surface of the mucous membrane,
and inserted into the vessels. The following were the general
results :
1. The inside and outside of the gut were formed into a
circuit without effect.
2. One electrode on the mucous membrane, the other
inserted into an artery proceeding to the same spot, produced
no effect.
3. One electrode on the mucous membrane, the other in-
serted into a vein proceeding from the same spot, indicated a
positive condition of the vein or its contents, by a deviation
of the needle to the extent of from 3 to 5.
* Phil. Trans. 1848. "An experimental inquiry, undertaken with a view
of ascertaining whether any, or what, signs of current electricity are manifested
during the organic process of secretion, in living animals," etc.
PRESENT STATE OF ORGANIC ELECTRICITY. 321
4. One electrode on the mucous membrane, the other in-
serted into a vein emptied of its blood, produced no effect.
5. One electrode applied to the mucous membrane, the
other inserted into a vein not proceeding from the same spot,
produced no effect.
6. It was not necessary to insert the second electrode into
the vein, for the needle was deflected if the second electrode
was merely dipped into the blood flowing from the vein.
Having ascertained how far the different solid and fluid
substances in contact with the electrodes might interfere
with the result, and also in what manner the effects were in-
fluenced by the death of the animal, Mr. Baxter concluded
from his experiments, that
1. When the electrodes of a galvanometer are brought
into communication one with the mucous membrane of the
alimentary canal, the other with the blood flowing from the
same part a deviation of the needle takes place, indicating
that the secreted product and the blood are in opposite electric
states.
2. The effect occurs during the life of the animal, and
ceases after its death.
3. The effect may be considered as arising from the de-
composition of the blood i.e. from the changes which occur
during the formation of the secreted product and venous blood.
4 These changes are effected by the organic actions of
the part.
The Electric Relations of Gland. In a second paper,* Mr.
Baxter records the experiments which he had made to deter-
mine the electric relations of the secretions and blood of the
liver, kidney, and mammary gland. The facts which his ex-
periments tend to establish are as follow :
* Phil. Trans. 1852. An experimental inquiry undertaken with a view
of ascertaining whether any, or what, signs of current electricity are manifested
during the organic process of secretion in living animals, etc.
Y
322 PRESENT STATE OF ORGANIC ELECTRICITY.
1. During biliary secretion, the Hie and venous Uood flow-
ing from the hepatic veins are in opposite electric states.
2. During urinary secretion, the urine and venous Uood
flowing from the renal vein are in opposite electric states.
3. During mammary secretion, the milk and the venous
Uood flowing from the mammary veins, are in opposite electric
states.
In these experiments on glandular action, as in those de-
scribed above on the alimentary mucous membrane, the venous
blood was found to be positive, producing a deflection of the
needle to the extent of 3, 4, 5, 8, 10.
Tlie Electric Relations of the Respiratory Mucous Membrane
and the Pulmonic Blood. Mr. Baxter, having ascertained that
the venous blood flowing from a secreting membrane or gland,
is in a positive electric condition, applied one electrode in
contact with the mucous membrane of the lung, and the other
in contact with the blood flowing from it i.e. the arterial blood.
He thus found the blood of the pulmonary veins, or of the
left ventricle, invariably positive, producing a deflection of
2, 3, 4, or 5. At the same time, he ascertained that when
the respiratory mucous membrane and the blood of the right
ventricle are connected, a deflection of 2, 3, or 4, occasionally
occurred. All his experiments tended to the same conclusion
viz. that the blood of the pulmonary veins is* positive ; and
that when a circuit is formed between the mucous membrane
of the lung, and the blood in the left ventricle of the heart,
a current is produced.
Tlie Electric Properties of MUSCLE. Galvani having dis-
covered and investigated the contractions produced by elec-
tricity in the muscles of the frog, * afterwards observed similar
contractions when two dissimilar metals, in contact with one
another, are also brought into contact with the nerve and
muscles respectively of the frog's leg.-f At first he appears to
* De Viribus Electricitatis, etc. t Ibid.
PRESENT STATE OF ORGANIC ELECTRICITY. 323
have conceived the contractions to be due to electricity evolved
by the metals ; but finally he concluded that it is produced
by the animal textures themselves. The researches of Yolta
verified the original opinion of Galvani, that the metals, when
they are employed, are the sources of the electricity which
produce the muscular contractions ;* but the discovery of the
pile, with its consequences, threw into temporary oblivion the
actual evidences of an electromotor property of the animal
textures independently of metals, which the numerous expe-
riments of Galvani and his supporters had afforded.f Even
Humboldt's observations did not prevent the almost total ne-
glect of the subject for a quarter of a century. J
In 1827, Nobili, || having applied his improved galvanometer
to the fundamental experiment of Galvani, discovered the elec-
tric current of the frog. He found that when the circuit of
the nerve and muscles of the leg is closed by the instrument,
a deviation of the needle to the extent of 10, 20, or 30, oc-
curs, due to a current which passes in the limb from the toes
upwards, and which could be increased by inclosing in the
circuit several frogs arranged as a battery. There could no
longer be any doubt of the truth of Galvani's later opinion,
that electricity is developed in connection with muscle and
nerve.
The researches of Matteucci, carried on during a transi-
tionary stage of the subject, and exhibiting occasional ob-
scurity and contradiction, are, nevertheless, valuable, not only
from having directed attention generally to electro-physiology,
but particularly from having, in regard to muscle, indicated
that its electric properties are due to its own texture, and not to
the conjoined nerves. He had always, however, experimented
* Nuova Memoria dell' Electricita Animate, etc.
+ Dell' UAO e dell' attivitd dell' arco conduttore nei contrazione de 1 muscoli,
1793 ; and Supplimento al Tratatto dell' uso, etc. 1794.
$. Versuche ueber die gcreizte MusJcel-und Nervenfaser, u. s. w., 1797.
|| Ann. de Chim. et de Phys. 1828
324 PEESENT STATE OF ORGANIC ELECTRICITY.
with masses, or aggregates of muscle, and had not attempted
to ascertain the laws of electric action in the muscular fibre
or bundle itself, or in a single isolated muscle.*
These laws have been investigated by Du Bois Eeymond,
who has ascertained that muscular structure presents two
distinct electric conditions firstly, during the intervals of
contractions ; and secondly, during contraction.
Electric Condition of a Muscle during the intervals of con-
traction. Galvani conceived the outer surface of a muscle to
be charged with negative, the inner with positive electricity.
Matteucci had found that in order to produce contractions in
the galvanoscopic frog, two parts of its nerve must be brought
into contact with two parts respectively of the muscle of a
living animal ; and that the experiment uniformly succeeded
if the nerve touched the bottom of a wound in the muscle and
the margin of the wound at the same time. Du Bois Eey-
mond has ascertained the actual relative electric condition of
certain surfaces or aspects of the muscular fibre or muscle.t
These aspects he denominates the longitudinal and transverse
sections. These sections, again, may be either natural or
artificial.
The natural longitudinal section is as much of the surface
of a muscle as is formed by the exposed sides of its superficial
fibres.
An artificial longitudinal section is any surface exposed
by a section in the direction of the muscular fibres.
The surface or side of a fibre or fasciculus viewed as a
cylinder or prism is its longitudinal section.
A natural transverse section is any part of a muscle formed
by the extremities of its fibres, coated by tendon of attachment.
* Bib. Univ. de Geneve; Ann. de Ckim. et de Phys. ; Traite des Pheno-
m&nes Electro-physiologique.
t " The Law of the Muscular Current," p. 498, vol. i. of Untersuch. ueber
Thier. Elcctridtdt.
PRESENT STATE OF ORGANIC ELECTRICITY. 325
An artificial transverse section is a section made at right
angles to the fibres.
The natural or artificial extremities of fibres are transverse
sections.
By employing a very delicate galvanometer, and by certain
refined precautions in the arrangement of his experiments,
Du Bois Eeymond found that the longitudinal section, natural
or artificial, is invariably positive in relation to the natural
or artificial transverse section. The following are the general
laws of the derived muscular current.
1. If any point of the natural or artificial longitudinal
section be put into connection, by means of the galvanometer,
with any point of the natural or artificial transverse section,
the needle will indicate a current in the wire from the longi-
tudinal to the transverse section.
2. If one point of the natural or artificial transverse section
of a muscle is brought into connection with another point of
the same or of another similar transverse section, and if the
points be unequally distant from the centre of the section
considered as the base of a muscular cylinder, a current is
indicated passing from the electrode furthest from the centre,
and directed to that which is nearest to it.
3. If we now consider the mass of the muscle as a cylinder,
and connect a point of the natural or artificial longitudinal
section nearer the middle transverse section of the mass, with
a point of the natural or artificial longitudinal section more
distant from the middle, a current is indicated passing from
the nearer to the more distant point.
4. If both connected points of one or of two natural or
artificial transverse sections be equally distant from the centre
of the surface, no current is indicated. So also in regard to
longitudinal sections, points equally distant from the middle
produced no current.
These laws are most satisfactorily illustrated in the muscles
326 PRESENT STATE OF ORGANIC ELECTRICITY.
of rabbits and frogs, but they are essentially the same in man,
in representatives of the four vertebrate classes, and in molluscs,
crustaceans, and annelids.
The electromotor power, which is exhibited in the muscular
current, does not depend upon the areolar texture, the tendons
or vessels, etc., of the mass ; or on the contact of dissimilar
textures with the muscular fibre ; for the power is exhibited
when the smallest manageable portion, or even a single primary
fasciculus, is employed. The power evidently resides in the
ultimate fibre.
Du Bois Eeymond has investigated the arrangement of the
electromotor elements on which this power depends. After
various experiments, he succeeded in constructing a model
consisting of a solid copper cylinder, with its cylindrical sur-
face coated with zinc, and suspended in or surrounded by an
electrolytic liquid, which fulfilled by means of the galvanometer
all the conditions of the current as derived from the natural
sections of an entire muscle. He arranged another model,
consisting of a number of similar but smaller cylinders, set in
longitudinal series, so that the positive or zinc elements were
directed laterally, and the copper or negative in the longitudinal
direction. A combination of this kind, immersed in a fluid,
exhibited by means of the galvanometer not only the currents
of the natural section of an entire muscle, but also the currents
of its artificial sections. Du Bois Eeymond, therefore, con-
cluded, that the conditions of the muscular current are fulfilled
by assuming in the muscular mass the existence of electromotor
centres, each of which may be conceived to be a molecule
consisting of an equatorial positive zone and two polar negative
zones, these molecules being arranged linearly, so that the
polar zones are in the direction of the muscular fibre.
These investigations in no way anticipate the cause of tlie
electromotor property of the muscular fibre ; they bear only on
the laws of its action. They leave very little doubt that the
.PRESENT STATE OF ORGANIC ELECTRICITY. 327
muscular substance during its life, and in the intervals of
contraction, is in a state of electric tension ; and that there
are in it an infinite number of electromotor centres in connec-
tion with closed circuits, according to the laws already stated ;
and which must be infinitely stronger than those derived
currents which are procured from a muscle, or a portion of it,
by means of the galvanometer.
Du Bois Eeymond having observed that the current de-
rived from a longitudinal section and from a natural transverse
section was generally weaker than that from an artificial trans-
verse section, and that it was even occasionally not obtainable
when the electric tension of the muscle was much diminished
by cold, found, on further investigation, that it was necessary
to admit the existence of a layer of peculiar electromotor
elements at the ends of the muscular fibres in contact with
the tendon. He denominates this the parelectronomic layer,
as it produces a current opposed to the general muscular
current, and must therefore present its positive elements
towards the tendon. Tor the purpose of including this layer
in his general theory, he modifies his conception of the elec-
tromotor molecules, and illustrates the entire action by a cor-
responding change in his model. Instead of the molecules
being, as he had denominated them, peripolar possessing an
equatorial positive and two polar negative zones, he substi-
tutes for each of such molecules a pair of dipolar molecules
with their positive poles in contact, and their negative directed
away from one another. If, now, the parelectronomic layer be
conceived as formed of one set only of such dipolar molecules,
they must necessarily have their positive poles next the ten-
dinous surface.
This hypothesis not only satisfies the general law of the
muscular current, but also affords a reason for the counteract-
ing influence of the natural transverse section, and the facility
328 PRESENT STATE OF ORGANIC ELECTRICITY.
with which it can be removed by any fluid which corrodes or
acts upon the muscular fibre, or by the knife.*
The general Muscular Current. Nobili discovered, by
means of the galvanometer, that a current passed from the
toes towards the head of the frog. If the animal be deprived
of its skin, and bent backwards so that its feet dip into one
vessel and its snout into another, the vessels being filled with
a saturated solution of common salt, and connected by the
electrodes, the needle will indicate a current in the galvano-
meter wire from the head to the feet. According to Du Bois
Eeymond, the general current may, by certain precautions, be
detected even in the undissected frog, although the circuit is
partially closed by the skin. This current is the resultant of
the currents of all the individual muscles of the frog ; for Du
Bois Eeymond found, firstly, that in some muscles the cur-
rents set from head to feet, in others in the opposite direction ;
secondly, that the electromotor power of a muscle is directly
as its length and thickness ; and, thirdly, that if two muscles
are opposed to one another in a circuit, the thicker or the
longer overcomes the other.
This general muscular current must therefore exist in every
animal possessing muscular arrangements, at least in the four
vertebrate classes. It does not, however, necessarily assume
the same general direction in all.f
Electric condition of a Muscle during Contraction. This
condition has not yet been accurately determined. Matteucci
observed, that when two prepared frog's limbs are so arranged
that the nerve of the one lies across the muscles of the other,
muscular contraction of the latter induces contraction of the
* The muscular current is investigated at great length, historically and
experimentally, in the second and third chapters of section iii. of Du Bois
Raymond's Untersuchungen.
f The fourth chapter of section iii., in the first part of vol. ii. of the Un-
tersitchungen, treats " Of the influence of Contraction on the Muscular Cur-
rent."
PRESENT STATE OF ORGANIC ELECTRICITY. 329
former. He concluded therefore, along with Becquerel, that
during muscular contraction there is an evolution of electri-
city. But the galvanometer, even when a pile of contracting
limbs is included in the circuit, gives no decided indication of
a current. Matteucci, indeed, has latterly denied the evolu-
tion of electricity during muscular contraction, and is inclined
to attribute the secondary contraction to another cause. Du
Bois Eeymond concludes from his investigations, that during
contraction the ordinary muscular current is much diminished,
if indeed it does not altogether disappear.
The contraction produced by a single act of excitement of
a striped muscle is momentary. Any change, therefore, of its
ordinary electric condition during such a contraction is too
brief to be satisfactorily indicated by the needle. But if a
muscle be included in the circuit of the galvanometer, and if,
as soon as the deflected needle comes to rest under the influ-
ence of the ordinary muscular current, the muscle be put into
a state of continuous contraction, or tetanus, by means of
strychnine, or an interrupted electric current, the needle will
pass backwards beyond zero, and oscillate unsteadily on the
negative side till the muscular contractility is exhausted. That
this negative deflection is not the result of any influence
exerted by the current employed to tetanise the muscles, is
shown by the fact that it occurs even when precautions are
taken to prevent such an influence ; and also by its occurrence
when the tetanus is produced by strychnine, and other non-
electric means.
If, again, an arrangement be made so as to enable the gal-
vanometer circuit to be closed as soon only as the tetanus has
commenced, the needle will be found, during the contraction,
only to approach zero more or less, instead of passing to the
negative side, indicating therefore a diminution of the ordinary
muscular current.
That this diminution in the ordinary muscular current is
330 PRESENT STATE OF ORGANIC ELECTRICITY.
not due to an increased resistance to conduction in the muscle
from its contracted condition is proved by placing the two
corresponding muscles of the same animal, one before the
other, in the same galvanometer circuit, but reversed so that
their currents are opposed to one another, and then tetanising
one of them, for when this is done the current of the other
acquires the ascendant.
The negative deflection in the first form of the experiment
is due, therefore, neither to invasion of the galvanometer
circuit by the exciting current, nor to a change in the direction
of the ordinary current, nor to increased resistance to conduc-
tion. It is the result of the counter-current produced at the
platinum electrodes of the galvanometer during the passage of
the ordinary muscular current ; and this counter-current de-
flects the needle negatively as soon as the ordinary muscular
current begins to lose its influence on it through the annihil-
ating effect of the tetanus. The negative deflection is also in
proportion to the intensity of the ordinary current, and is,
moreover, increased by the negative effect of the parelectro-
nomic layer, which, according to Du Bois Eeymond, is not
affected by the act of contraction.
The diminution or cessation of the ordinary muscular cur-
rent has been employed by Du Bois Eeymond to explain
certain curious experiments which he has latterly made. The
general muscular current of the frog sets, as has been stated,
from the toes to the head of the animal. Now, if one of the
legs of a frog be paralysed by cutting the sciatic plexus, the
feet being then placed in the two conducting vessels for the
electrodes of the galvanometer, and the animal tetanised with
strychnine, it is evident that the ordinary general current will
be diminished in the tetanised limb. Under these circum-
stances, the galvanometer indicates not only an increase of the
upward current in the paralysed limb, but a downward current
in the tetanised one. On the human subject a corresponding
PRESENT STATE OF ORGANIC ELECTRICITY. 331
experiment may be made. The forefinger of each hand being
dipped into the saline solutions along with the electrodes of
the galvanometer, no deflection occurs. But if all the muscles
of one arm be strongly and continuously contracted, a current
is indicated as passing from the finger to the shoulder in the
contracted arm, and in the opposite direction in the relaxed
one. It is evident that this current is the result of the dimi-
nution of the ordinary general muscular current in the con-
tracted arm, and the substitution for it of the closed circuit
of the ordinary current of the opposite arm.*
The Electric Properties of Nerve. The resemblance between
many actions of the nervous system and certain electric phe-
nomena has frequently impressed physiologists ; but investi-
gations of this subject have been so generally mixed up with
that of the electricity of muscle, as to lead to no precise
result. Matteucci had failed in obtaining any indication of
electric currents in nerves ; but, nevertheless, the singular
parallelism between the two powers could not be overlooked ;
and Faraday has pointed out the importance of such considera-
tions in his statements regarding electro-nervous action and
reaction. More recently, Du Bois Eeymond has admitted
that electricity and the nervous force are at least equivalents.
He was the first to derive electric currents from the nerves,
and has procured many most remarkable results from his
researches on the subject.
The Electric Condition of a Nerve in the Intervals of Func-
tional Activity. By employing a very delicate galvanometer,
Du Bois Eeymond has detected the electric current in nerve,
and has determined its laws. They are similar to those of
the muscular current, having the same relation to the longi-
tudinal and transverse sections ; except that as the nerve
presents no natural transverse section, the relative conditions
* The general muscular current and the frog- current are treated of in the
first chapter of section iii. of the Untersuchungen.
332 PRESENT STATE OF ORGANIC ELECTRICITY.
of the longitudinal and transverse sections cannot be detected
before the nervous cord has been cut across. If a transverse
section is in contact with one electrode, and the outer surface
of the nerve with the other, the current passes through the
galvanometer wire from the latter to the former. The current
has the same relative direction whether the transverse section
belong to the peripheral or central extremity of the nerve ;
and, consequently, when a segment of nerve is doubled in the
middle, the current passes from the loop to both sections.
The currents derived from the natural longitudinal section
that is, the outer surface of the segment of a nerve are simi-
lar to those derived from the outer aspect of a muscle ; and
there is reason for believing that if the small size of the
transverse section did not present an obstacle, it also would
be found to be in the same condition of electric tension as a
corresponding surface in a muscle.
It is a remarkable and important fact that no difference
exists in the laws of the electric current in the two classes of
cerebro-spinal nerves. The motor and sensory nerves, the
dorsal and ventral roots of the spinal nerves, and the nerves
of special sense, all present the same electric conditions. It
is also remarkable that the spinal marrow and brain afford
the same results as the nervous cords. The former has its
natural and artificial longitudinal surfaces in a positive electric
condition, and its transverse in a negative. In a brain the
entire surface covered by the pia mater, whatever complication
of form or direction it may assume, being morphologically a
longitudinal surface, is electrically positive in relation to
artificial sections of the organ.
Du Bois Eeymond has discovered a very remarkable con-
dition of a nerve produced by the passage of a continuous
electric current through a portion of it. If a continuous
current be passed along a portion of a separated segment of
nerve, it alters the ordinary electromotor condition of the
PRESENT STATE OF ORGANIC ELECTRICITY. 333
nerve in such a manner as to increase the force of the ordinary
current at that extremity of the segment where they correspond
in direction, and to diminish the ordinary current at the other
extremity where they are opposed. That a new condition of
electric tension is induced by the exciting currents along the
entire segment is proved by the galvanometer, which indicates
a current in the direction of the exciting current between
points equally distant from the middle of the outer surface of
the segment, where no galvanometric indications of the ordi-
nary current can be derived.
From the resemblance which this peculiar condition of a
nerve bears to the change which Faraday supposes to take
place in a wire along which a current is induced by a neigh-
bouring current, Du Bois Eeymond adopts the term applied
by the former to the induced change, and denominates the
new condition of the nerve the electrotonic state.
In the electrotonic state the ordinary electromotor elements
are evidently polarised, so as to have all their positive and
negative poles turned in opposite directions. Du Bois Eey-
mond conceives that the change may be explained by assuming
that the ordinary electromotor elements consist each of two
dipolar molecules, with their positive poles in contact, and
that in the electrotonic condition one of the dipolar molecules
of each electromotor element turns on itself from 90 to 100.*
The Electric Condition of a Nerve during Functional Ac-
tivity. As Du Bois Eeymond was the first to detect the
ordinary electric current in nerves, so we owe to him the only
information we possess regarding the electric condition of a
nerve during functional activity. The question to be deter-
mined is the electric condition of a motor nerve while it is
engaged in transmitting to a muscle the stimulus which
* The greater part of the first division of vol. ii. of the Unterwwhungen
is occupied with the subject of the nerve-current. The statement of the laws
of the nerve-current will be found at pp. 262, 263.
334 PRESENT STATE OF ORGANIC ELECTRICITY.
induces contraction, and of a sensory nerve while it is convey-
ing to the sensorium the impression produced at its peripheral
extremity. In this investigation it was necessary to produce
in the nerve that state of continuous activity which is required
for overcoming the inertia of the needle. Such a condition
may be procured by mechanical or chemical agents, or by the
transmission of interrupted electric currents.
A segment of a nerve having been placed so that its longi-
tudinal and one of its transverse sections are in connection
with the electrodes of the galvanometer, if, after the needle
has come to rest at the angle of deflection produced by the
nerve-current, the other end of the nerve be burned or crushed,
the needle will return towards zero a few degrees.
If the extremity of the nerve of a rheoscopic leg be con-
nected with the galvanometer in a similar manner, and the
leg itself be confined in one limb of a glass syphon, into which
a boiling solution of salt is passed from the opposite limb, the
needle will indicate a similar negative variation.
A frog having been fastened down, its sciatic nerve laid
bare, cut across at the lower end, and turned up from the
thigh, so as to have its longitudinal and transverse sections
applied to the electrodes, the needle will exhibit the usual
positive deflection. If the animal be now tetanised by strych-
nine, the needle will return towards zero, and continue to
oscillate, approaching zero during each spasm, and receding
from it in the intervals of muscular action that is, while the
nerves are not engaged in conveying their stimulus of muscular
contraction.
From these experiments it appears, that when a motor or
sensory nerve is in a state of functional activity, its ordinary
electric condition is altered, as it no longer affords the same
galvanometric indications, the current derived from it being
diminished.
Electricity passed through a nerve excites that condition
PRESENT STATE OF ORGANIC ELECTRICITY. 335
which in a motor cord induces muscular contraction ; and in
a sensory, common or special, sensation. In order, therefore,
to determine the nature of the change which occurs during
the functional phase of a nerve, Du Bois Eeymond had recourse
to electric excitement.
It has already been stated that a nerve is thrown into what
has been called the electrotonic condition as long as a con-
tinuous electric current passes through a portion of it. Now,
as muscular contraction is induced at the closing and opening
of the circuit, and at the movements of variation in the density
of the exciting current, and as sensation also occurs most
vividly under similar conditions, it was necessary to examine
the electrotonic state, as produced by variable or intermitting
currents. For, as a variable or alternating electrotonic state
promised the greatest resemblance to a state of continuous
functional activity, its investigation might be expected to
throw some light on the change which takes place in the
ordinary electric condition of a nerve when it is thrown into
action.
Du Bois Keymond found that the galvanometer as distinctly
indicated positive and negative variations in the currents which
passed through it, when these currents were derived from the
extremities of a segment of nerve which was in an intermit-
ting, as when it was in a continuous, electrotonic state. When,
however, the interruptions of the exciting primary current
become very frequent, the negative variation of the derived
currents becomes more marked, and even the positive varia-
tion, diminishes. It appeared probable; therefore, that by pro-
ducing the electrotonic state of the nerve by rapidly alternat-
ing currents, the negative condition already indicated might
be increased. It was consequently found that if, after the
needle had come to rest in the deflection by the ordinary
nerve-current from either end of the segment, a rapid series of
alternating currents be transmitted through a portion of the
336 PRESENT STATE OF ORGANIC ELECTRICITY.
cord from an induction-coil (in which each primary current
induces an opposite in the other wire), the needle returns to
zero.
These experiments appear to prove that when a nerve is
completely excited or tetanised by electricity, its usual electro-
motor power is diminished or in abeyance ; and as a similar
loss of electromotor power also accompanies intense func-
tional excitement from ordinary agents, Du Bois Eeymond
conceives this negative electric condition to be in some man-
ner related to the motor or sensory functional power of the
nerve.*
To what is the Polarisation of the Nerve, when in a state
of Functional Activity, due ? A nerve is thrown by a current
of electricity into an electric condition apparently similar to
that in which it is during excitation by its normal stimuli.
Is its natural action due, therefore, to electricity? Is its
natural electrotonic condition similar to its so-called artificial
condition ? Is it induced by an electric current ? Du Bois
Reymond's opinions on this subject are guardedly expressed.!
He holds the so-called nervous principle and electricity to be
similar or alike. A nerve in action is in an induced electro-
tonic state ; and exhibits a consequent amount of negative
variation of its ordinary electric current. The source of the
inducing current is not stated ; but its direction may be con-
ceived as resulting, during its influence, from the direction
and extent of the rotation which occurs in one or the other of
the two dipolar molecules, of which the presumed ordinary
peripolar electromotor elements consist, and on which the
ordinary current of the nerve depends. The induced current
* Chap. vii. of the second division of vol. ii. of the Untcrsuchungen.
f See p. xv. of the preface of the Untersuchungen, in which Du Bois
Eeymond states that the electricity in muscle and nerve will probably ulti-
mately prove to be not the mere consequence of their organic processes and
actions, but the actual source of their activity.
PRESENT STATE OF ORGANIC ELECTRICITY. 337
will be more or less directly centrifugal or centripetal as
long as the inducing current or power rotates the peripheral
or the central dipolar molecule in each pair of double elec-
tromotor elements in the series, round an arc of from 90 to
180.
The Electric Relations of Centrifugal and Centripetal
Nerves are identical. It would appear to be an important
result of Du Bois Reymond's electro-physiological researches
that motor and sensory nerves exhibit no difference in their
electrical relations. The electrotonic condition can be in-
duced in either direction. It may consequently be inferred
that a motor nerve is capable of conveying its mere influence
in either direction, but effectively only when it terminates in
a muscle. On the other hand, a sensory nerve is capable of
conveying its impression both ways, but with effect only
when it reaches a sentient centre. In so far as the investiga-
tion has been carried by employing electricity as the exciting
agent, Du Bois Reymond draws the following conclusion
from his experiments : " that in both kinds of nervous fibres
the innervation advances in both directions with equal
facility." *
The Law of the Excitation of Nerves ly the Electrical Cur-
rent. When a uniform current is transmitted through the
nerve of the prepared limb of a frog, the leg contracts only at
the closing and opening of the circuit. In order to keep up
the contraction, or to produce a tetanic condition of the mus-
cles, the current must be variable or intermittent. The action
of a muscle is not, therefore, equivalent to the strength of the
the electric current which may be transmitted along its
nerve, but to the variations in it. The law is thus expressed
by Du Bois Reymond : " It is not the absolute value of the
density of the current in a motor nerve which corresponds to
the contraction of the muscle ; but the variation in this value
* Uhtersuchungen, vol. ii. p. 590.
Z
PRESENT STATE OF ORGANIC ELECTRICITY.
from one moment to another, the excitation being greater the
greater and quicker the variations in a given time." * This
law is also illustrated by the so-called secondary contractions,
which are produced by bringing the nerve of the prepared
frog's limb into contact with a muscle during its contraction.
If the nerve is laid upon a muscle which is in a tetanic condi-
tion, however produced, the muscles of the limb become
tetanised also. This secondary tetanus is the result of that
alternating negative variation which the ordinary muscular
current undergoes during continued contraction.
The nerves of sensation, like those of motion, are more
particularly affected at the closing and opening of the circuit,
and by variations in the current ; but they would also appear
to be capable of excitement by a constant current.^
The organised being may be considered electrically as pre-
senting a system of electrical currents, excited by arrangements
in the system of its fluids, textures, and organs ; the two systems
representing each other. The electric disturbances and currents
in the Microcosm are represented by similar but grander phe-
nomena in the Macrocosm. These phenomena coincide in
both cases with the disposition of component parts, and rank
with other forms of material force alternately as causes and
effects. But the organised being is, moreover, subordinated
to those indwelling psychical powers and impulses by which
it enjoys its prescribed freedom.
The Successive Opinions which have been entertained regard-
ing the Action of the Electric Organ. Walsh concluded that
the electricity of the Torpedo is entirely due to the batteries ;
that their upper and under surfaces are capable, from a state
of electric equilibrium, of being instantly thrown, by a mere
* Untersuchungen, vol. i. p. 258. "f Ibid. p. 283.
I In the report, as originally printed, a description of the special electrical
apparatus in certain fishes is then given ; but, as it is substantially the same
as that related in the preceding paper, it is not considered necessary to repro-
duce it. EDS.
PRESENT STATE OF ORGANIC ELECTRICITY. 339
energy, into a plus and minus state, like that of a charged
phial ; and that the current results from a conducting medium
between their opposite surfaces being supplied naturally or
artificially. Galvani originally, Becquerel subsequently, and
latterly Matteucci, conceived the batteries to be charged by
electricity developed in the brain, or central organ of the ap-
paratus. Eudolphi considered the perpendicular prisms in
Torpedo as galvanic piles, the horizontal series in Gymnotus
as trough arrangements ; but without entering into the details
of the comparison. This view of their action does not explain
the intermittent and voluntary character of the electric dis-
charges. For, as Valentin has stated, the organs in the fish
cannot be complete galvanic batteries, or they would be
continually charged, and a current would follow every suit-
able closure of the circuit. Valentin proposes the follow-
ing theory of the apparatus. He assumes the structure of the
battery to be a series of closed spaces ; the series enveloped in
thicker, the spaces separated by thinner aponeurotic laminae ;
each space being lined by a vascular epithelium, under
which the nervous plexuses lie, and filled with fluid. He
supposes that there results from the organic or nutritive
reactions of the circulating blood, the epithelium, and the
contained fluid of each space, a certain amount of electric
force,, not, however, sufficient to overcome the insulating ob-
stacle opposed to it in the aponeurotic walls ; all the spaces in
the battery are, therefore, so far only insulated electrical
spaces. As soon, however, as the will of the animal deter-
mines a flow of nervous force into the spaces, the organic re-
actions become so much exalted that the resolved electric
force overcomes the insulating power of the laminae, and a
current is produced ; the current being confined to the series
by their thicker aponeurotic walls.* This theory, although it
may account for a sudden increase of electricity in the organ,
* " Electricitat der Thiere " in Wagner's Handworterbuck. .,
340 PRESENT STATE OF ORGANIC ELECTRICITY.
affords no explanation of its progressive character ; the current
is not accounted for.
The theory which most satisfactorily combines the anato-
mico-physiological as well as the electrical phenomena of the
apparatus, is that lately propounded by Professor Pacini of
Florence.* Having discovered the important anatomical fact
that the nerves are distributed on one surface only of the
electrical elements of the battery, while the vessels and nu-
cleated cellular texture occupy the other ; he finds in these
structural peculiarities the condition which is wanting in
Valentin's theory to explain the progression of the electricity.
Pacini refers the electrical batteries in the fish to two forms
of structure, and two modes of action ; of the first and
simplest form, the Torpedo affords the type, of the second and
more complicated, the Gymnotus. The batteries of Malap-
terurus are probably referable to the form in Torpedo, those
of Eaia certainly to that in Gymnotus. In the Torpedo, ac-
cording to Pacini, the action is analogous to that which takes
place in a thermo-electric pile, inasmuch as he conceives it
to depend upon a peculiar dynamical difference in the condi-
tion of the two surfaces of each diaphragm of this binary type
of pile. The nerve-surface and the vasculo-cellular surface
of the electric diaphragm correspond to the bismuth and
copper, or bismuth and antimony elements of a thermo-elec-
tric arrangement ; the nervous influence in the former taking
the place of the heat applied in the latter. There is here
assumed, what on other grounds is highly probable, that the
electrical and nervous forces are correlative ; and here it
must be admitted that in Torpedo, as pointed out by John
Hunter,t the bulk of the nerves in relation to the batteries is
much greater than in Gymnotus, which exemplifies Pacini's
second or ternary type of animal battery. When the Torpedo,
* Sulla struttura intima dell' organo elettrico del gymnoto, e di altri pesci
elettriti, 1852. t Phil. Trans. 1773.
PRESENT STATE OF ORGANIC ELECTRICITY. 341
therefore, wills a shock, or when, through the reflex action
of its electrical nervous centre, a shock is induced, a sudden
and copious nervous influx flows over the under surfaces of
its electric diaphragms, the upper surfaces are thrown into
an opposite electrical condition, and a current is the conse-
quence.
Pacini refers the structure of the battery in Gymnotus to a
ternary type. This type presents a negative element, which
consists of the fibrous layer on which the nerves ramify, to-
gether with the fluid which it bounds below; a positive ele-
ment formed by the ridged vasculo-cellular layer, and the
conducting inter-diaphragmatic fluid. The vasculo-cellular
layer predominating in this ternary type over the nervous,
Pacini conceives the electricity to be evolved in the organic
actions of the vasculo-cellular layer under the influence of the
nerves. In other words, the will of the Gymnotus, or the re-
flex action of its electrical nervous centre, directs an influence
along the nerves of its batteries over the fibro-nervous layer,
which suddenly exciting the nutritive or other organic actions
of the highly-developed vasculo-cellular layer, an electrical
disturbance is produced, with an opposite electrical condition
of the fibro-nervous and vasculo-cellular layers of the dia-
phragms, and consequently a current through the series.
Pacini compares the wide-meshed fibrous layer, on the under
surface of which the nerves ramify, to the hollow cylinder of
porous clay, which in a Bunsen's or a Grove's galvanic ar-
rangement separates the negative from the positive elements.
The Batteries of the Fish are Independent Electromotor
Structures. From the observations of Pacini, the terminations
of the nerves appear to form important elements in the
structure of the battery. On physiological grounds, however,
it appears probable that the peculiar texture of the electric
diaphragm is itself the seat of the electromotor power. As
an ultimate muscular fibre contracts, although entirely sepa-
342 PRESENT STATE OF ORGANIC ELECTRICITY.
rated from the nerve, it remains to be determined whether
an appreciable electric discharge cannot be procured from an
isolated element of the battery. If so, it may be presumed
that the force which in the form of a contraction is elicited
from a muscular fibre by the influence of a motor nerve is re-
placed by electric force when the same kind of nerve influences
an ultimate element of the electric structure. The laws of the
electromotor power of the electric organ cannot be determined
by experiments on its entire mass, or on rudely-separated
portions of it. The parts must be selected and removed on
precise anatomical and physiological principles ; and as Du
Bois Reymond has stated his intention of investigating the
electrical organs of the fish, his previous researches show that
he will be guided in his proceedings by such considerations.
If the battery is separated from its nervous centre by
section of the trunks of all the nerves which supply it, it will
still afford discharges if the nerves are irritated ; and the
different portions of the organ, even the smallest, will do so
likewise if the nerves which are distributed to them be simi-
larly treated. Matteucci, who has latterly admitted that the
nervous centre is not the source of the electricity in the fish,
states that if even a minute fragment of the battery of the
Torpedo is irritated by a spiculum of glass, it will yield a dis-
charge."^
Peculiar Character of the Electricity evolved from the Bat-
teries of the Fish. The nature of the force evolved from the
batteries of the fish is evinced by the shock and spark, by its
influence on the galvanometer, its magnetising and heating
powers, and its chemical action. The absolute quantity of
electricity which the animal can put in circulation at each
effort is enormous. For, as it can decompose water, and form
magnets, it must greatly exceed the quantity which can be
produced by any ordinary electrical machine. It is probable,
* Traitt des Phtnomenes Electro -physiologiques, etc.
PRESENT STATE OF ORGANIC ELECTRICITY. 343
therefore, that the animal has the power of continuing the
evolution for a sensible time ; so that its successive discharges
rather resemble those of a voltaic arrangement intermitting
in its action than those of a Leyden apparatus charged and
discharged many times in succession. At the same time the
power is one of low intensity, so that a dry skin wards it off,
though a moist one conducts it.*
It is remarkable that the electric fishes, although affected
like other animals by ordinary electric shocks, do not appear
to feel the electric discharges which are produced by them-
selves, or by other individuals of the same species.
The Condition of the Water which surrounds the Fish at the
moment of discharge of the Electric Organs. At the moment of
a discharge in water, the currents between the opposite surfaces
of Torpedo, or between the ends of Gymnotus, instead of being
confined to a transverse area of limited extent, as when they
pass along a wire during a discharge in air, must be diffused
through a considerable extent of the water surrounding the
fish. The entire current force of the batteries must, in fact,
be subdivided into numerous subordinate axes of force arranged
in lines which come round the margins of Torpedo from back
to belly, and along the sides of Gymnotus from head to tail.
There is therefore at the moment of discharge an atmosphere
of power around the fish which, in the language employed by
Mr. Faraday in reference to the magnetic force, may be con-
sidered as disposed in sphondyloids determined by the lines,
or rather shells, of force. " The magnet, with its surrounding
sphondyloid of power, may be considered as analogous in its
condition to a voltaic battery immersed in water or any other
electrolyte, or to a Gymnotus or Torpedo at the moment when
these creatures, at their own will, fill the surrounding fluid
with lines of electric force." It is evident, therefore, that
another fish, placed so that its antero-posterior axis is in the
* Faraday, Researches in Electricity, vol. i. p. 101.
344 PRESENT STATE OF ORGANIC ELECTRICITY.
direction of lines of inductive action in the water, will be
affected less powerfully by the circulating electric power than
if it were placed across these lines. Mr. Faraday * found that
while the Gymnotus can stun and kill fishes which are in
various positions in relation to its own body, it can, moreover,
by throwing itself so as to form a coil enclosing the fish, the
latter representing a diameter across it, 'so concentrate its
currents of one side as to strike it motionless as if by lightning.
The Torpedo would also appear, from the observations of Dr.
Davy, instinctively to elevate or arrange its margin so as to
adjust the direction of its currents to the position of the object
through which it wishes to pass them. " Thus," as Mr. Faraday
observes, "the very conducting power which the water has,
that which it gives to the moistened skin of the fish or animal
to be struck, the extent of surface by which the fish and water
conducting the charge to it are in contact, all conduce to
favour and increase the shock upon the doomed animal."
* Phil. Trans. 1839.
CONFERVA ON THE SKIN OF THE GOLD-FISH. 345
XVII. ON THE CONFEBVA WHICH VEGETATES
ON THE SKIN OF THE GOLD-FISH.*
LADY BRISBANE having observed that a gold-fish which had
lived for some time in a glass vase presented a very unusual
appearance, as if a quantity of cotton were attached to its
dorsal fin and tail, requested Mr. Bryson to explain the cir-
cumstance. That gentleman, having seen in the Microscopic
Journal a notice of the occurrence of vegetables parasitic on
living animals,t at once suspected that the cotton-like substance
was a plant. Lady Brisbane kindly allowed him to remove
the fish to Edinburgh for more accurate examination. Mr.
Bryson sent it to me, with the information that the peculiar
substance had made its appearance on the animal six weeks
before.
The fish had been conveyed to town in a jug of water,
but had died on the journey, so that I lost the opportunity
of observing the parasite during the life of the animal.
The water had begun to be tinged with blood and colouring
matter from incipient putrefaction. The results of the
examination were not, therefore, so satisfactory as I could
have wished.
The parasite, when examined under water, presented to
the naked eye a continuous mass consisting of minute filaments
about three-quarters of an inch in length and extending all
along the dorsal and posterior edge of the tail-fins. The
* Bead before the Botanical Society of Edinburgh, January 13, 1842.
t See Ann. and Mag. Nat. Hist. vol. viii. p. 229, and p. 10.
346 CONFERVA ON THE SKIN OF THE GOLD-FISH.
filaments, although individually transparent, were so close to
one another and so numerous that the mass appeared opaque.
When the lateral portions of the mass were separated along
the median line, so as to display the free edges of the fins,
these edges were observed to be shrivelled, not, as appeared
to me, by a process of ulceration, but by an irregular inter-
stitial absorption. This absorption was more evident along
the bounding edge of the parasitic mass, where it presented
the appearance of a furrow, in which 4he parasite grew with
more luxuriance than elsewhere.
What was the exact state of the surface to which the
parasite adhered I am not prepared to say. I could detect no
substance corresponding to the false membrane described by
certain observers as constituting the soil on which vegetate
those parasites which infest the air-cells of birds ; neither
could I satisfy myself that the substance which formed the
infested surface was merely the mucous covering of the fish.
I am inclined, however, to lean to the latter opinion, for two
reasons first, because the surface exhibited the pigment cells
of the skin ; and secondly, because I detected solitary indivi-
duals attached to the broad scales of the back.
Each plant consists of a jointed filament, in some indivi-
duals single, in others dividing dichotomously towards the
attached extremity, but more frequently near the summit.
The filament tapers gradually from the base to the summit.
The former is very slightly dilated, rounded and closed at the
extremity, which is destitute of appendages. The latter varies
in different individuals under different circumstances, as will
be afterwards described. The articulations are elongated,
varying in length from ten to fifty times their breadth. Basal
articulations were met with, having a breadth of the 800th of
an inch ; acute or barren terminal articulations were about the
2000th of an inch. The length of the articulations increased
towards the summit, the basal being in general the snortest.
CONFERVA ON THE SKIN OF THE GOLD-FISH. 34*7
Each articulation was tubular, filled with a transparent fluid
in which floated granules. Their walls appeared to be homo-
geneous ; I could detect no double membrane, but at the spot
where the neighbouring articulations were connected, the
internal surface of each appeared to leave the external surface
of the filament so as to form by conjunction the flat dia-
phragms. It would appear, then, that the walls of the cells
are originally double, but have coalesced in the progress of
growth. Towards the basal extremity of each articulation,
generally close upon it, but sometimes a little removed, is a
globular transparent vesicle. This vesicle varied in size,
directly as the diameter of the articulation. I did not observe
this vesicle in any instance exhibiting a nucleus or granular
contents. I occasionally observed it floating free in the fluid
of the articulation ; but this might have been the effect of
violence. The fluid of certain of the articulations contained
granules about the 5000th or 6000th of an inch. Others again
contained no granular matter. These granules did not exhibit
molecular motion. I, on more than one occasion, observed a
steady onward motion of the granules and transparent vesicle ;
but this appeared to depend on unequal pressure and level of
the object-plates.
From certain spots on the external surface of the articula-
tions spots which appeared to be arranged in no appreciable
order, there sprung bundles of very numerous, cylindrical,
elongated, and transparent filaments. These were so nume-
rous and so convoluted and twisted as to defy every attempt
to disentangle them ; in fact, they occasionally obscured alto-
gether the stems or primary filaments of the plant. They
arose from all the articulations except the basal and terminal,
at least I never saw them springing from the latter, although
I occasionally saw them arising from what I took to be the
upper end of a basal articulation. They were quite cylin-
drical, as thick at their free as at their attached extremities,
348 CONFERVA ON THE SKIN OF THE GOLD-FISH.
and about 40 1 00 th of an inch in diameter. In structure they
were homogeneous, apparently gelatinous, and covered with a
fine membrane.
This parasite propagates by spores formed in its terminal
articulations, which are developed into spore-cases for that
purpose. Having observed terminal articulations in all stages
of development, I may state the changes they undergo to be
the following :
1. A perfectly barren terminal articulation is elongated,
spear-shaped, transparent, without granules.
2. A terminal articulation which is destined to become a
spore-case does not elongate so much, and is from the first,
or at least from an early period of its growth, full of granules,
which give it a grey colour. It is also elongated, fusiform, and
connected to the penultimate articulation by a narrow neck.
3. It becomes more distinctly fusiform, retaining its other
characters.
4 The granules appear here and there to increase in size,
or at least larger granules appear diffused through the mass.
These larger granules or vesicles are more or less transparent.
The articulation now becomes cylindrical, with rounded ex-
tremities and a constricted neck.
5. The articulation increasing in dimensions, but retaining
the same shape, contains a packed mass of perfectly trans-
parent globules, which are uncompressed and without appre-
ciable internal structure.
6. The fertile articulation or spore-case bursts ; that is, I
have seen it with its contents hanging together from a rup-
ture in its walls.
Proceeding to observe the changes which the spore itself
undergoes, I detected lying here and there, among the attached
extremities of the primary filaments, groups of spores corre-
sponding in numbers and characters to those which I had
seen escaping from the spore-cases.
CONFERVA ON THE SKIN OF THE GOLD-FISH. 349
The most careful examination revealed no nuclei or con-
tents of any kind in these transparent vesicles, which in this
their perfect state were about Ywo-th of an inch in diameter.
The first step in the development was an opacity in the
spore, due to the development of granules similar to those
which have been so often mentioned.
2. The vessel elongates.
3. It appears double ; that is, two-celled.
4. Both cells elongate and acquire additional cells at the
extremity, which is known to be the terminal extremity by
secondary filaments appearing on it.
A sufficient number of examples could not be met with to
trace these changes with greater minuteness, so that certain
circumstances which I was anxious to detect, and to which I
shall allude immediately, escaped observation.
I may state that I met with one example of the incipient
development of a dichotomous primary filament. It occurred
at the point of attachment of a fertile articulation, and might
therefore be considered, in some measure, as one mode in
which the primary filament or axis of the individual is con-
tinued, when its elongation would otherwise have been inter-
rupted by the development of the formal terminal articulation
into a spore-case.
This incipient lateral filament appeared as a conical projec-
tion from the side of the upper extremity of the penultimate
articulation. I could not make out the existence of a dia-
phragm at the base of the little cone ; as however it, as well
as the penultimate articulation, was full of granular matter, a
diaphragm might have existed, although I did not observe it.
A clear vesicle, such as I have formerly described, was situated
at the terminal extremity of the penultimate articulation ; but
whether it belonged to the new articulation or to the old one,
I could not determine.
I have been unable to determine, in a satisfactory manner
350 CONFERVA ON THE SKIN OF THE GOLD-FISH.
the exact nature of the clear vesicle which is found in each of
the articulations. It may be the nucleus of the original cell
of the articulation ; but if it be so, it must be considered as a
barren nucleus ; having increased in size proportional to its
cell, having lost the normal appearance of a nucleus, and
having never performed the function of one. May it not, with
greater propriety, be considered as some form of the endo-
chrome, a result of development of the granules of the articu-
lation ? It exactly resembles the spores of the terminal articu-
lations, which, as has been already stated, originate in the
granular endochrome of this articulation.
The parasitic plant I have now described resembles in many
respects those found by Hannover and Stilling on the newt
and frog. As in these, the filaments swarmed with infusorial
animalcules, Monads, Bursarice, etc. Some of these doubtless
lived among the filaments while the fish was still alive ; others,
again, as the Bursarice, must have taken up their residence
there after the commencement of putrefaction. Hannover, in
Muller's Archiv, 1842, page 73, has described the develop-
ment of the conferva of the frog and newt, and has mentioned
the animal-like movements of the spores. Mr. Daniel Cooper
(Microscopic Journal) has frequently observed a cotton-like
conferva on the gills and fins of gold-fish. From a preserved
specimen, an examination of which was afforded me by Pro-
fessor Balfour, I am inclined to believe in the existence of
more than one species of this genus of parasitic Algae.
CASE OF SARCINA VENTRICULI. 351
XVIIL HISTOEY OF A CASE IN WHICH A FLUID
PEKIODICALLY EJECTED] FEOM; THE STOMACH
CONTAINED VEGETABLE OEGANISMS (SAE-
CINA YENTEICULI) OF AN UNDESCEIBED
FOEM.
MR. , aged 19, consulted me about a stomach-complaint,
under which he had been labouring for four months, and
which had more or less resisted every attempt made for its
removal He informed me that he considered it to be water-
brash ; that it attacked him on awakening in the morning
with a feeling of distension of the stomach ; that, without
any effort of vomiting, a quantity of fluid, varying in volume
from, two-thirds to a whole wash-hand basinful, passed up
from his stomach ; that after this he was quite relieved, and
experienced no further inconvenience till . the evening of the
same day, when, without decided distension, sounds as of a
fluid boiling or bubbling, and proceeding from the region of
his stomach, were perceptible to himself and to those around
him ; that he slept well enough, but was generally attacked
in the usual manner next morning. Such was my patient's
own account of his case.
On examining more particularly into the symptoms, I
could ascertain nothing positive. His tongue and pulse were
natural ; he had no headache, nausea, or thirst ; no tumour
could be detected in the epigastrium, and no pain on pressure
was complained of in the region of the stomach. The bowels
were moved daily, and the stools were normal. His appetite
352 CASE OF SARCINA VENTRICULI.
was not affected, and the usual articles of diet appeared to
agree with him. He was thin, but had a good complexion,
and his flesh was firm. He stated that he had formerly been
very fat, but that this had left him before the accession of
his stomach-complaint. I was informed that one of his
testicles had never descended beyond the groin.
Of the various remedies which had been tried for his
relief, prussic acid appeared upon the whole to have
exercised the greatest influence over the disease, preventing
the attacks with considerable certainty for several days in
succession.
Being unable to make up my mind as to the exact nature
of the case, but conceiving it probable that there might be
ulceration or some other organic lesion of the stomach, I
ordered croton-oil, frictions of the epigastric region, and the
internal remedies to be discontinued. I also requested that
the ejected fluid might be preserved for my inspection.
Next day I found that he had had an attack in the morn-
ing as usual. No new symptoms presented themselves.
On examining the ejected fluid, I was struck with the
truth of what had been stated to me, that it smelt like fer-
menting worts, with a faint acid odour. It appeared, after
having stood for a few hours, moderately transparent and of a
light brown colour. It had deposited in the bottom of the
basin a quantity of a ropy matter, of a granular appearance ;
and on the surface was a mass of froth like the head of a pot
of porter.
By a consideration of all the circumstances of the case, I
was now induced to conceive it possible that this and other
cases of similar stomach-complaints might depend on fermenta-
tion of the contents of the organ. Such a fermentation might,
I presumed, be primary that is, induced by the chemical con-
stitution and relative conditions of the contents of the stomach ;
or it might be secondary that is, induced by circumstances in
CASE OF SAECINA VENTEICULI. 353
the condition of the organ standing in the relations of primary
causes of the whole complaint. But, whatever might be
supposed to be the cause of the presumed fermentation, it ap-
peared to me highly probable that, if it had really taken place,
it would be indicated by the remains of ferment-vegetables in
the ejected fluid.
In the meantime, till I had examined the fluid more
minutely, I merely regulated my patient's diet. Animal food
was recommended ; vegetables and malt liquors were for-
bidden, and a little brandy was ordered in water for drink.
I now proceeded to examine the fluid ejected from the
stomach, and in proceeding to do so, I expected, if I found
any vegetable form at all, to see some of the globular or
moniliform algae, which it now appears pretty certain are
concomitants of certain of the fermentations. What was my
astonishment, then, to find, in the first drop I examined, not
the vegetables I was led to expect, but numerous individuals
of a form, with allies of which the zoologist is familiar ! Drop
after drop exhibited the same specific form, with a precision
which convinced me that I had now to deal with an organism
which, whether animal or vegetable, was closely allied to
certain genera of BACCILLARI^E, and much more closely to the
genus GONIUM among the VOLVOCIN.E.
Before I proceed with the history of the case, or with the
description of the organism which characterised it, it may be
well to state that, in addition to a few fragments and shreds
of undigested food, the ejected fluid presented the following
microscopic elements :
1st. Fecula-cells, globular, ovoidal, and kidney-shaped,
with well-marked hila of attachment. Some of these cells
were transparent and empty, others were full of starch-granules,
and reacted powerfully with iodine. These cells were at first
presumed, and were afterwards proved by comparison, to be
nothing more than the remains of wheaten bread.
2 A
354 CASE OF SAECINA VENTRICUL1.
2d. Much larger, more irregular, flaccid, ruptured, or half-
emptied cells, full of granular matter, which reacted with
iodine, and were recognised as fecula-cells of the potato, as
they appear after boiling.
3d. Minute shreds of muscular fibre, cellular tissue, and
fat-cells, remains of the food.
4^, Globules or globular masses, from 500 to 100 of an
inch in diameter, apparently oily, and presumed, although as to
this no inquiries were instituted, to be some form of the chyme.
5th. Occasionally, but rarely, portions of bran, consisting
of the perisperm of the wheat, recognisable by its internal
surface presenting irregular-sized, ovoidal or hexagonal shallow
fovese, with included fecula-cells.
6tk. The organisms themselves, which I at once recognised
as belonging to the vegetable kingdom, and considered either
as the cause of the symptoms in my patient's case, or at least
as very remarkable and important concomitants.
I may state that these organisms could not have been
swallowed in the water used for drink, as the water employed
by the family for that purpose was regularly passed through a
stone filter. I used every precaution also in ascertaining that
they could not have been introduced along with any article of
diet, and in satisfying myself that they were not portions of
any animal or vegetable tissue.
I now recommended a return to the use of the prussic acid.
I ascertained that it exercised a decided influence over the
disease. After some time, however, I became satisfied that it
acted more by enabling the stomach to retain its contents, than
by any direct influence in preventing the formation of the
fluid itself.
The case proceeded for about a fortnight without any
change in the symptoms, the prussic acid being regularly taken
at bed-time, with the effect of putting off the attacks occa-
sionally for a day or two at a time.
CASE OF SARCINA VENTRICULI. 355
I now determined to give creosote, from a belief that it
would not only act, as the prussic acid had done, in preventing
the ejection of the fluid, but that it would also put a stop to
its formation. This I conceived it would do, whether the
disease arose from a simple fermentation of the contents of
the stomach, or from the development of the organisms as a
primary cause.
A drop of creosote was ordered every night at bed-time.
Supper was forbidden ; a very light dinner of animal food
was recommended, and breakfast indicated as the principal
meal. Cessation of his somewhat sedentary habits, active
country exercise on foot and horseback, and attention to the
bowels were insisted upon.
A decided improvement now took place. The attacks,
instead of recurring almost every morning, now took place
only on the fifth or sixth morning, and latterly at intervals of
eight or ten days. The fluid ejected also diminished in quan-
tity, not exceeding six or eight ounces.
The attacks again increased slightly in frequency, and in
quantity of fluid ejected, but this was at once controlled by a
gradual increase of the dose to four drops at bed-time. It
also appeared advisable to divide the dose, so as to take two
drops in the forenoon and three or four about one hour and
a4ialf after dinner, so as to stop the formation of the fluid.
This effect my patient felt satisfied the creosote produced, as
the bubbling or crackling sensation in the stomach usually
ceased after taking his dose.
The bowels were now acted upon rather smartly, so as to
promote the action downwards from the stomach.
At the present date I have it not in my power to state
that the complaint is removed, although the attacks are much
less frequent, and the quantity of fluid diminished. The
creosote, however, has a most decided control over it, and will,
I am inclined to believe, ultimately cure it. The disease,
356 CASE OF SARCINA VENTKICULI.
indeed, may depend on the patient's time of life, and on the
peculiarity of his constitution, and may gradually disappear
even without medicine, as a consequence of increased cor-
poreal vigour.
The Structure, Mode of Reproduction, and Development of
Sarcina ventriculi, the Parasite detected in the ejected Fluid.
The following description is drawn up from examination of
the ejected fluid for a period of nearly two months.
In every instance the organisms presented themselves in
the form of square or slightly oblong plates. The thickness of
an individual was about one-eighth of the length of one of its
sides. Under a moderate power the sides and angles appeared
straight and well-defined ; but under deeper glasses, the
angles were rounded, and the sides sinuous ; appearances
which resulted from the uncompressed forms of the compo-
nent cells in their particular directions. The flat surfaces
were divided into four secondary squares by two rectilinear
transparent spaces, which, passing from side to side, inter-
sected one another in the centre like two cross garden-walks.
Each of the four secondary squares was again divided by
similarly arranged, but more feebly developed spaces, into the
four ternary squares.
The sixteen ternary squares thus constituted, when ex-
amined with deeper powers, were seen to consist each of four
cells, which were not separated by transparent spaces, but
simply by dissepiments formed by the conjunction of the
walls of contiguous cells.
These sixty-four cells of which the organism consisted did
not present in perfect individuals distinct nuclei ; although
in certain instances appearances presented themselves, having
relation to the reproduction of the organism, and falling to be
described in another part of the paper.
The individual organisms were transparent and slightly
CASE OF SARCINA VENTRICULI. 357
yellow or brown. When carefully examined under favourable
circumstances the cell- walls appeared rigid, and could be
perceived passing from one flat surface to the other as dis-
sepiments. These dissepiments, as well as the transparent
spaces, were from compression of contiguity rectilinear, and
all the angles right angles ; but the bounding cells bulged
somewhat irregularly on the edges of the organism, by reason
of the freedom from pressure.
These circumstances gave the whole organism the appear-
ance of a wool-pack, or of a soft bundle bound with cord,
crossing it four times at right angles and at equal distances.
From these very striking peculiarities of form, I propose
for it the generic term SARCINA.**
Perfect individual SAUCING, of the species now under
consideration, vary from 800 to 1000 of an inch linear
along each of their sides. They are, as has been stated,
slightly brown or yellow under a high power under moderate
glasses they appear dark, and are defined with difficulty on
account of the frequent reflections of the light by the dis-
sepiments. Iodine does not react with them, as with starch,
but tinges them deep brown or yellow. They shrivel but
slightly in alcohol. In nitric acid, even after boiling for some
time, the sixteen ternary squares retain their relative
position, but diminished and shrivelled, appearing like minute
crystalline granules arranged in a square. So persistent are
those arrangements of granules in boiling nitric acid, that I
at one time suspected the existence of silicious loricae, or
isolated raphides, but as I could not detect the same forms or
arrangements in the ashes of the evaporated and calcined fluid,
I do not now believe in their existence.
This species of SARCINA, therefore, consists of sixteen four-
celled frustules, imbedded in a square tablet of a transparent
SARCINULA would have been more appropriate, had not Lamarck already
applied the term to a genus of polyps.
358 CASE OF SARCINA VENTRICULI.
texture, as in the GONIUMS. The four-celled frustules corre-
spond to the cells or globules ; the tablet to the phycomater or
gelatinous matrix of certain of the ULVACE^E.
The generation of SAECINA is fissiparous, each individual
dividing into four. This is proved by the following circum-
stances :
1st. Specimens are frequently met with, which, instead of
16 ternary squares and 64 ultimate cells, exhibit 64 ternary
squares and 256 ultimate cells. Such specimens are not, I
conceive, to be considered as individuals, in as much as 1.
Their four component squares are very loosely connected to-
gether. 2. One or two of the squares may be wanting, or
two or more of these may remain attached by the angles an
arrangement never represented in the primary squares them-
selves.
2d. Large specimens are occasionally met with, which
have most of the characters of composite individuals that is,
of individuals about to divide into four. Such specimens do
not present 256, but only 64 ultimate cells, and these, ex-
hibiting appearances not easily defined, but apparently con-
sisting of four opaque spots, as if each cell were about to be
divided into four parts, or were in the act of producing within
itself four new cells.
Such appearances rendered it difficult to say whether
certain specimens were simple individuals or composite single
adults, or adults about to divide each into four young ones.
I therefore conclude that a perfect individual SARCINA
consists of 64 ultimate cells, but that as soon as each of these
again divides into or produces four new cells, the individual
becomes composite, and may forthwith divide into four young
ones, each of these again to undergo the same quaternary
division.
Such a mode of generation will account for what I fre-
quently observed two, three, or four SAUCING attached by
CASE OF SARCINA VENTRICULI. 359
their angles only, as in the baccillarian genera. It also
explains why I could never detect more than four so united.
It may account for the circumstance that the SARCIK& were
found grouped as it were in colonies, in certain portions of
the ropy fluid, some drops containing numbers of them, others
none at all.
Such is the structure, mode of reproduction and of de-
velopment, of this species of SARCINA.
In tracing these out, it cannot but have been observed how
beautiful is the symmetry of all the arrangements how the
parts of the individual are arranged in the square how these
parts increase in numbers in a geometrical progression 1, 4,
16, 64, 256, and lastly, how the species propagates according
to the same law, 4 in the first generation, 16 in the second,
64 in the third, 256 in the fourth, 1024 in the fifth, and so on
with a rapidity peculiar to such a series of numbers.
Is SARCINA an animal or a vegetable? is it one of the
infusorial Polygastrica, or a minute Alga ? In order to give
a satisfactory answer to this question, it becomes necessary to
analyse the groups to which SARCINA is most closely allied.
Putting out of view for the present the FRAGILLARLE, DIA-
TOMACLE, and other gonioid organisms, the animal or vegetable
nature of which is yet a matter of doubt, I shall proceed to
Miiller's genus GONIUM, the genus of all others to which
SARCINA has the greatest affinity.
The genus GONIUM consists of composite polygastric ani-
malcules, each corpuscle of the whole animal having, according
to Ehrenberg, the organisation of a monad, oral appendages,
visceral sacs, etc. Ehrenberg does not enumerate eye-points
among the characters of the family to which the GONIUMS
belong (VOLVOCIN.E). Without coming to any decision as to
whether the red points on certain species of GONIUM be really
eye-points, or merely optical illusions,* I may state at once,
* It may be well to state, that the red dots do not appear in all the species,
3GO CASE OF SARCINA VENTRICULI.
that I am much inclined to believe that the genus GONIUM, as
at present constituted, contains both animal and vegetable
species the former characterised by oral appendages, volun-
tary motions (eye-points ?), the latter by their simple cellulo-
globular formation. GoNiUM PECTORALE (Pectoralina hebraica,
B. St. Vincent), GONIUM PUNCTATUM, contrary to the opinion
of Bory St. Vincent and others, appear to be true composite
animals.
But Ehrenberg has here, as in many other instances, de-
cided for the animal nature of organisms in which even his
experienced eye could not detect the characters of the family.
Such is the case with GONIUM HYALINUM, GONIUM GLAU-
CUM, and probably with GONIUM TRANQUILLUM.
These three species appear to consist merely of cells full
of chlorophylle imbedded in the square plate which corre-
sponds to the outer envelope of the NOSTOCHIN/E.
To such forms belongs SARCINA. It exhibits no mouths,
no oral appendages, no visceral sacs, and its cells, instead of
having the gelatinous appearance so familiar to the observer
of the animal infusorials, are clear, transparent as if empty,
and have that consistency of wall characteristic of vegetable
structure.
Believing SARCINA to be a vegetable, I may state, in refer-
ence to its characters, that they are of a kind which distinguish
it from all the gonioid plants at present known. It differs
most essentially from PECTORALINA HEBRAICA of Bory St.
Vincent, which, as we have already stated, appears to be a
true animal. It makes the nearest approach to GONIUM
HYALINUM, which with GONIUM GLAUCUM and GONIUM TRAN-
QUILLUM, even Ehrenberg himself seems inclined to hand
over to the botanists under the generic term GONIDIUM.
The generic characters of SARCINA are to be found in the
and it is interesting to observe, that those species in which they have not been
detected are the very species in which oral appendages apparently do not exist.
CASE OF SAECINA VENTEICULI. 361
predominance of the constituent cells over the outer coat or
lorica, in each frustule being four-celled, and in the entire
freedom of these from all coloured contents. Of the specific
characters of a single species much cannot be said.
I define the genus thus :
SAECINA. Plants coriaceous, transparent, consisting of six-
teen or sixty-four four-celled square frustules, arranged
parallel to one another in a square transparent matrix.
Species 1. SAECINA VENTEICULI, miUi. PL xi. Fig. 13.
Frustules 16 ; colour light brown ; transparent matrix
very perceptible between the frustules, less so around
the edges ; size 800 to 1000 inch. Hab. the human
stomach.
As soon as I had detected the SAECINA, I called upon my
friend Dr. George Wilson for an analysis of the fluid. The
following is his report :
tl The liquid sent me for examination was thick and viscid ;
by standing, it deposited a large quantity of ropy matter mixed
with portions of undigested food, and when filtered through
paper it had a pale brownish-yellow colour, and was quite
transparent. It still contained much animal matter in
solution, becoming opaque and flocculent when boiled, and
giving a very copious precipitate with infusion of galls. It
also precipitated nitrate of silver densely, and when evaporated
to dryness, and exposed to a full red heat in a platina crucible,
left an ash containing much chloride of sodium. It had a pecu-
liar acid odour, which all who have observed compare to that
of sour beer ; it reddened litmus powerfully, and effervesced
sharply with alkaline carbonates. These remarks, and all that
follow, apply without exception to portions of liquid ejected
at various intervals during a period of four weeks.
" To determine the nature of the acid which existed so
abundantly in the ejected matter, a pint of the filtered liquid
was distilled in a retort, till nine-tenths of the whole had
362 CASE OF SARCINA VENTRICULI.
passed over. The fluid in the receiver was colourless but
opalescent, and a flocculent matter was diffused through it ;
it reddened litmus strongly, and gave, with nitrate of silver, a
precipitate insoluble in nitric acid, and soluble in ammonia.
The latter reaction seemed to point to the acid as the hydro-
chloric, but as the liquid had not the odour of that acid, and
the presence of flocculent matter showed that substances not
truly volatile, had been passing over with the vapour during
distillation, I suspected that the precipitation of the silver
salt had resulted from chloride of sodium transferred from
the liquid in the retort by a similar process of mere mechani-
cal convection. To decide this point, a portion of the distilled
fluid was evaporated to dryness in a porcelain capsule, and
strongly heated ; distilled water poured upon the residue
precipitated nitrate of silver, indicating the presence of some
fixed metallic chloride.* To remove this, the liquid was
filtered from the animal matter it held in suspension, and
slowly distilled a second time in a capacious retort. The pro-
duct of this distillation was colourless and transparent, and
possessed a strong acid reaction, but gave not the slightest
haze with nitrate of silver. It retained the vomit-smell, and
along with it a faint acid odour, which was not perceptible to
myself, but which others recognised, and pronounced to be
that of vinegar.
* Berzelius has particularly pointed out the difficulty of distilling viscid
animal fluids in retorts, without the transference of non-volatile matters, which
appear to be projected upwards by the bursting of the bubbles of vapour pro-
duced during tumultuous ebullition. Traite de Chimie, tome vii. p. 616,
Ed. 1832.
Liebig has likewise called the attention of chemists to the remarkable power
which vapours possess, of carrying along with them portions of bodies (such
as nitre, boracic acid, chloride of sodium), which in their solid form resist dis-
sipation by very high temperatures. "When such bodies are dissolved in
water, its vapour, even when far below the boiling point, determines their
volatilisation along with itself. Organic Chemistry in its Application to Agri-
culture, 1st Ed. p. 111.
CASE OF SARCINA VENTKICULI. 363
" To ascertain the nature of the acid, six ounces of the
twice-distilled liquid were neutralised with lime-water and
evaporated to dryness. The lime-salt was then transferred to
a tube-retort, and distilled with sulphuric acid slightly diluted.
A colourless liquid collected in the receiver, which was at
once recognised, by its odour, to contain acetic acid. This
experiment was very carefully repeated with four portions of
liquid distilled from different specimens of the ejected matter ;
the result was the same with all, an acid liquid was procured,
which all who smelt it pronounced to be acetic acid.
" I was the more careful in repeating these trials, that
Berzelius has shown that in the analysis of animal fluids,
other volatile odorous acids may readily be mistaken for
acetic acid. He particularly notices that lactic acid, accom-
panied by a chloride, may seem to be an acetate, when
moistened with sulphuric acid ; the sharp smell of the
evolved hydrochloric acid passing for the peculiar odour of
the acetic. Even so expert a chemist as Leopold Gmelin has
been deceived in this way.* But the liquid from the stomach,
the lime-water, and the sulphuric acid, were all tested and
found to contain no chloride, nor did the distilled liquid con-
tain any ; moreover, the evidence of the acid being the acetic,
did not depend on the perception for a moment of a faint and
fleeting odour, when the salt was moistened with sulphuric
acid ; a drachm of liquid was obtained by each distillation, so
that the odour could be perceived and identified by many
persons. In further trial of the acid, it was ascertained, that
when digested in the cold on recently-precipitated oxide of
lead, it formed a soluble salt, having a sugary taste, and pos-
sessing an alkaline reaction. The acquirement of the latter
property, depending on the formation of a subsalt of lead, has
been shown by Liebig to be distinctive of acetic acid.f
* Berzelius, Op. et. loc. citat.
t Graham's Elements of Chemistry, p. 785.
364 CASE OF SARCINA VENTRICULI.
" The proportion of acetic acid in the twice-distilled fluid
was ascertained in the usual way with the alkalimeter, by
finding the quantity of carbonate of potass required to
neutralise it. It was found by several trials, that, on an
average, an ounce of the liquid neutralised 0'4 gr. of the
carbonate ; a quart (32 oz.) would therefore neutralise 12*8
gr. which correspond to 9 gr. of the hydrated (crystallisable)
acetic acid HO + C 4 Hs Ck
" The liquid remaining in, the retort after the first distilla-
tion was now examined and found still to be strongly acid.
This property was traced in part to the presence of a small
portion of free hydrochloric acid. The large amount of
chloride of sodium which accompanied it made it difficult of
detection ; nor did I succeed in ascertaining its proportion.
But I satisfied myself that it occurred only in small quantity
by the following experiments : Some ounces of the filtered
liquid, along with a portion of red oxide of lead, were placed
in a flask provided with a bent tube dipping into a wine-
glass, containing a very weak infusion of blue cabbage. The
flask was then heated till the liquid boiled, and, by the
quantity of vapour sent through the infusion, made the latter
boil also. The cabbage was reddened, but not perceptibly
weakened in tint ; whereas, had free hydrochloric acid been
present in any quantity, it must have been deprived of
hydrogen by the metallic oxide and chlorine evolved. When
the experiment was repeated, with the addition to the flask of
a little sulphuric acid, the infusion was bleached in a few
seconds. A similar experiment was made with the substitu-
tion of a solution of hydro-sulphuret of ammonia for the
vegetable infusion, .with a view to convert any evolved
chlorine into muriate of ammonia. The hydro-sulphuret w r as
then evaporated to dryness, and nitrate of silver added ; a
precipitate of sulphuret and chloride of silver fell, but when
the latter was dissolved out by ammonia, its amount was
CASE OF SARCINA VENTRICULI. 365
found to be very small. Again, several ounces of the liquid
from the stomach were boiled for some time with peroxide of
manganese, and thereafter filtered. The filtered liquid was
then tested for chloride of manganese, with caustic potash ; a
very slight precipitate of protoxide fell. As the quantity of
hydrochloric acid discovered in this portion of the liquid was
too small to explain its marked acidity, I made careful search
for another acid, and soon detected the presence of one which
was not volatile, but was destructible at high temperatures.
Different processes were adopted for the isolation and purifi-
cation of this acid, which was separated with much difficulty
from the accompanying salts and animal matter. I state the
results very briefly.
" The concentrated liquid from the retort, which now pos-
sessed a dark-brown colour and was very viscid, was evapo-
rated on the water-bath till it ceased to lose weight. It
formed a gummy mass,' which remained moist after many
hours' exposure to a heat of 212, and retained unimpaired
the power of reddening litmus strongly. The mass was boiled
with successive portions of alcohol of sp. gr. O880, so long as
the latter acquired an acid reaction ; the greater part of the
animal matter remained undissolved, but the alcohol was
coloured dark-brown. On evaporating this solution on the
water-bath, a viscid matter was left, strongly acid to litmus,
and possessing a saline taste occasioned by the chloride of
sodium dissolved along with it. The alcoholic extract was
boiled with successive portions of sulphuric ether, recently
rectified from carbonate of potass, and ascertained to be quite
neutral. By this treatment the extract lost its acidity, which
was transferred to the ether ; but it required a large quantity
of the latter to remove it entirely. The etherial solution was
of a pale-yellow colour, and had dissolved very little of the
salts or animal matter. When the ether was vaporised on
the water-bath, there remained a thick yellow liquid, redden-
366 CASE OF SARCINA VENTRICULI.
ing litmus strongly. It was kept for an hour at the tempera-
ture of 212 without drying up ; it could be dissolved in
water and evaporated to its original consistence many times
in succession, without dissipation of the acid ; but when left
in its most concentrated state, it absorbed moisture from the
air, and became more liquid. When exposed in a capsule to
a naked flame, it darkened in colour, the animal matter
became charred, and the whole was destroyed.
" Leopold Gmelin and others have shown that when hydro-
chloric acid is accompanied by much animal matter, it may be
entangled in it, so as to escape dissipation by heat. It will
afterwards be shown that the acid was certainly not the
hydrochloric ; but to obviate any objection which might be
founded on this fact, several portions of the liquid were treated
in the following way : Some ounces were concentrated by
evaporation, and boiled on protoxide of lead, till the liquid
had lost all acid reaction. By this treatment the hydrochloric
acid should be converted into the insoluble chloride of lead.
The liquid was filtered, decomposed by a current of sul-
phuretted hydrogen, boiled, and filtered a second time. It
yielded a pale-yellow fluid markedly acid, which was sub-
sequently treated with alcohol and ether by the method
already described. The liquid, after the second filtration, still
precipitated nitrate of silver, for it contained all the chloride
of sodium originally present. Although this was no real ob-
jection to the distinction of the acid from the hydrochloric, I
was anxious to satisfy myself that it could be procured quite
free from chlorine. "With this object in view, several ounces
of the liquid were boiled with a portion of carefully prepared
and crystallised sulphate of silver, till it ceased to give a pre-
cipitate with the nitrate of the same base. A current of
sulphuretted hydrogen was then passed through the liquid, to
precipitate the excess of sulphate necessarily added, after
which it was boiled and filtered. It now contained free sul-
CASE OF SARCINA VENTRICULI. 367
plmric acid, and sulphates instead of chlorides ; it was digested
on oxide of lead, until it lost all acid reaction, filtered from
the sulphate of lead and excess of oxide, and submitted again
to sulphuretted hydrogen, till a precipitate ceased to fall.
After being boiled and filtered anew, it was evaporated on
the water-bath, and digested with alcohol, which left the sul-
phates undissolved. The product of these operations, which
contained no inorganic acid, reddened litmus strongly.
" Other processes were followed which need not be detailed ;
none of them yielded an acid quite free from animal matter,
nor was it ever procured in large quantity ; but it presented
the same properties in whatever way obtained. I did not
ascertain the solubility ^of the acid in ether, till the inquiry
was nearly concluded, so that some of the experiments here-
after mentioned were made with the alcoholic solution, which
was less pure.
"The following properties were ascertained by repeated
trials to belong to this acid. It was soluble in ether, alcohol,
and water, was quite destitute of odour, and neither volatile
nor crystallisable. When the aqueous solution was digested
on phosphate of lime prepared from bones burned to white-
ness, and freed from carbonate of lime by boiling with acetic
acid, and subsequent protracted washing with water, it dissolved
a large portion of the salt ; and it acted in the same way on
the recently-precipitated phosphate. It formed a soluble salt
with oxide of silver, which strikingly distinguishes it from
hydrochloric acid. It formed soluble salts likewise with oxide
of lead, with potass, soda, ammonia, baryta, and lime ; the
last soluble also in alcohol It sustained a heat of 300 with-
out decomposition, but when the temperature was much
elevated it inflamed along with the animal matter accompany-
ing it, and suffered destruction. It was always found, however,
that the animal matter gave way before it, for after charring
had occurred to some extent, water still dissolved an acid
from the mass.
368 CASE OF SAECINA VENTRICULI.
" On comparing these properties witli the characters known
to distinguish the organic acids of animal origin, they will be
found to correspond closely with those of lactic' acid, which
accordingly I believe the acid I have been describing to be.
Hydrated lactic acid (H + C 6 H g 6 ) is stated by Berzelius *
and Liebigt to constitute a colourless syrupy liquid, inodorous,
uncrystallisable, and not volatile, but decomposed at a tem-
perature of 480. It forms soluble salts with all the metallic
oxides, and dissolves a large quantity of phosphate of lime.
There is no single decisive test of its presence, nor does it
present any other marked characteristics which could be
sought for in the acid under examination. One method there
certainly is by which the identity of this acid with the lactic
could have been ascertained an ultimate analysis namely, and
discovery of its atomic weight ; but it was impossible to put
this plan in practice. Nevertheless, I think the conclusion
will be admitted that the acid was the lactic.
" Three acids, then, were found in the liquid hydrochloric,
acetic, and lactic ; the first was present in too small quantity
to be considered a morbid product. So far as the organic
acids are concerned, it is impossible to say whether their mere
presence constitutes a morbid sign, for the statements on
record concerning the normal acids of the stomach are very
incomplete and unsatisfactory. Dr. Prout found in the
stomachs of the lower animals no acid but the hydrochloric.J
Leuretand Lassaigne found only the lactic ; Schultz only the
acetic ; || Chevreul found only the lactic in the gastric juice
of dog, and in the liquid brought up by an emetic from the
stomach of a healthy man fasting. 1[ On the other hand,
Gmelin found in the lower animals muriatic and acetic acids,
* Traite de Ckimie, tome vii. pp. 612-620.
t Turner's Chemistry, p. 996. J Phil. Trans. 1824, p. 45.
Recherches Physiologiques et Cfiimiques, p. 115.
|| Miiller's Physiology, p. 564. H Leuret et Lassaigne, op. cit. p. 117.
CASE OF SARCINA VENTRICULL 369
and in the horse butyric acid.* Dunglison, who analysed the
gastric juice from the stomach of St. Martin the Canadian,
whose case has been described by Dr. Beaumont, found
muriatic and acetic acids.t Dumas, in his Lectures on
Organic Chemistry, delivered last summer (1841), stated the
normal acids to be the muriatic and lactic.J
" To perplex the inquiry still further, Gmelin admitted no
distinction between lactic and acetic acid, or, at furthest, con-
ceived the former to be the latter modified by adhering animal
matter. Now that we know these acids to be quite distinct in
composition and properties, the observations of Gmelin, other-
wise so high an authority, lose much of their value.
" In the preceding summary of conflicting opinions it will
be observed, that whilst some chemists contend for lactic and
others for acetic acid as the normal organic acid of the gastric
juice, no one professes to have found both acids in the same
liquid, as was the case with that which I have analysed. One
of these acids, then, was abnormal, but which ? It would be
useless attempting to decide this question by an appeal to the
relative worth of the authorities quoted ; it is not improbable
that both acids are developed during healthy digestion. Lactic
acid is so abundant, free or combined, in the milk, blood, urine,
and other parts of the body, that its existence in the stomach
is almost certain. As for acetic acid, it is a much rarer con-
stituent of animal fluids, and there can be little doubt that
lactic acid has often been mistaken for it.
" In the meanwhile however, till new researches are made
on this subject, neither acid can be considered by its mere
presence as a morbid sign. I may, however, remark, that
lactic acid has already been found by Dr. Graves in the liquid
* Eecherches sur la Digestion, vol. i. pp. 166-67 ; vol. ii. p. 317.
h Miiller, op. and loc. cit.
$ Manuscript notes kindly furnished by Mr. Norton.
2B
370 CASE OF SARCINA VENTRICULI.
vomited by a sufferer from dyspepsia ;* and MM. Boutron and
E. Fremy, in a paper on the lactic fermentation, observe, ' It
is known that the liquids contained in the stomach can, in
n
certain conditions, present a strongly acid reaction. Now, the
analyses made on this subject demonstrate, in these liquids,
the presence of lactic acid/t
" One thing, however, is certain, and it is the main truth
elicited by the analysis viz. that the quantity of acetic acid
found in this case was enormous. Although we have no
account of the proportion discovered in the gastric juice or
chyme, by those who maintain its presence there, it is certain
that the quantity must be very small. Prout overlooked the
presence of an organic acid altogether, and Gmelin, the great
advocate of its existence, found only traces of it. But the
quantity of liquid ejected at once by the patient often
amounted to more than two quarts, which would contain
eighteen grains of acetic acid ; and the amount is rather
understated, for some portions of the liquid were necessarily
lost in the distillations, which, moreover, were never pushed
to dryness.
" I am not aware of any case on record corresponding to
this ; but I forbear at present forming any opinion as to
whether this remarkable development of acetic acid, and the
occurrence of the curious organisms described by Mr. Goodsir,
were mutually dependent or merely coincident.
" The liquid otherwise was not particularly examined as to
its salts or animal matter."
Those who know the doubt which at present exists as to
the acids which are found in the stomach in health and
* Transactions of the Association of Fellows and Licentiates of the College
of Physicians in Ireland, 1804, vol. iv. Quoted in Tiedemann and Gmelin,
vol. i. p. 167.
t Annales de CJiimie et de Physique, 3me serie, torn. xh. 1841.
CASE OF SARCINA VENTRICULI. 3*71
disease, will perceive the value of the foregoing analysis.
Other questions arising out of the consideration of the case,
as well as its future progress, will be taken up and recorded
in future communications on healthy and morbid digestion
subjects with which Dr. Wilson and I are at present
engaged.
3*72 ULCERATION OF PEYER'S PATCHES
XIX. ON A DISEASED CONDITION OF THE
INTESTINAL GLANDS *
WITHOUT entering upon the question, as to whether the
subject of the present paper constitutes a distinct species of
disease, or be merely a form of the ordinary continued fever
a question which I am quite satisfied will never be answered
so long as each pathologist confines the inquiry to the fever
of his own district, without connecting with it the consider-
ation of those forms of fever which occur in every separate
district of a country or continent I shall proceed at once to
describe a lesion which I observed some time ago in a disease
which I was led to consider as typhus or continued fever.
On opening the abdomen of individuals who had died of
this fever, we could always recognise the diseased condition
of the internal surface of the gut by the elongated bluish
purple spots on its peritoneal surface, corresponding to the
glands of Peyer on the internal surface ; and this we could
do, even in those cases in which, from other circumstances,
the vascularity of the parts had disappeared after death.
On laying the gut open, the patches of Peyer's glands ex-
hibited, according to the standing of the case, the various
appearances which I shall now describe.
But before proceeding to detail the phases through which
the patches pass, from the first appearance of the disease till
the establishment of the typhous ulcer, or of perforation, I
* Read before the Med.-Chir. Soc., February 1842, and printed in the
London and Edinburgh Monthly Journal of Medical Science, April 1842.
IN CONTINUED FEVEK. 373
may remark, in regard to the condition of the mucous mem-
brane in the neighbourhood of the patches, that it did not in
every case exhibit unequivocal traces of inflammatory action.
It might be highly congested, or it might be perfectly blood-
less in cases of well-developed disease of these patches. I
cannot say that I have often observed the mucous membrane
pulpy or softened. The villi and follicles of Lieberkuhn have
always appeared to me to be healthy. The vascularity, when
it did occur, was met with principally in the neighbourhood
of the glandular patches, and resembled in all respects that
described and figured by Dr. Bright in his report on the form
of fever lesion now before us.
The commencement of the disease is first announced by
the smaller patches becoming slightly elevated, so as to be
hemispherical or conical, and by the more extended groups
assuming a table-like appearance, with perpendicular edges,
as if a flat plate had been placed on the mucous surface. The
colour varies, according to the case, from bright carmine red
to dark purple or black, continuous or in patches. In the
more vascular specimens, the colour is a yellowish grey, con-
trasting with the dead white or greyish- white of the intestinal
surface. More closely examined the surfaces of the patches
exhibit, as usual, the follicles of Lieberkuhn and villi, differing
in no respect from those on a healthy surface, and arranged
around the vesicles of the patch in the usual manner. An
examination of this kind must be made under water, and
when conducted in this manner the vesicles of the patch may
be seen by floating aside the membranous border and circle of
villi which surround each of them. The vesicles themselves
may thus be seen to be much distended with a yellowish
matter a distension which is now perceived to be the imme-
diate cause of the elevation of the patch.
In the second stage of the disease, the patches still con-
tinue to rise above the surrounding surface, and to exhibit the
374 ULCERATION OF PEYER'S PATCHES
changes formerly described, in a more characteristic manner.
As the elevation increases, a change begins to take place on
the elevated surface. This change may be partial that is to
say, it may take place sooner on some parts of the patch than
on others ; but generally it extends over the whole surface, and
is bounded by a line situated from a 10th to a 16th of an
inch from the edge of the patch. The change itself consists
in the surface beginning to alter in colour, becoming dirty-
yellow or grey, and assuming a peculiar undulating or con-
torted surface, like a bit of leather seared with a hot iron.
The villi have now in a great measure disappeared, but the
orifices, or rather the circular folds or pits, in which are
situated the vesicles, are still visible. At last the confines of
the changed portion of the patch are rendered evident by a
groove apparently produced by ulceration, which, appearing
here and there on these confines, at last extends all round,
and indicates some change about to take place in the whole
arrangement of the parts.
In the third stage, the groove just described makes its way
into the tissues ; and as it does so, the healthy but elevated
mucous membrane on its external edge gradually everts
itself, as if by the upward pressure of the matter beneath it.
While this is going on, the edges and surface of the altered
portion become more rugged, and their former character
somewhat obscured. The altered portion, which now assumes
very much the appearance of a slough tinged with intestinal
matters, becomes more and more detached from the surface
to which it adheres. When the mass is gently raised under
water, it may be observed that its attached surface sends
processes down into the cellular membrane beneath ; and if
these processes be carefully drawn out, they will be found to
correspond each with one of the original vesicles of the patch.
When detached in this manner, they leave on the surface to
which they adhered, dimples, or rather pits, which may be
IN CONTINUED FEVER. 375
recognised as being the cellulo-vascular sheaths of the patch-
vesicles.
Occasionally the free surface of the altered portion comes
away first, in the form of flocculent laminae, and the deep pro-
cesses continue to be attached for some time in the cellulo-
vascular capsules, like little nodules or pellets of a rounded
or pyriform shape.
The altered portion, even immediately before detachment,
may still present on its surface traces of its original structure.
The orifices of the follicles in which the vesicles are situated
are visible here and there on the surface, and the membrane
retains sufficient consistence to bind the mass together.
Fourth stage. When the sloughy mass has separated, the
surface of what may now be called an ulcer appears flocculent ;
but, when examined under water with a couple of needles, a
number of foveae, the remains of the cellulo-vascular capsules,
may be observed on it. In some of these, the little pellets
of deposit may still remain attached, appearing like mustard-
seeds scattered over the surface. The edges of these ulcers
are thick and everted, and exhibit the natural structure of
the mucous membrane. In some ulcers the eversion of the
edges proceeds so far as to throw the mucous surface of the
edge completely over, so as to apply it to the surrounding-
mucous membrane.
Fifth stage. The ulcer may now heal, or proceed to per-
foration of the gut. In the former case, granulations, I pre-
sume, appear, and the reaction of these cellular elements
carries on the contraction and cicatrisation so well displayed
in some of the preparations on the table. In the present
form of ulcer, as in others affecting the mucous coat of the
bowels, it is some time before villi again make their appear-
ance on the cicatrised surface ; but these changes I have not
watched or observed. When the ulceration proceeds towards
perforation, it is generally one spot of the. patch which is
376 ULCERAT10N OF PEYER'S PATCHES
more particularly affected, the rest of the ulcer retaining its
former granulating or flocculent appearance. At this stage
of the process lymph begins to be deposited on the external
surface of the gut ; and if the patient survives the perfora-
tion eight or ten hours, the lymph rounds off the edges of the
hole, and gives it that punched-out appearance so frequently
observed. The omentum may adhere opposite the incipient
perforation, and after contraction has concluded, it appears
as if it had been forced from without into the hole, an
appearance resulting from the contracting agency of the
granulations.
Having now described the changes which the patches
undergo in this form of disease, I have to point out the
peculiar matter upon the presence of which these changes
appear to depend. The grey matter which fills the vesicles
or the spaces which they occupy, I find to consist of that
universal element of every primitive tissue, healthy or
diseased nucleated cells. These cells are from 2000 to 4000
of an inch in diameter. They do not in general exhibit a
nucleus in the sense in which that term is generally applied ;
that is, the individual cells do not present in their interior
smaller cells holding certain relations to them. These cavities
appear to contain a number of granules, four, five, or six, as
far as could be reckoned. Whether these in the aggregate
are to be considered as a nucleus proceeding towards the
formation of a number of young cells, or whether the appear-
ance is to be considered as analogous to that irregular form
of nucleus and cell-contents characteristic of certain forms of
tubercle, I do not know. This matter, of whatever nature it
may be, appears first in the vesicles of the patches, and then
spreads out on all sides, after the manner of other purely
cellular structures, till the whole patch, before it is thrown
off, appears to be principally formed of it ; the surface of the
mass, however, as has been stated, and certain parts of its
IN CONTINUED FEVER. 37*7
interior, consisting of the somewhat altered mucous and sub-
mucous tissue.
The morbid changes which the glandulse aggregates of the
ileum undergo during continued fever, appear, from the
observations I have just detailed, to be of the following
nature viz. the development of cells within the constituent
vesicles of the patches to such an extent as at last to burst
them, or cause their solution; the continued increase in the
number of the cells, proceeding from as many centres as there
are vesicles in the patch ; the conglomeration of the whole
into one mass above the submucous and under the mucous
membrane ; the distension of the latter, and the necessary
ulceration and sloughing of the mass arising from this circum-
stance.
The whole mass'; as detached from the gut, is not there-
fore to be considered as a slough ; that portion only which
consists of the upper halves of the vesicles and of the mucous
membrane being dead ; the greater part, consisting of the
cellular mass, being merely detached from the submucous
tissue, consists of those nucleated cells, which, at first con-
fined within their generative vesicles, had at last vegetated
so much as to break their natural bounds, and become one
mass of cells, constantly increasing in numbers, except below,
where the separate centres from which they originally pro-
ceeded are indicated by the processes and little pellets which
are situated in the remains of the vesicle-capsules.
It will have been observed that I have not employed the
term " inflammation " in the course of the description I have
just given. Whether the changes I have described originate
in inflammatory action or not, of this I am certain, that the
ulceration and pseudo-sloughing is an immediate effect of the
distension from the submucous vegetating mass, and would
occur whether the latter were produced by inflammation or
not.
378 ULCERATION OF PEYER'S PATCHES IN CONTINUED FEVER.
In regard to the history of this department of the morbid
anatomy of fever, I may state that Dr. Bright has given very
beautiful representations of the sloughs and ulcers in his
Reports of Medical Cases. Louis and Chomel have referred
to the appearance of the matter which distends the glands,
and compared the process to the tuberculous. Schonlein, in
his General P.athology, has made a general allusion to the de-
posit, and to the changes which occur in the patches.* Gruby,
in a work on the Microscopic Character of Morbid Products,"^
was the first, as far as I can learn, who figured and described
the cells of which the deposit consists. Finally, KokitanskyJ
has generalised the subject, and considered the matter de-
posited as peculiar to typhus fever, and referable to the same
category as cancer, tubercle, etc.
My own observations have been made without reference
to any hypothesis as to the pathology of fever.
* Schonlein, Allgemeine und specielle Pathologic und Therapie, Zweiten
Thiele, 1839, p. 23.
t Obs&rvationes Microscopicce auctore Dav. Gruby, 1840, p. 44.
J Rokitansky, Handbuch der Patlwlogischen Anatomic, band iii. p. 265.
PATHOLOGY OF KIDNEY AND LIVER. 3*79.
XX. OBSEEVATIONS ON THE STEUCTUEE AND
SOME OF THE PATHOLOGICAL CHANGES
OF THE KIDNEY AND LIVER*
EESEARCHES into the structure of the healthy human kidney,
and into the changes which it undergoes in the granular
degeneration described by Dr. Bright, have led me to the
following conclusions :
Without denying the existence of occasional blind extremi-
ties of the tubuli uriniferi, the result probably of arrested
development, I may state that I have never seen the ducts
terminating in this way. I have observed a structure which
appears hitherto to have been overlooked by anatomists
namely, a fibro-cellular framework, which, pervading every
part of the gland, and particularly its cortical portion, per-
forms the same important part in the kidney which the cap-
sule of Glisson does in the liver forming a basis of support
to the delicate structure of the gland, conducting the blood-
vessels through the organ, and forming small chambers in the
cortical portion, in each of which a single ultimate coil or
loop of the uriniferous ducts is lodged. I believe that the
urine is formed at first within the so-called epithelium-cells
of the ducts ; and that these burst, dissolve, and throw out
their contents, and are succeeded by others which perform
the same functions. The urine of man has not been detected
by me within the cells which line the ducts, but I have sub-
mitted to the Eoyal Society of Edinburgh, within the last few
x * Read before Medico-Chirurgical Society, Edinburgh, May 1842.
380 STRUCTURE AND PATHOLOGY
weeks, a Memoir,* in which it is proved that the urine, bile,
milk, as well as the other more important secretions in the
lower animals, are formed within the nucleated cells of the
gland-ducts. I believe, therefore, that the urine of man is
poured at first into the cavities of the nucleated cells of the
human kidney. I do not pretend to decide whether the
morbid changes in the kidneys, in the various stages of the
granular disease of Bright, originate in inflammation or simply
in congestion of the gland, but may remind the Society of
those changes which, at a former meeting,! I announced as
occurring in the vesicular glands of the intestine during
fever namely, the formation and progressive increase of
nucleated cells (probably aberrant forms of the epithelium
which lines the vesicles) within the vesicles of the patches,
and may now state that granular degeneration of the kidney
has a similar increase ; that it consists essentially of the
formation of nucleated cells within the uriniferous ducts ;
that these new cells were principally confined to the ultimate
loops of the ducts, but that, in advanced stages of the disease,
they may be formed even in the tubes of the pyramids of
Ferrein ; that when a single ultimate loop of the uriniferous
ducts was gorged, or distended with the increasing mass of
germinating cells, or when two or more neighbouring loops
were in this condition, the little mass constituted one of the
granulations characteristic of the milder forms of the disease ;
that when throughout the gland, or in certain portions of it,
the germinating masses had so far distended the ducts and
loops as to cause their disappearance, and to induce absorp-
tion of the walls of the little chambers of the fibro-cellular
capsule, and consequently of the uriniferous ducts, the whole
of the cortical portion of the gland, or that part of it more
particularly affected, assumed the appearance presented in
* See the Memoir " On Secreting Structures," No. XXV. of this volume,
t See No. XIX. of this volume.
OF KIDNEY AND LIVER. 381
the more advanced stages of the disease. If the patient sur-
vive the stage last described, the kidney becomes partially or
wholly atrophied a change due to the contraction of fibrous
tissue, produced either from the cells which constitute the
disease or from cells resulting from effused fibrin. With the
exception of the primary engorgement of the capillary system,
and of the Malpighian corpuscles, and their subsequent dimi-
nution, I have not observed any very marked change in the
vascular system of the kidney during granular degeneration
of the organ.
In proceeding to describe certain parts of the healthy and
morbid structure of the human liver, I may observe that very
little remains to be done in reference to this gland, since the
very admirable researches of Mr. Kiernan. In regard to two
parts of the structure, however, we are yet quite in the dark
namely, the mode of termination of the hepatic ducts and the
connection between them and the nucleated cells of this
organ ; but have been able, after considerable difficulty, to
verify Mr. Kiernan's supposition that the hepatic ducts
terminate by a network within the lobules of the liver,
around the intra-lobular veins. But the most important
feature in my observations is the detection of the real con-
nection between these ultimate ducts and the nucleated cells,
which are grouped in the form of acini on the sides of the
duct. Each acinus may consist, first, of a single cell, the
primary or germinal cell of the future acinus ; or, secondly,
of two or more cells enclosed in the primary cell, and pro-
duced from its nucleus. The enclosed cells may be named
the secondary cells of the acinus ; and in the cavities of these,
between their nuclei and cell-walls, the bile and a few oil-
like globules are contained, as has been already stated, in the
memoir above alluded to. The primary cell, with its included
group of cells, each full of bile, is appended to the side of the
remote ducts, and consequently does not communicate with
382 STRUCTURE AND PATHOLOGY
that duct a diaphragm formed by a portion of the primary
cell-wall stretching across the pedicle. When the bile in the
group of included cells is fully elaborated, the diaphragm
dissolves or gives way, the cells burst, and the bile flows along
the ducts ; the acinus disappearing, and making room for a
neighbouring acinus, which has in the meantime been advanc-
ing in a similar manner. The whole parenchyma of the liver,
then, is in a constant state of change of development,
maturity, and atrophy this series of changes being directly
proportioned to the profuseness of the secretion of bile. I find
myself anticipated by Mr. Bowman in regard to one of the
morbid conditions of the human liver namely, the fatty liver ;
and have much pleasure in confirming that gentleman's obser-
vations (Lancet, Jan. 1842), as to the fat being deposited
within the nucleated cells of the organ, and to be considered,
in fact, as a redundancy of the oil-globules naturally existing
in these cells. As in the kidney, so in the liver, contractile
fibrous tissue may be developed, and produce partial or com-
plete atrophy. Dr. Carswell had already indicated this as
existing in cirrhosis. The matter, of which the rounded
masses in cirrhosis consists, is not a new deposit, but merely
the natural tissue of the liver, altered by the pressure exerted
by their fibrous envelopes. These alterations consist in con-
striction, more or less powerful, of the vessels and ducts
which pass out and in to the rounded mass, the necessary
difficulty with which the circulation is carried on, and the
bile advanced along the ducts ; and, latterly, in a change in
the constitution of the nucleated cells themselves, which,
instead of being distended with bile containing oil-like
globules, contain matter of a darker colour, and less oil.
The cells may at last contain matter perfectly black, and then
the rounded mass assumes the appearance of a melanotic
tubercle, the black cells in some instances becoming pyriform
and caudate. I am inclined to believe that the forms of
OF KIDNEY AND LIVEK. 383
cirrhosis and melanosis are due to the contractile tissue, as a
product of inflammatory action more or less acute. The
action of remedies, particularly of mercury, would appear to
corroborate this opinion. From the observations made on the
morbid anatomy of the human liver and kidney, I conclude
that certain of the diseases of those organs are due to the
development of new cells and new matter within the ducts
and nucleated cells of the organs, in accordance with the
normal laws of cellular development this cellular vegetation
at last destroying, more or less completely, the natural tissue
of the organ.
APPENDIX TO PEECEDING PAPEE.
[The following more detailed observations on the relation
of the secreting cells to the bile-ducts, and of the distribution
of the connective tissue in the liver, occur in a manuscript
essay, we believe unpublished, entitled " A General View of
the Healthy and Morbid Anatomy of the Liver." The obser-
vations on the relations of the cells and ducts are especially
interesting in connection with the recent descriptions of
Hering (Schultze's Archiv, 1867) and others on this subject,
whilst the careful description of the distribution of the areolar
texture, shows how thoroughly Professor Goodsir recognised
the importance of this tissue in its relations to the pathology
of the organ. There is no date attached to the essay, but from
the appearance of the paper and ink it had evidently been
written many years ago. EDS.]
In the liver, as in every other gland, secretion is performed,
not by the vessels, but by the particles which form its paren-
chyma. In glands generally these particles are packed in the
form of a layer on the internal surface of the fine membrane
(germinal or primary membrane) of the ducts, from their open
384 STKUCTUKE AND PATHOLOGY
mouths to their blind or anastomosing extremities. In the
liver the arrangement is different, although in principle the
same. Tracing the structure of the ducts from the transverse
fissure up along the portal passages, where they accompany
the vena portse and hepatic artery on to the compressed spaces
between the lobules, and where they form a network, they
consist of a fine membrane, having vessels on its external,
compressed particles (epithelia) on its internal surface. At
the outer surface of the lobules, the fine membrane of these
ducts does not seem to enter the lobules ; only the portal
vessels, and the secreting particles, the latter being grouped
around the former, so as to leave passages continuous with
the plexus of ducts on the external surface of the lobule, con-
verging, and at the same time communicating, with one
another from that surface to the centre of the lobule. If, then,
we suppose the portal vessels, which pass in at the outer part
of the lobule, the hepatic vein, which passes out at the base,
and the intermediate capillary plexus to be removed, we shall
have remaining in a lobule only a mass of flattened particles
so arranged as to exhibit two sets of passages one occupied
by the vessels of the lobule, and communicating on the one
hand with the portal, and on the other with the hepatic vessels.
The other set of passages within the lobules are continuous
with the hepatic ducts, and are the ducts of the lobule itself.
The difference, then, between an extra and an intra-lobular duct
is that the former possesses a fine membrane between its
vessels and secreting particles ; the latter presents no such
membrane, the particles being so arranged as to be in the
immediate neighbourhood of bloodvessels, and to leave free
intercellular passages outwards for their secretion.
The lymphatics of the liver I am inclined to believe, for
reasons which I cannot enter upon at present, to take their
origin in the intercellular spaces of the lobule, to acquire
distinct walls in the compressed portal spaces between the
OF KIDNEY AND LIVER. 385
lobules. They then pass, some along the portal passages to
the transverse fissure, others up between the lobules to the
sub-peritoneal areolar texture of the diaphragmatic surface of
the gland. The ducts of the liver may therefore be considered
as communicating directly with the lymphatic system.
The areolar texture of the liver is of great pathological
importance. There are two situations in which it can exist
in this organ the portal passages and those for the hepatic
veins. In the latter situation it is extremely limited in
amount and very dense, connecting firmly the bases of all the
lobules to the sub-lobular veins, continuous, on the one hand,
around the trunk of the hepatic vein with the areolar texture
of the posterior region of the cavity of the abdomen ; on the
other, around the bases of the lobules with the areolar texture
of the portal canals. Lymph and pus do not appear to be de-
posited in the areolar texture of the hepatic passages, for so
firmly are .the lobules attached to the veins, that when the tex-
ture of the organ is broken up by an abscess, the lobules
adhere, in the form of masses of parenchyma, to the branches
of the hepatic vein, the pus breaking up the texture in the
direction of the portal passages and interlobular spaces.
The second and more important division of the areolar
texture occupies the interlobular spaces, is continuous along
these with the subserous areolar texture, and, passing along
the portal passages, is continuous with the areolar texture of
the gastro-hepatic omentum at the transverse fissure. In the
interlobular portion of this division of the areolar texture the
interlobular plexus of the portal veins and the hepatic ducts
are situated. In its continuation under the peritoneum the
branches of the hepatic artery for the serous membrane, as well
as the superior lymphatics of the liver, lie. In the portal pas-
sages the areolar texture, or capsule of Glisson, contains the
trunks and branches of the vena portae, the hepatic artery, ducts,
nerves, and inferior lymphatics, also the vaginal branches of the
2c
386 STRUCTURE AND PATHOLOGY OF KIDNEY AND LIVER.
vein, artery, and duct. This division of the areolar texture is
in certain respects the most important pathological element
of the organ. It is the seat of the more important inflamma-
tions, of the effusions of pus and lymph, of chronic inflamma-
tion, and of the fibrous lymph, producing cirrhosis and atrophy,
and probably of the heterologous formations, or cancers, which
attack the organ.
ANATOMICAL AND PATHOLOGICAL
OBSERVATIONS.*
"Although it shew not the agent, yet it sheweth a rule and analogy in
nature, to say that the solid parts of animals are endued with attractive powers,
whereby, from contiguous fluids, they draw like to like ; and that glands have
peculiar powers attractive of peculiar juices." BERKELEY.
"Even herein consists the essential difference, the contradistinction, of an
organ from a machine ; that not only the characteristic shape is evolved from
the invisible central power, but the material mass itself is acquired by assimi-
lation. The germinal power of the plant transmutes the fixed air and the ele-
mentary base of water into grass or leaves ; and on these the organiflc principle
in the ox or the elephant exercises an alchemy still more stupendous. As the
unseen agency weaves its magic eddies, the foliage becomes indifferently the bone
and- its marrow, the pulpy brain or the solid ivory. " COLERIDGE.
" The greater part of my share of these Anatomical and
Pathological Observations will be already, to a certain extent,
familiar to those who attended my lectures, in the theatre of
the Eoyal College of Surgeons, in summer 1842, and winter
1842-3.
" The Memoir on the Secreting Structures is reprinted in
a modified form from the Transactions of the Royal Society
of Edinburgh for 1842, and that on the Intestinal Villi from
the Edinburgh Philosophical Journal of the same year.
Those on the Placenta and Lymphatic Glands were read in
the Eoyal Society of Edinburgh in 1843, but were not sub-
* The thirteen succeeding Memoirs were published by Macphail, Edinburgh,
1845, in an octavo volume, entitled Anatomical and Pathological Observations,
and were preceded by the accompanying preface. (Eos.)
388 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
mitted for publication. Abstracts of some of the others have
also appeared, from time to time, in the reports of various
Societies.
" The observations on the healthy Structure and Economy
of Bone are, with the exception of those on the contents of
the corpuscles, an abstract of my lectures on this subject in
the College of Surgeons in winter 1842-3. I have considered
this explanation necessary, in consequence of the resemblance
between certain parts of my description and those in the
admirable chapter on the same subject in Todd and Bowman's
Physiological Anatomy, drawn up from the observations of
Mr. Tomes.
" My brother, Harry D. S. Goodsir, has added some of his
own zoological, anatomical, and pathological observations, as
confirmatory of the doctrines of Centres of Nutrition and of
Secretion. (Nos. XXVI. XXXII. XXXIII.)
" To such as may be inclined to object to the theoretical
views which run through and connect these anatomical details,
I would only say, that we shall be quite satisfied, if, on find-
ing the latter correct, they will allow us to retain the former
for future use ; feeling assured, that * there is a certain analogy,
constancy, and uniformity, in the phenomena or appearances
of nature, which are a foundation for general rules ;' and that
' these are a grammar for the understanding of nature, or that
series of effects in thevisible world, whereby we are enabled
to foresee what will come to pass in the natural course of
things.' "
VolJL
Plate, JV
14
IS
16
17
CENTKES OF NUTRITION. 389
XXI. CENTEES OF NUTEITIOK (PLATE IV.)
BY centres of nutrition I understand certain minute cellular
parts existing in the textures and organs. With many of these
centres anatomists have been for some time familiar,* but with
a few exceptions have looked upon them as embryonic struc-
tures.! I am inclined to believe in the general existence of
such centres, for a certain period at least, in all textures and
organs, and to this I wish to direct attention at present.
The phenomena presented by these centres incline me to
regard them as destined to draw from the capillary vessels, or
from other sources, the materials of nutrition, and to distri-
bute them by development to each organ or "texture after its
kind. In this way they are to be considered centres of
germination ; and I have elsewhere named them germinal
spots adopting the latter term from the Embryologists. j"
The centre of nutrition with which we are most familiar,
is that from which the whole organism derives its origin
the germinal spot of the ovum. From this all the other
centres are derived, either mediately or immediately ; and in
directions, numbers, and arrangements, which induce the con-
figuration and structure of the being. As the entire organism
* The nuclei of the textures.
f Mr. Bowman, in his Paper on Muscle, Philosophical Transactions, 1840,
Part I. page 485.^ Cyclopaedia of Anatomy and Physiology, art. "Muscle."
Dr. Martin Barry, in the Philosophical Transactions, and most explicitly in his
Paper " On the Corpuscles of the Blood," 1841, Part I. page 269, paragraph 83.
Trans. Roy. Soc. Ed. 1842. "On the Secreting Structure, and the Laws
of its Functions."
390 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
is formed at first, not by simultaneous formation of its parts,
but by the successive development of these from one centre,
so the various parts arise each from its own centre, this being
the original source of all the centres with which the part is
ultimately supplied.
From this it follows, not only that the entire organism, as
has been stated by the authors of the cellular theory, consists
of simple or developed cells, each having a peculiar inde-
pendent vitality, but that there is, in addition, a division of
the whole into departments, each containing a certain number
of simple or developed cells, all of which hold certain rela-
tions to one central or capital cell, around which they are
grouped. It would appear that from this central cell all the
other cells of its department derive their origin. It is the
mother of all those within its own territory. It has absorbed
materials of nourishment for them while in a state of develop-
ment, and has either passed them off after they have been
fully formed, or have arrived at a stage of growth when they
can be developed by their own powers.
Centres of nutrition are of two kinds those which are
peculiar to the textures, and those which belong to the
organs. The nutritive centres of the textures are in general
permanent. Those of the organs are in most instances pecu-
liar to their embryonic stage, and either disappear ultimately
or break up into the various centres of the textures of which
the organs are composed.
A nutritive centre, anatomically considered, is merely a
cell, the nucleus of which is the permanent source of succes-
sive broods of young cells, which from time to time fill the
cavity of their parent, and carrying with them the cell-wall
of the parent, pass off in certain directions, and under various
forms, according to the texture or organ of which their parent
forms a part.*
* For the first consistent account of the development of cells from a parent
CENTRES OF NUTRITION. 391
There is one form in which nutritive centres are arranged,
both in healthy and morbid parts, which is frequently alluded
to in the following chapters, and which may be named a
germinal membrane.* In a germinal membrane, the nutritive
or germinal centres are arranged at equal or variable distances,
and in certain directions, in the substance of a fine trans-
parent membrane. A germinal membrane is occasionally
found to break up into portions of equal size, each of which
contains one of the germinal centres. From this it is per-
ceived that a germinal membrane consists of cells, with their
cavities flattened, so that their walls form the membrane by
cohering at their edges, and their nuclei remain in its sub-
stance as the germinal centres.
Germinal membranes are only met with on the free
centre, and more especially of the appearance of new centres within the ori-
ginal sphere, we are indebted to the researches of Dr. Martin Barry. "What-
ever may be said in opposition to Dr. Barry's views regarding the functions of
the blood-globules, and the structure of muscular fibre, he is yet entitled,
above all physiologists of the present day, to the merit of having kept steadily
before him in his researches the principle of the central origin of all organic
form.
* The membranous tubes of glands on which the epithelium is situated
were described by Henle, Miiller's Archiv, 1839. Mr. Bowman (Phil. Trans.
1842) " On the Structure and Use of the Malpighian Bodies of the Kidney," etc.,
has applied to the membrane of these tubes the very appropriate name of
Basement Membrane. This membrane I consider to be a primary or germinal
membrane. The term, basement membrane, is good as involving no
hypothesis ; it is therefore a most appropriate descriptive term. I have always
considered the basement membrane, or elementary membrane of glands, as a
form of the primary cells of glands, and the source of the secondary or
secreting cells, and have therefore been in the habit of naming it primary, or
germinal membrane. Mr. Bowman considers it to be simple, or homogeneous.
This is true as far as it contains no bloodvessels, and as regards its external
or attached layer ; but as in its original condition it consists of cells, and when
perfect contains nuclei at equal or variable distances, I do not consider it as
simply molecular. These nuclei, or germinal spots, may be certain of the
epithelial cells, which become mother-cells, between the two layers of the
membrane ; or cells belonging to the order of the nuclear fibres of Valentin
and Henle.
392 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
surfaces of parts or organs. One surface of the membrane
is therefore attached, and is applied upon a layer of areolar
texture, intermixed with a more or less rich network of
capillary vessels. The other surface is free, and it is on it
only that the developed or secondary cells of its germinal
spots are attached. These secondary cells are at first con-
tained between the two layers of the membrane, these layers
being the opposite walls of each of its component cells.
When fully developed, the secondary cells carry forward the
anterior layer, which is always the thinnest, leaving the
nuclei or germinal centres in the substance of the posterior
layer in close contact with the bloodvessels.
Of the forces which exist in connection with centres of
nutrition, nothing very definite can yet be stated. When this
branch of inquiry shall have been opened up, we shall expect
to have a science of organic forces, bearing direct relations to
anatomy, the science of organic forms.
ON THE INTESTINAL VILL1. 393
XXII. THE STEUCTUEE AND FUNCTIONS OF
THE INTESTINAL VILLL (PLATE IV.)
MR. CRUIKSHANK, in treating of the orifices of the Lacteals
and Lymphatics,* states that he and Dr. William Hunter
observed the openings by which the lacteals communicated
with the cavity of the gut in portions of the intestine of a
woman who died after eating a hearty supper. The two
preparations of the intestine on which these anatomists made
their observations, came into the possession of the College of
Surgeons in Edinburgh, as part of the collection of the late
Sir Charles Bell.
I removed one of the villi from Mr. Cruikshank's prepara-
tion, and had no difficulty in recognising what had been
described and figured by the original owner of the preparation.
With a low power the extremity of the villus appeared
bulbous and opaque. With a higher power I observed that
this opacity was due to the existence, at the extremity of the
villus, of a number of vesicles of different sizes. The larger
vesicles were pretty uniform in size, and about twenty in
number. The smaller were of different sizes, and more
numerous, and appeared gradually to pass into the granular
texture of the attached extremity of the villus. No blood-
vessels could be detected, but along the neck of the villus
distinct traces of two or more opaque lacteals were visible.
The vesicles and the lacteals, when viewed by transmitted
light, were of a light brown colour ; but when examined as
opaque objects, they stood out of a dead white appearance,
* William Cruikshank, The Anatomy of the Absorbing Vessels of the Human
Body, 2d ed. 1790, page 56.
394 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
contrasting strongly with the semi-transparency of the
surrounding texture. Eepeated examinations of these pre-
parations satisfied me that Dr. William Hunter and Mr.
Cruikshank were quite correct in describing and figuring
radiating lacteals within the villi, but that they were led into
error in describing those vessels as opening on the free surface
of the gut, partly by imperfect instruments and methods of
observation, partly by the general prejudice of the period in
favour of absorbent orifices. I also satisfied myself of what
appeared highly probable from the commencement of the
observations, that the villi, when turgid with chyle, were
destitute of their ordinary epithelial covering.* This circum-
stance I could not avoid connecting with the fact of the
stomach throwing off its epithelia during the process of
digestion. I determined, therefore, to investigate the process
of absorption of chyle in fresh subjects, as the facts exhibited
in Mr. Cruikshank's preparations indicated the probable
existence of complicated processes going on in villi during
digestion. The analogy of the vesicular bulbous extremity of
the villus, to the spongiole of the vegetable, forced itself upon
me, and the existence of milky chyle, within closed cells, led
me to anticipate an explanation of some of the phenomena
of digestion.
A dog was fed. Three hours afterwards he was killed.
The lacteals were turgid, and the gut was found to be full of
milky chyme, with an admixture of thin brownish fluid of a
bilious appearance. The milky matter was situated princi-
pally towards the mucous membrane ; the brown fluid
occupied the cavity of the gut.
The white matter consisted of a transparent fluid, with a
few oil-globules and numerous epithelia.
Some of the epithelia I recognised as those which cover
the villi. They were pointed at their attached extremities,
* This opinion was subsequently abandoned by the author. (Eos.)
ON THE INTESTINAL VILLI. 395
flat at the other. Many of them were single, others were
united in bundles, adhering principally by their flat or free
extremities, as if a fine membrane passed over and connected
the edges of their extreme surfaces. Occasionally these
epithelia presented a distinct nucleus ; but generally, and
whether single or in bundles, they exhibited in their interior
a group or mass of oil-like globules, which, when viewed as
opaque objects, had a peculiar semi-opaque or opalescent
appearance.* Others of the epithelia, contained in the chyme,
were prismatic, single, or in columns. They were the lining
epithelia of the follicles of Lieberkuhn, and presented the
usual nuclei.
The mucous membrane displayed the villi turgid, as if in
a state of erection, and as I had anticipated, naked or destitute
of epithelia, except at their bases, where a few still adhered.
Each villus was covered by a very fine smooth membrane,
which, from its free bulbous extremity, passed on to its sides,
and became continuous with the germinal membrane of the
follicles of Lieberkuhn. These villi, when removed from the
mucous membrane, and examined with a low power, were
semi-transparent, except at their free or bulbous extremities,
which appeared both by direct or transmitted light white and
opaque. Under higher powers the summit of the villus,
somewhat flattened, was observed to be crowded, immediately
under the membrane before mentioned, with a number of per-
fectly spherical vesicles. These vesicles varied in size from
1000 to less than 2000 of an inch. The matter in their
interior had an opalescent milky appearance. Towards the
body of the villus, on the edges of the vesicular mass, minute
granular or oily particles were situated in great numbers, and
gradually passed into the granular texture of the substance of
the villus.
Is this appearance due to a partial absorption of chyle by these protec-
tive epithelia ?
396 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
The trunks of two lacteals could be easily traced up the
centre of the villus, and as they approached the vesicular mass
they subdivided and looped. In no instance could one of
these lacteals be traced to any of the spherical vesicles, nor
could any direct communication between the structures be
detected.* The bloodvessels and capillaries, with their
columns of tawny blood disks, could be seen passing in
radiating lines and in loops across the villus, immediately
under the fine membrane already mentioned. This membrane,
perceptible on the body and neck of the villus only by the
smooth surface it presented, was most distinctly traced at the
free extremity of the villus, as it passed from the surface
of one vesicle on to that of another.t The vesicles, pushing
the membrane forward, and grouped together in masses on its
attached surface, gave the extremity of the villus the appear-
ance of a mulberry. When viewed on a dark ground as an
opaque object, the point directed to the light, a villus in
this condition is remarkably beautiful, the play of the light
on the surface of the highly-refractive semi-opaque and
opalescent vesicles giving them the appearance of a group of
pearls.
In villi turgid with chyle, which have been kept for some
time in spirits, the contents of the vesicles are opaque, the
albumen having become coagulated.
To understand the part which the vesicles of the villus
play in digestion, it is necessary to be aware of certain of the
functions of the cell, with which physiologists are yet un-
acquainted. Not only are these bodies the germs of all the
tissues, as determined by the labours of Schleiden and
Schwann, but are also the immediate agents of secretion. A
* See Gulliver's translation of Gerber's General Anatomy, pp. 272 and 273.
+ Mr. Bowman, in the article "Mucous Membrane," Cyclopaedia of Ana-
tomy, does not admit this portion of the membrane. It certainly cannot be
detached as a separate membrane.
ON THE INTESTINAL VILLI. 397
primitive cell absorbs from the blood in the capillaries the
matters necessary to enable it to form, in one set of instances,
nerve, muscle, bone, if nutrition be its function ; milk, bile,
urine, in another set of instances, if secretion be the duty
assigned to it. The only difference between the two functions
being, that in the first, the cell dissolves and disappears
among the textures, after having performed its part ; in the
other, it dissolves, disappears, and throws out its contents
on a free surface. Now, it will be perceived, that before
a cell can perform its functions as a nutritive cell, or as a
secreting cell, it must have acted as an absorbing cell.
This absorption, too, must necessarily be of a peculiar and
specific nature. It is in virtue of it that the nutritive cell
selects and absorbs from the liquor sanguinis those parts
of the latter necessary for building up the peculiar texture
of which the cell is the germ. It is in virtue of this pecu-
liar force that the secreting cell not only selects and
absorbs, but also in some instances elaborates, from the same
common material, the particular secretion of which it is
the immediate organ. And it is by the same force that
the cell becomes the immediate agent of absorption in certain
morbid processes.
"Absorption,"* says Professor Mtiller, " seems to depend
on an attraction, the nature of which is at present unknown,
but of which the very counterpart, as it were, takes place in
secretion ; the fluids altered by the secreting action being im-
pelled towards the free surface only of the secreting mem-
branes, and then pressed onwards by the successive portions
of fluid secreted. In many organs, for instance in those in-
vested with mucous membranes absorption by the lymphatics
and secretion by the secreting organs, are going on at the
same time on the same surface." It appears, however, from
what is stated in the present chapter, and in the Trans. Roy.
* Miiller's Physiology, page 30 Baly's Translation.
398 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
Soc. Edin., * that Professor Miiller, and indeed all the physio-
logists hitherto, have been in error in supposing the forces of
secretion and absorption as of different and opposite tendencies
the one attractive, the other repulsive. They are both
attractive, absorption being but the first stage in the process
of secretion. Secretion, in fact, differs from absorption, not
physiologically, but morphologically.
What has been stated in the present paper explains also
how, in the mucous membranes, " absorption by lymphatics
and secretion by secreting organs are going on at the same
time on the same surface." There is no physiological mystery
in this. It depends on a morphological circumstance. The
absorbing chyle-cells are on the attached surface of the ger-
minal membrane the secreting epithelia are on its free sur-
face ; the former are interstitial cells the latter peripheral ;
the former cast their contents into the substance of the
organism the latter into the surrounding medium.
The primitive cell, then, is primarily an organ of specific
absorption, and secondarily of nutrition, growth, and secretion.
As the chyme begins to pass along the small intestine, an
increased quantity of blood circulates in the capillaries of the
gut. In consequence of this increased flow of blood, or from
some other cause with which I am not yet acquainted, the
internal surface of the gut throws off its epithelium, which is
intermixed with the chyme in the cavity of the gut. The
cast-off epithelium is of two kinds that which covers the
villi, and which, from the duty it performs, may be named
protective epithelium, and that which lines the follicles, and
is endowed with secreting functions. The same action, then,
which, in removing the protective epithelia from the villi,
prepares the latter for their peculiar function of absorption,
throws out the secreting epithelia from the follicles, and thus
* Trails. Royal Society, Edin. 1842, "On the Secreting Structure, and
Laws of its Function." See also No. XXV. of this volume.
ON THE INTESTINAL VILLI. 399
conduces towards the performance of the function of these
follicles.
The villi, being now turgid with blood, erected, and naked,
are covered or coated by the whitish-grey matter already
described. This matter consists of chyme, of cast-off epithelia
of the villi, and of the secreting epithelia of the follicles. The
function of the villi now commences. The minute vesicles
which are interspersed among the terminal loops of the lacteals
of the villus, increase in size by drawing materials from the
blood through the coats of the capillary vessels, which ramify
at this spot in great abundance. While this increase in their
capacity is in progress, the growing vesicles are continually
exerting their absorbing function, and draw into their cavities
that portion of the chyme in the gut necessary to supply
materials for the chyle. When the vesicles respectively
attain in succession their specific size, they burst or dissolve,
their contents being cast into the texture of the villus, as in
the case of any other species of interstitial cell.
The debris, and the contents of the dissolved chyle-cells,
as well as the other matters which have already subserved
the nutrition of the villus, pass into the looped network of
lacteals, which, like other lymphatics, are continually em-
ployed in this peculiar function. As long as the cavity of
the gut contains chyme, the vesicles of the terminal extremity
of the villi continue to develope, to absorb chyle, and to
burst, and their remains and contents to be removed along
the lacteals.
When the gut contains no more chyme, the flow of blood
to the mucous membrane diminishes, the development of
new vesicles ceases, the lacteals empty themselves, and the
villi become flaccid.
The function of the villi now ceases till they are again
roused into action by another flow of chyme along the gut.
During the intervals of absorption, it becomes necessary
400 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
to protect the delicate villi from the matters contained in the
bowel. They had thrown off their protective epithelium
when required to perform their functions, just as the stomach
had done to afford gastric juice, and the intestinal follicles to
supply their peculiar secretions. In the intervals of diges-
tion the epithelium is rapidly reproduced.
The germinal membrane, which, as I have stated, not
only forms the outer membrane of the follicles, under the
epithelia, but also the underlying membrane of the villi,
contains in its substance germinal centres of an oval form,
situated at pretty regular distances. From these the epithe-
lium appears to be reproduced during the intervals of absorp-
tion, as stated in the first chapter.
During this process of development, the primary mem-
brane appears to split into two laminae, the epithelia passing
out from its nuclei between these. This would account for
the epithelia, particularly the prismatic and conical, adhering
by their free extremities.
Such are the processes which would appear to take place
in the villi of the intestinal tube during digestion and absorp-
tion. When considered in relation to the functions of digestion
and absorption of chyle, these processes are highly interesting.
The labours of the chemist have now so far simplified the
theory of digestion, as to deprive the stomach of the vitalis-
ing or organising powers so long ascribed to it.
Every step in this chemico-physiological inquiry leads to
the conclusion, that the changes which the food undergoes
while in the cavity of the gut are entirely of a chemical
nature.
If we continue, then, to apply the term digestion to that
series of processes by which the aliment is assimilated to the
matter of which the body is composed, we must divide the
series into two groups. The first group will include all those
changes which take place within the digestive tube, but ex-
ON THE INTESTINAL VILLT. 401
terior to the organism. The second will include those which
present themselves after the alimentary matter is taken up
into the animal body, and becomes buried in its substance.
The first group of processes are mechanical and chemical in
their nature. They may be considered in a great measure as
peculiar to the animal, although even vegetables throw out
from their roots matter which, acting on some of the materials
of the surrounding soil, prepares these for absorption.
The second group of processes is common to animals and
vegetables. In these, for the first time, are alimentary sub-
stances taken into the tissues of the organism. In animals,
as in plants, as I have already pointed out, these alimentary
substances are drawn by a peculiar force into the interior of
the cells, after escaping from which they pass on by the ab-
sorbent system. The chemist has not yet informed us of the
change which the matter has undergone during its passage
from the cavity of the gut, or from the soil, into the afferent
lacteals and the sap-vessels ; but if in vegetables, as in
animals, this matter passes into the cavities of the cells of
the spongiole before it passes on to the sap-vessels, then it is
highly probable that the organising and vitalising part of the
function of digestion commences in the cells of the spongiole
and of the extremity of the villus.
The extremity of the fibril of the root of a plant elongates
by the cells added to its tissue by the germinating spongiole.
The spongiole is, therefore, an active organ of growth as well
as of absorption. It is to the fibril of the root, what I have
denominated in the animal tissues the nutritive centre. I
conceive it to be probable, therefore, although as to this I
have made no observations, that absorption by, and elongation
of, the fibril of the root, vary inversely as one another. This
supposition is founded on the assumption that the cells of the
spongiole do not absorb by transmission, but by growth and
solution.
2o
402 ANATOMICAL AND PATHOLOGICAL OBSEKVATION S.
In the villi of the intestines of animals, my own obser-
vations lead me to believe that absorption by growth and
solution is the process which actually takes place.
The vesicular extremity, like the spongiole of the root-
fibril, is the primitive nutritive centre of the villus. The
villus originates in a cell. During the development of the
villus, this spot or cell was employed only in procuring
materials for the growth of the organ. In the perfect animal
the formative function of the spot ceases ; its action becomes
periodical, active during digestion, at rest during the intervals
of that process. The same function is performed, the same
force is in action, and the same organ, the cell, is provided
for absorption of alimentary matters in the embryo and in
the adult, in the plant and in the animal. The spongioles
of the root, the vesicles of the villus, the last layer of cells on
the internal membrane of the included yelk, or the cells
which cover the vasa lutea of the dependent yelk, and the
cells which cover the tufts of the placenta, are the parts of the
organism in which the alimentary matters first form a part of
that organism, and undergo the first steps of the organising
process.
ABSORPTION AND ULCERATION. 403
XXIII ABSOEPTION, ULCEEATION, AND THE
STKUCTUEES ENGAGED IN THESE PEOCESSES.
EVERY organic cell, the most simple as well as the most
complicated, when a separate organism, or when a part of a
more highly organised being, existing as a mere magazine of
matter, or performing some of the more striking of the vital
functions, invariably exhibits a phenomenon which is ante-
cedent to all others absorption from without of materials
for its own growth.
The various kinds of cells in any organism differ from one
another in this respect, that they have the power, each after
its kind, of selecting and procuring from the circulating
medium, or from other sources, the sort of matter necessary
for their own growth : or they have the power of elaborating,
or of conducing to the chemical change of the matter which
is absorbed by them. In this respect, the component cells of
animals and vegetables resemble the various species of beings
of which they form parts : they have not only the power of
selecting food, but the various species out of the same kind
of food are formed of matter and of parts which are specifically
different.
A most important circumstance in the history of cellular
phenomena is the duration of existence of a cell. Like the
various species of animals and vegetables, each species of cell
has its own average term of existence, each after its kind.
This average term is nevertheless contingent on the amount
of action which each species may, by peculiar circumstances
404 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
in the organism to which it belongs, be called on to perform.
This variableness in the average age of each species of cell, is
dependent on those circumstances which have been named
" nervous agency," " peculiarity of constitution," " irritability
of the parts," " morbid action," but may be studied independ-
ently of these agencies. The variableness in the term of ex-
istence of cells can no more be explained at present, than the
variety in the duration of the lives of species of animals and
vegetables : but the fact being known, its laws ascertained
will afford a clue to the explanation of many organic pheno-
mena and processes.
In the study of absorption, nutrition, and secretion,
attention has been directed to the vessels, as the active agents
in the performance of these processes. It is only a short
time since we have been willing to admit that the new
matter which is constantly replacing the old materials of the
frame, is selected and laid down, not by the ultimate vessels,
but by the non-vascular portions of the textures. It is only
now that we are beginning to know that secretion differs
from nutrition in its anatomical relations, and not in its
intimate nature. We still, however, retain in full force the
old belief in the active absorbent powers of the vessels, and
in the agency of the capillary and lymphatic vessels in re-
moving parts and modelling the forms.
It is not my intention to question entirely the active
agency of the veins and lymphatics in absorption and
ulceration, but merely to direct attention to the subject ; and
to point out, in some of the following chapters, a few organic
processes in which these actions appear to be functions in-
dependent of the vessels, the latter to be passive agents, mere
ducts for conveying away the products of action.
A rapidly-extending ulcerated surface appears as if the
textures were scooped out by a sharp instrument. The
textures are separated from the external medium by a thin
ABSORPTION AND ULCERATION. 405
film. This film is cellular in its constitution, and so far it is
analogous to the epidermis or epithelium. It is a peculiarly
endowed cellular layer, which takes up progressively the
place of the subjacent textures these being prepared for
dissolution, either by the state of the system, the condition
of the part, or by some influence induced by the contiguity
of the new formation. Carrying out, therefore, the principles
at present regarded as regulating the reciprocal functions of
textures and vessels, the subjacent textures disappear in con-
sequence of a disturbance of their own forces, consequent
upon the appearance of new forces residing in the cellular
layer. The disturbance and gradual annihilation of the
natural forces residing in the subjacent textures, is indicated
by the gradual disappearance of these. That new forces, not
formerly existing in the part, are developed, appears from the
formation of the cells of the cellular layer. As these appear
in rapid succession, and disappear as rapidly, the subjacent
textures also disappear, either by previous solution and
subsequent absorption by the properties and powers of the
former \ or under the peculiar circumstances of inflam-
matory action by the more vigorous growth of the former,
monopolising the resources of the part, the latter dissolving
and disappearing by the usual channels of the returning
circulation, more rapidly, but according to ordinary laws.
From this view of the process, it appears that, so far from
consisting in a diminution of the formative powers of the
part, such a progressive ulceration is actually an increase of
it. The apparent diminution is a consequence of the ex-
tremely limited duration of existence of the cells of the
absorbent layer, which die as rapidly as they are formed, dis-
appearing after dissolution, partly as a discharge from the
surface, but principally through the natural channels by which
the debris of parts, which have already performed their allotted
functions are taken up into the organism.
406 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
When a portion of dead or dying bone is about to be
separated from the living, the process which occurs is essen-
tially the same as that which has now been described. The
Haversian canals, which immediately bound the dead or dying
bone, are enlarged contemporaneously with the filling of their
cavities with a cellular growth. As this proceeds, contiguous
canals are thrown into one another. At last the dead or
dying bone is connected to the living by the cellular mass
alone. It is now loose, and has become so in consequence of
the cellular layer which surrounds it presenting a free surface
and throwing off pus.
In this process the veins and absorbents act on the osseous
texture of the walls of the Haversian canals in no otherwise
than in the natural state of the part. They are mediate, not
immediate, instruments of absorption. It is the cells of the
newly-formed cellular mass, contained in the Haversian canals,
which are the immediate cause of the removal of the bone,
either by taking it up as nourishment, and substituting them-
selves in its stead the bone being prepared for this absorp-
tion in a manner analogous to that which occurs in the
digestion of food previously to absorption of it by the cells of
the gut ;* or by the active formation of the cells of the new
substance monopolising the resources of the part, and so in-
ducing the disappearance of the osseous texture by the natural
channels of the returning circulation.
The process by which a slough in the soft parts is separated
from the living textures is similar to that which occurs in
bone.
In this view of ulceration, there is substituted for the
hypothetical active or aggressive power of absorption ascribed
to the veins and the lymphatics, a power which is known
* "Hence, the digestive process, instead of being confined to the stomach
and duodenum, is actually carried on without intermission, in all parts of a
living animal body. " Prout's Bridgewater Treatise, page 534.
ABSORPTION AND ULCERATION. 407
to exist in the organic cell during the progress of its growth ;
and the ultimate removal of the matter from the scene of
action is ascribed, partly to the formation of discharge, partly
to the yet unexplained, but at the same time undoubted, and
in all probability passive, agency of the returning circulation.
408 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
XXIV. THE PEOCESS OF ULCEEATION IN
AKTICULAE CAETILAGES. (PLATE IV.)
THE question as to the vascularity of cartilages cannot now
excite much interest, when we know that all the textures are
in themselves destitute of bloodvessels, which are accessory
parts, carriers of nourishment, not active agents in its
deposition. We do not consider cartilage as a texture into
which no bloodvessels pass, but only as less vascular than
some of the others. In a large mass of cartilage, as in those
of the bulky mammals, or in the thick cartilages of the foetal
skeleton, canals containing bloodvessels are found here and
there ; but in the thin articular cartilages of the adult human
subject few or no vessels can be detected.
It is evident, therefore, that in the process of ulceration
in cartilage, it cannot be the usual bloodvessels of the part
which are the- active agents.* Still less likely is it that
lymphatics, the existence of which has never been asserted in
this texture, are the absorbing instruments.
If a thin section, at right angles, be made through the
articular cartilage of a joint, at any part where it is covered
by gelatinous membrane in scrofulous disease, or by false
membrane in simple inflammatory condition of the joint, and
'if this section be examined, it will be found to present the
following appearances.
* See Mr. Aston Key's Paper in the London Med. Chir. Trans, vol. xviii.
Part I., "On the Ulcerative Process in Joints."
ULCERATION IN ARTICULAR CARTILAGES. 409
On one edge of the section is the cartilage unaltered, with
its corpuscles natural in position and size. On the opposite
edge, is the gelatinous, or false membrane, both consisting
essentially of nucleated particles, intermixed, especially in the
latter, with fibres and bloodvessels ; and, in the former, with
tubercular granular matter. In the immediate vicinity, and
on both sides of the irregular edge of the section of cartilage,
where it is connected to the membrane, certain remarkable
appearances are seen. These consist, on the side of the
cartilage, of a change in the shape and size of the cartilage-
corpuscles. Instead of being of their usual form, they are
larger, rounded, or oviform ; and, instead of two or three
nucleated cells in their interior, contain a mass of them. At
the very edge of the ulcerated cartilage, the cellular contents
of the enlarged cartilage-corpuscles communicate with the
diseased membrane by openings more or less extended.
Some of the ovoidal masses in the enlarged corpuscles may
be seen half-released from their cavities by the removal of the
cartilage ; and others of them may be observed in the sub-
stance of the false membrane, close to the cartilage, where
they have been left by the entire removal of the cartilage
which originally surrounded them.
If a portion of the false membrane be gradually torn off
the cartilage, the latter will appear rough and honey-combed.
Into each depression on its surface a nipple-like projection
of the false membrane penetrates. The cavities of the en-
larged corpuscles of the cartilage open on the ulcerated
surface by orifices of a size proportional to the extent of
absorption of the walls of the corpuscle, and of the free
surface of the cartilage.
The texture of the cartilage does not exhibit, during the
progress of the ulceration, any trace of vascularity. The
false membrane is vascular, and loops of capillary vessels dip
into the substance of the nipple-like projections which fill the
410 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. .
depressions on the ulcerated surface of the cartilage ;* but,
with the exception of the enlargement of the corpuscules, and
the peculiar development of their contents, no change has
occurred in it. A layer of nucleated particles always exists
between the loops of capillaries and the ulcerated surface.
The cartilage, where it is not covered by the false mem-
brane, is unchanged in structure. The membrane generally
adheres with some firmness to the ulcerating surface ; in other
instances it is loosely applied to it ; but in all, the latter is
accurately moulded to the former.
In scrofulous disease of the cancellated texture of the
heads of bones, or in cases where the joint only is affected,
but to the extent of total destruction of the cartilage over part
or the whole of its extent, the latter is, during the progress of
the ulceration, attacked from its attached surface. Nipple-
shaped processes of vascular cellular texture pass from the
bone into the attached surface of the cartilage, the latter
undergoing the change already described. The processes from
the two surfaces may thus meet half-way in the substance of
the cartilage, or they may pass from the attached, and project
through a sound portion of the surface of the cartilage, like
little vascular nipples or granulations. The cartilage may
thus be riddled, or it may be broken up into scales of varying
size and thickness, or it may be undermined for a greater or
less extent, or be thrown into the fluid of the cavity of the
joint in small detached portions, or it may entirely disappear.
On the principles already laid down, if absorbents exist, as
we have reason to believe they do in the false membrane,
neither they nor the veins are to be considered as the active
or immediate agents in the absorption of the cartilage. They
certainly are not so in the absorption of the walls of the cor-
* The vascular loops described and figured by Mr. Liston are not vessels
in the cartilage, but the vessels described in the text. LISTON. Lond. Med.
Chir. Trans.
ULCERATION IN ARTICULAR CARTILAGES. 411
puscules, and this, as well as the analogy of similar processes,
gives weight to the opinion to which I have come, that they
are not the immediate instruments in the absorption of the
free surface. The cells of new formation appear to be the
immediate agents in this action. They absorb into their
substance the hyaline matter of the cartilage, the latter pro-
bably not being removed at once from the spot, but merely
converted into soft cellular texture ; the process being one of
transformation rather than removal.
412 ANATOMICAL AND PATHOLOGICAL OBSEHVATIONS.
XXV. SECKETING STKUCTUKES. (PLATES IV. V)
MALPIGHI was the first to announce that all secreting glands
are essentially composed of tubes, with blind extremities.*
Mliller, by his laborious researches, has brought this depart-
ment of the anatomy of glands to its present comparatively
perfect condition.! Purkinje announced his hypothesis of the
secreting function of the nucleated epithelium of the gland-
ducts, but made no statement to show that he had verified it
by observation^ Schwann suggested that the epithelium of
the mucous membranes might be the secreting organ of these
surfaces.^ Henle described minutely the epithelium-cells
which line the ducts of the principal glands and follicles, but
did not prove that these are the secreting organs. The same
anatomist has stated that the terminal extremities of certain
gland-ducts are closed vesicles, within which the secretion is
formed, and which contain nucleated cells. Henle has not,
therefore, verified the hypothesis of Purkinje, although he is
correct in stating that the terminal vesicles of certain gland-
ducts are closed.|| It will be shown, that the secretion is not
formed, as Henle has asserted, in the closed vesicles, but in
the nucleated cells themselves.
The discrepant observation of BoehmlF and Krause** on
the glands of Peyer, were in some measure reconciled by
* Exercitationes dc Structura Viscerum, 1665.
t J. Miiller, De Gland. Struct. Penit. 1830. $ Isis, 1838.
Froriep. Notiz. 1838. || Miiller's Archiv, 1838, 1839.
U De Gland. Intestin. Struct. Penit. 1835. ** Mailer's A rchir, 1837.
Plate V
J. O-ooatftrjJc
SECRETING STRUCTURES. 413
Henle, who referred them to the same class of structures as
the closed vesicular extremities of the ducts of compound
glands. Dr. Allen Thomson has observed, that the primitive
condition of the gastric and intestinal gland is a closed vesicle.*
Wasmann described the structure of the gastric glands in the
pig ; and his description will be fully explained by the
following observations and views.-)- Hallman has given a
detailed account of the testicle of the ray,;]; which closely re-
sembles that of the Sgualus cornubicus, as described in another
part of this chapter. None of the recent observations on the
development of the spermatozoa have proved that the
vesicles, in which they are formed, are the epithelium -cells
of the ducts of the testicle. I am indebted to Dr. Allen
Thomson for directing my attention to a notice in Valentin's
Repertorium, 1841, of a Dissertation by Erdl, in which he
describes, in the kidney of that mollusc, cells, the nuclei of
which pass out by the duct of the gland. It does not appear,
however, that Erdl had discovered the uric acid within the
celL||
If the membrane which lines the secreting portion of the
internal surface of the ink-bag of Loligo sagittata (Lam ark) be
carefully freed from adhering secretion by washing, it will be
found to consist almost entirely of nucleated cells, of a dark-
brown or black colour. These cells are spherical or ovoidal.
. Their nuclei consist of cells, grouped together in a mass. Be-
tween these composite nuclei, and the walls of their containing
cells, is a fluid of a dark-brown colour. This fluid resembles,
in every respect, the secretion of the ink-bag itself. It
* Proceedings of the British Association, 1840.
f De Digestions Nonnulla, Diss. manq. Berol. 1839.
J Miiller's Archiv, 1840.
De Helicis Algirce vasis sanguiferis, 1840.
|| Mr. Bowman lias shown that the fat in the fatty liver is contained in the
secreting cells. Observations on the Minute Structure of the Fatty Degenera-
tion of the Liver, January 1842.
414 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
renders each cell prominent and turgid, and is the cause of its
dark colour.
The dilated terminal extremities of the ducts in the liver
of Helix aspersa (Mliller) contain a mass of cells. If one of
these cells be isolated and examined, it presents a nucleus
consisting of one or more cells. Between the nucleus and the
wall of the containing cell is a fluid of an amber tint, and
floating in this fluid are a few oil-globules. This fluid differs
in no respect from the bile, as found in the ducts of the
gland.
If a portion of the ramified glandular organ which opens
into the fundus of the stomach of Uraster rubens (Agassiz) be
examined, its internal surface is found to be lined with cells ;
between the nucleus of each of which and the wall of the cell
itself a dark-brown fluid is situated. The organ secretes a
fluid, supposed to be of the nature of bile.
The dark-brown ramified cseca of the same animal exhibit
on their internal surfaces an arrangement of nucleated cells,
the cavities of which contain a brown fluid. These caeca are
also supposed to perform, or to assist in the performance of,
the function of the liver.
The liver of Modiola vulgaris (Fleming) contains masses of
spherical cells. Between the nucleus and the wall of each of
these cells a light-brown fluid is situated, bearing a close re-
semblance to the bile in the gastro-hepatic pouches.
The nucleated cells which are arranged around the gastro-
hepatic pouches of the Pecten opercularis are irregular in
shape, and distended with a fluid resembling the bile.
The hepatic organ, which is situated in the loop of
intestine of Pirena prunum (Fleming), consists of a mass of
nucleated cells. These cells are collected in groups, in the
interior of larger cells or vesicles. These nucleated cells are
filled with a light-brown bilious fluid.
The hepatic organ, situated in the midst of the reproductive
SECRETING STRUCTURES. 415
apparatus, and in the loop of the intestine of Phallmia
vulgaris (Forbes and Goodsir), consists of a number of vesicles,
and each vesicle contains a mass of nucleated cells. These
cells contain a dark-brown bilious fluid.
The hepatic organ in the neighbourhood of the stomach,
in each of the individuals of the compound mollusc, the
Alpidium ficus (Linnaeus), consists of nucleated cells, which
contain in their cavities a reddish-brown fluid.
The liver of Loligo sagittata (Lamark) contains a number
of nucleated cells, ovoidal and kidney-shaped. These cells
are distended with a brown bilious fluid.
The nucleated cells in the liver of Aplysia punctata
(Cuvier) are full of a dark-brown fluid.
The ultimate vesicular caeca of the liver of Buccinum
undatum contain ovoidal vesicles of various sizes. These
vesicles contain more or less numerous nucleated cells. The
cells are full of a dark-brown fluid.
The hepatic caeca in the liver of Patella vulgata. Each of
these vesicles encloses a body, which consists of a number of
nucleated cells, full of a dark fluid resembling the bile.
The simple biliary apparatus which surrounds the gastric
portion of the intestinal tube of Nereis contains nucleated
cells, full of a light-brown fluid.
The hepatic caeca of Carcinus mcenas contains cells full of
a fluid of an ochrey colour, along with numerous oil-globules.
The hepatic eseca of Carabus catenulatus (Fabricius) contain
cells attached to their internal surfaces. Between the nuclei
and the cell -walls a brown liquid containing numerous
granules is situated.
The kidney of Helix aspersa (Mliller) is principally com-
posed of numerous transparent vesicles. In the centre of
each vesicle is situated a cell full of a dead white granular
mass. This gland secretes pure uric acid.
The ultimate elements of the human liver are nucleated
416 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
cells. Between the nucleus and the cell-wall is a light-brown
fluid, with one or two oil-globules floating in it.
The vesicular caeca in the testicle of Sgualus cornubicus
contain nucleated cells, which ultimately exhibit in their
interior bundles of spermatozoa.
The generative caeca of Echiurus mdgaris (Lamark) contain
cells full of minute spermatozoa.
Aplysia punctata secretes from the edge and internal
surface of its mantle a quantity of purple fluid. The secreting
surface of the mantle consists of an arrangement of spherical
nucleated cells. These cells are distended with a dark purple
matter.
The edge and internal surface of the mantle of Janthina
fragilis (Lamark), the animal which supplied the Tyrian dye,
secretes a deep bluish purple fluid. The secreting surface
consists of a layer of nucleated cells, distended with a dark
purple matter.
If an ultimate acinus of the mammary gland of the bitch
be examined during lactation, it is seen to contain a mass of
nucleated cells. These cells are generally ovoidal, and rather
transparent. Between the nucleus and the cell-wall of each
a quantity of fluid is contained, and in this fluid float one,
two, three, or more oil-like globules, exactly resembling those
of the milk.
In addition to the series of examples already given, 1
might adduce many others to prove that secretion is a function
of the nucleated cell. Some secretions, indeed, are so trans-
parent and colourless, as to render ocular proof of their
original formation within cells impossible ; and we are not
yet in possession of chemical tests sufficiently delicate for the
detection of such minute quantities. The examples I have
selected, however, show that the most important and most
striking secretions are formed in this manner. The proof of
the universality of the fact, in reference to the glandular
SECRETING STRUCTURES. 41*7
structures which produce colourless secretions, can only rest
at present on the identity of the anatomical changes which
occur in their cellular elements. This part of the proof I shall
enter upon in another part of this chapter.
The secretion within a primitive cell is always situated
between the nucleus and the cell-wall, and would appear to
be a product of the nucleus.*
The ultimate secreting structure, then, is the primitive
cell, endowed with a peculiar organic agency, according to the
secretion it is destined to produce. I shall henceforward
name it the primary secreting cell. It consists, like other
primitive cells, of three parts the nucleus, the cell-wall, and
the cavity. The nucleus is its generative organ, and may or
may not, according to circumstances, become developed into
young cells. The cavity is the receptacle in which the
secretion is retained till the quantity has reached its proper
limit, and till the period has arrived for its discharge.
Each primary secreting cell is endowed with its own
peculiar property, according to the organ in which it is
situated. In the liver it secretes bile in the mamma, milk,
etc.
The primary secreting cells of some glands have merely
to separate from the nutritive medium a greater or less
number of matters already existing in it. Other primary
secreting cells are endowed with the more exalted property
of elaborating from the nutritive medium matters which do
not exist in it.
* In the original Memoir the cell-wall is stated to "be the probable secreting
structure. "Now, as we know that the nucleus is the reproductive organ of
the cell that it is from it, as from a germinal spot, that new cells are formed
I am inclined to believe that it has nothing to do with the formation of the
secretion. I believe that the cell-wall itself is the structure, by the organic
action of which each cell becomes distended with its peculiar secretion, at the
expense of the ordinary nutritive medium which surrounds it." Trans. Roy.
Soc. Edin. 1842.
2E
418 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
The discovery of the secreting agency of the primitive cell
does not remove the principal mystery in which this function
has always been involved. One cell secretes bile, another
milk ; yet the one cell does not differ more in structure from
the other than the lining membrane of the duct of one gland
from the lining membrane of the duct of another. The
general fact, however, that the primitive cell is the ultimate
secreting structure, is of great value in physiological science,
inasmuch as it connects secretion with growth, as phenomena
regulated by the same laws. The force, of whatever kind it
may be, which enables one primary formative cell to produce
nerve and another muscle, by an arrangement within itself of
the common materials of nutrition, is identical with that force
which enables one primary secreting cell to distend itself
with bile, and another with milk.
Instead of growth being a species of imbibing force, and
secretion on the contrary a repulsive the one centripetal,
the other centrifugal they are both centripetal. Even in
their later stages the two processes, growth and secretion, do
not differ. The primary formative cell, after becoming
distended with its peculiar nutritive matter, in some instances
changes its form according to certain laws, and then, after a
longer or shorter period, dissolves and disappears in the inter-
cellular space in which it is situated, its materials passing
into the circulating system if it be an internal, and being
merely thrown off if it be an external cell. The primary
secreting cell, again, after distension with its secretion, does
not change its form so much as certain of the formative cells,
but the subsequent stages are identical with those of the latter.
It bursts or dissolves, and throws out its contents either into
ducts or gland-cavities, both of which, as I shall afterwards
show, are intercellular spaces, or from the free surface of the
body.
The general fact of every secretion being formed within
SECRETING STRUCTURES. 419
cells, explains a difficulty which has hitherto puzzled physio-
logists viz. why a secretion should only be poured out on the
free surface of a gland-duct or secreting membrane.
"Why," says Professor Miiller, "does not the mucus
collect as readily between the coats of the intestine as exude
from the inner surface ? Why does not the bile permeate the
walls of the biliary ducts, and escape on the surface of the
liver, as readily as it forces its way outwards in the course of
the ducts ? Why does the semen collect on the inner surface
only of the tubuli seminiferi, and not on their exterior, in
their interstices? The elimination of the secreted fluid on
one side only of the secreting membrane viz. on the interior
of the canals is one of the greatest enigmas in physiology."
Mliller proceeds to explain this enigma by certain hypotheses ;
but the difficulty disappears, the mystery is removed, when
we know that the secretion only exists in the interior of the
ripe cells of the free surface of the ducts or membrane, and is
poured out or eliminated simply by the bursting and solution
of these superficial cells.
I have hitherto confined my observations to the structure
and function of the ultimate secreting element, the primary
secreting cell. I now proceed to state the laws which I have
observed to regulate the original formation, the development,
and the disappearance of the primary organ. This subject
necessarily involves the description of the various minute
arrangements of glands and other secreting structures.
If the testicle of Squalus cornubicus (Gmelin) be examined
when the animal is in a state of sexual vigour, the following
arrangements of structure present themselves :
The gland consists of a number of lobes separated, and at
the same time connected, by a web of filamentous texture, in
which ramify the principal bloodvessels.
The lobes, when freed from this tunic, present on their
surface a number of vesicles. When the gland is dissected
420 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
under water, and one of the lobes is raised out of its capsule,
an extremely delicate duct is observed to pass from it into
the substance of the capsule, to join the ducts of the other
lobes.
When a section is made through one of the lobes, it be-
comes evident that the vesicles are situated principally on its
exterior.
If a small portion be macerated in water for a few hours,
and dissected with a couple of needles, there are observed
attached to the delicate ducts which ramify through the lobe
vesicles in all stages of development. These stages are
the following : 1st, A single nucleated cell attached to
the side of the duct, and protruding, as it were, its outer
membrane.
2d, A cell containing a few young cells grouped in a mass
within it ; the parent cell presenting itself more prominently
on the side of the duct.
3d, A cell attached by a pedicle to the duct, the pedicle
being tubular, and communicating with the duct ; the cell
itself being pyriform, but closed and full of nucleated cells.
Ath, Cells larger than the last, assuming more of a globular
form, still closed, full of nucleated cells, and situated more
towards the surface of the lobe.
5th, The full-sized vesicles already described as situated
at the surface of the lobe. These vesicles are spherical, per-
fectly closed ; that part of the wall of each which is attached
to the hollow pedicle forms a diaphragm across the passage,
so that the vesicle has no communication with the ducts of the
gland. The contents of the vesicles are in various stages of
development. Those least advanced are full of simple nucle-
ated cells ; in others, the included cells contain young cells in
their interior, so that they appear granular under low powers ;
in others, the included cells have begun at a certain part of
the vesicle to elongate into cylinders, with slightly rounded
SECRETING STRUCTURES. 421
extremities. In others the cylindrical elongation has taken
place in all the included cells, with the exception of a few,
which still retain the rounded form, at a spot opposite to that
part of the vesicle in which the change commenced ; and at
the same time it may be observed, that the cylindrical cells
have become arranged in a spiral direction within the parent
vesicle. Lastly, Vesicles exist in which all the cells are
cylindrical, and are arranged within its cavity in a spiral
direction.
The changes which occur in the included nucleated cells
of the vesicle are highly interesting. After the nucleus of
each has become developed into a mass of cells, the parent
cell becomes, as has been stated, cylindrical. The change in
the shape of the cell is contemporaneous with the appearance
of a spiral arrangement of the included mass of cells. This
spiral arrangement is also contemporaneous with an elonga-
tion of each cell in the mass, in the direction of the axis of
the parent cell. When the elongation has reached its maxi-
mum, the original mass of included cells has assumed the
appearance of a bunch of spirals, like corkscrews arranged
one with another, spiral to spiral. In particular lights the
cylindrical cell presents alternate spots of light and shade,
but by management of the illumination, the included spiral
filaments become evident ; the light and shade are seen to
arise from the alternate convexities and concavities of the
spiral filaments, combined in a spiral bundle.
In vesicles more advanced, the wall of the cylindrical cells
has become attenuated.
In other vesicles the diaphragms across their necks have
dissolved or burst, the bundles of spiral filaments float along
the ducts of the gland, or separate into individual spiral fila-
ments. These filaments are completely developed spermatozoa,
pointed and filamentous at both extremities, thicker and
spiral in the middle.
422 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
In the centre of the lobe, where the smaller ducts meet to
form the principal duct, there is a mass of grey gelatinous
matter through which the ducts pass. This gelatinous matter
consists of a number of cells lying between the converging
ducts, and from their peculiar appearance not presenting the
usual nuclei. I am inclined to believe that they are either
vesicles which have never become developed on account of the
pressure of the surrounding parts, or that they are old vesicles
in a state of atrophy after the expulsion of their contents.
Having now described the changes which are constantly
taking place in the testicle of this shark when the organ is in
a state of functional activity, I must defer till a future occa-
sion an account of similar changes which occur in the paren-
chyma of an order of glands, of which the one already
described may be considered as a type. I may state, how-
ever, that I have ascertained the following general facts in
reference to glands of this order :
1st, The glandular parenchyma is in a constant state of
change, passing through stages of development, maturity, and
atrophy.
2d, The state of change is contemporaneous with, and
proportional to, the formation of the secretion, being rapid
when the latter is profuse, and vice versa.
3d, There are not, as has hitherto been supposed, two
vital processes going on at the same time in the gland, growth
and secretion, but only one viz. growth. The only difference
between this kind of growth and that which occurs in other
organs being, that a portion of the product is, from the
anatomical condition of the part, thrown out of the system.
4:th, The vital formative process which goes on in a gland
is regulated by the anatomical laws of other primitive cellular
parts.
5th, An acinus is at first a single nucleated cell. From
the nucleus of this cell others are produced. From these,
SECRETING STRUCTURES. 423
again, others rise in the same manner. The parent cell,
however, does not dissolve away, but remains as a covering to
the whole mass, and is appended to the extremity of the duct.
Its cavity, therefore, as a consequence of its mode of develop-
ment, has no communication with the duct.
The original parent cell now begins to dissolve away, or
to burst into the duct at a period when its contents have
attained their full maturity. This period varies in different
glands, according to a law or laws peculiar to each of them.
6th, In the gland there are a number of points from which
acini are developed, as from so many centres. These I name
the germinal spots of the gland.
7th, The secretion of a gland is not the product of the
parent cell of the acinus, but of its included mass of cells.
The parent cell or vesicle may be denominated the primary
cell ; its included nucleated cells, after they have become
primary secreting cells, may be named secondary cells of the
acinus.
8th, There are three orders of secretions : (1.) A true secre-
tion that is, matter formed in the primary secreting cell-
cavities ; or, (2.) A mixture of a fluid formed in these cell-
cavities with the developed or undeveloped nuclei of the cells
themselves ; and, (3.) It may be a number of secondary cells
passing out entire.
In the liver of Carcinus mcenas, and other Crustacea, it
may be observed, that each of the follicles of which it consists
presents the following structure : The blind extremity of the
follicle is slightly pointed, and contains in its interior a mass
of perfectly transparent nucleated cells. From the blind ex-
tremity downwards, these cells appear in progressive states of
development. At first they are mere primitive nucleated cells ;
further on they contain young cells ; and beyond this they
assume the characters of primary secreting cells, being dis-
tended with yellow bile, in which float oil-globules, the oil in
424 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
some instances occupying the whole cell. Near the attached
extremity of the follicle an irregular passage exists in the
midst of the cells, and allows the contents of the cells which
bound it to pass on to the branches of the hepatic duct.
This arrangement of the secreting apparatus may be taken
as the type of an order of glands, which consist of follicles
more or less elongated. Growth in glands of this kind is
regulated by the following laws :
1st, Each follicle is virtually permanent, but actually in a
constant state of development and growth.
2d t This growth is contemporaneous with the function of
the gland, that function being merely a part of the growth,
and a consequence of the circumstances under which it occurs.
3d, Each follicle possesses a germinal spot situated at its
blind extremity.
4Jh, The vital action of some follicles is continuous, the
germinal spot in each never ceasing to develope nucleated
cells, which take on the action of and become primary
secreting cells, as they advance along the follicle. The action
of other follicles is periodical.
5th, The wall, or germinal membrane of the follicle, is
also in a state of progressive growth, acquiring additions to
its length at its blind extremity, and becoming absorbed at
its attached extremity. My brother, in a paper on the
' Development and Metamorphoses of Caligus" read in the
Wernerian Society, April 1842, has stated that the Avail of
the elongated and convoluted follicle, which constitutes the
ovary in that genus, grows from its blind to its free extremity,
at the same rate as the eggs advance in development and
position. A progressive growth of this kind would account
for the steady advance of its attached contents, and would
also place the wall of the follicle in the same category with
the primary vesicle, germinal membrane, or wall, of the acinus
in the vesicular glands.
SECRETING STRUCTURES. 425
6th, The primary secreting cells of the follicle are not
always isolated They are sometimes arranged in groups,
and when they are so each group is enclosed within its
parent cell, the group of cells advancing in development ac-
cording to its position in the follicle, but never exceeding a
particular size in each follicle.
In my original memoir, I stated my opinion that there is
an order of glands namely, those with very much elongated
ducts whicli do not possess germinal spots in particular
situations, but in which these spots are diffused more uni-
formly over the whole internal surface of the ducts. The
human kidney is a gland of this order.*
We require renewed observations on the original develop-
ment of glands in the embryo. From the information we
possess, however, it appears that the process is identical in
its nature with the growth of a gland during its state of
functional activity.
The blastema, which announces the approaching formation
of a gland in the embryo, in some instances precedes, and is
in other instances contemporaneous with, the conical blind
protrusion of the membrane upon the surface of which the
future gland is to pour its secretion.
In certain instances it has been observed that the smaller
branches of the duct are not formed by continued protrusion
of the original blind sac, but are hollowed out independently
in the substance of the blastema, and subsequently com-
municate with the ducts.
* " 1 am the more inclined to believe this, from what I have observed in
certain secreting membranes. Thus the membranes which secrete the purple
in Aplysia and Janthina are not covered with a continuous layer of purple
secreting cells ; but over the whole surface, and at regular distances, there are
spots, consisting of transparent, colourless, nucleated cells, around which the
neighbouring cells become coloured. Are these transparent cells the germinal
spots of these secreting membranes ? And may not the walls of the elongated
tubes, and the surfaces of the laminse within certain glands, have a similar
arrangement of germinal spots?" Trans. Roy. Soc. Edin. 1842.
426 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
It appears to be highly probable, therefore, that a gland
is originally a mass of nucleated cells, the progeny of one or
more parent cells ; that the membrane in connection with
the embryo gland may or may not, according to the case, send
a portion of the membrane, in the form of a hollow cone, into
the mass ; but whether this happens or not, the extremities
of the ducts are formed as closed vesicles, and then nucleated
cells are formed within them, and are the parents of the
epithelium cells of the perfect organ.
Dr. Allen Thomson has ascertained that the follicles of
the stomach and large intestine are originally closed vesicles.
This would appear to show that a nucleated cell is the original
form of a follicle, and the source of the germinal spot which
plays so important a part in its future actions.
The ducts of glands are, therefore, intercellular passages.
This is an important consideration, inasmuch as it ranges
them in the same category with the intercellular passages
and secreting receptacles of vegetables.*
Since the publication of my paper on the secreting struc-
tures, in the Transactions of the Eoyal Society of Edinburgh
in 1842, I have satisfied myself that I was in error in attri-
buting to the cell-wall the important function of separating
and preparing the secretion contained in the cell -cavity.
The nucleus is the part which effects this. The secretion con-
tained in the cavity of the cell appears to be the product of
the solution of successive developments of the nucleus, which
in some instances contains in its component vesicles the
peculiar secretion, as in the bile-cells of certain Mollusca, and
in others becomes developed into the secretion itself, as in
seminal cells. In every instance, the nucleus is directed
towards the source of nutritive matter, the cell- wall is opposed
to the cavity into which the secretion is cast. This accords
with that most important observation of Dr. Martin Barry, on
the function of the nucleus in cellular development.
* Henle, in his General Anatomy, has made a similar statement.
SECRETING STRUCTURES. 427
I have also had an opportunity of verifying, and to an
extent which I did not at the time fully anticipate, the re-
markable vital properties of the third order of secretions,
referred to in the memoir to which I have just alluded. The
distinctive character of secretions of the third order is, that
when thrown into the cavity of the gland, they consist of
entire cells, instead of being the result of the partial or entire
dissolution of the secreting cells. It is the most remarkable
peculiarity of this order of secretions that, after the secreting
cells have been separated from the gland, and cast into the
duct or cavity, and therefore no longer a component part of
the organism, they retain so much individuality of life, as to
proceed in their development to a greater or less extent in
their course along the canal or duct, before they arrive at
their full extent of elimination.
The most remarkable instance of this peculiarity of secre-
tions of this order, is that discovered by my brother, and
recorded by him in a succeeding chapter.* He has observed
that the seminal secretion of the decapodous crustaceans
undergoes successive developments in its progress down the
duct of the testis, but that it only becomes developed into
spermatozoa after coitus, and in the spermatheca of the female.
He has also ascertained that, apparently for the nourishment
of the component cells of a secretion of this kind, a quantity
of albuminous matter floats among them, by absorbing which
they derive materials for development after separation from
the walls of the gland.
This albuminous matter he compares to the substance
which, according to Dr. Martin Barry's researches, results
from the solution of certain cells of a brood, and affords
nourishment to their survivors. It is one of other instances
in which cells do not derive their nourishment from the blood,
but from parts in their neighbourhood which have undergone
* See page 429.
428 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
solution ; and it involves a principle which serves to explain
many processes in health and disease, some of which have been
referred to in other parts of this work.
I conclude, therefore, from the observations which I have
made 1st, That all the true secretions are formed or selected
by a vital action of the nucleated cell, and that they are first
contained in the cavity of that cell ; 2d, That growth and
secretion are identical the same vital process, under different
circumstances.*
* In Mr. Bowman's elaborate Paper "On the Structure and Use of the
Malpighian Bodies of the Kidney," read in the Koyal Society of London, 17th
February 1842, and in his Article " Mucous Membrane," in the Cydopcedia of
Anatomy, written in December 1841, certain parts of the theory of secretion
are well elucidated by a reference to human structure. In my own Memoir,
read in the Royal Society of Edinburgh, 30th March 1842, I endeavoured, by
an appeal to facts in comparative anatomy, to establish secretion as a function
of the nucleated cell, and to show that glandular phenomena are only the
changes which the cellular elements of these organs undergo. Mr. Bowman's
own observation on the secretion of fat by the cells of the human liver in a
state of disease was an important and positive result ; and Professor John
Reid, with whom I had frequent conversations on the subject of secretion, and
to whom I had communicated my views on the subject a year before the
publication of my Paper, was in the habit of supporting Purkinje and Schwann's
hypothesis, by an appeal to the structure of Molluscum contagiosum, as de-
scribed by Professor Henderson and Dr. Paterson in the Edinburgh Medical
and Surgical Journal, 1841.
VoLJI
Plate VII
TESTIS IN DECAPODOUS CRUSTACEA. 429
XXVI. THE TESTIS AND ITS SECKETION IN THE
DECAPODOUS CKUSTACEANS. (PLATES VII. VIII.)
THE organs of generation in the male crustacean consist of
testes, vasa deferentia, and external or intromittent organs.
In no class of animals do these parts vary so much as in
that now under consideration. In every family, and almost
in every genus, they afford generic, and in some even specific,
characters. This variableness of configuration and structure
is not peculiar to the organs of reproduction, but exists also
in the other systems the vascular and respiratory, the
nervous and locomotive. Such a variableness is to be looked
for in a class, the forms in which pass from that of the
annelids, through the articulata, to the mollusc. Through-
out all this range of form the organs and functions vary in
accordance with those in the group of animals to which the
crustaceans presenting them are analogous.
In all the higher, or Brachyurous Crustaceans, the internal
organs of generation are comparatively most highly developed.
These organs exhibit the greatest complexity of form and
structure among the Triangulares, but in the next order, the
Cyclometopa, they are of great size. These crustaceans are
accordingly the most prolific, and in' greatest demand as
articles of diet. The Catometopa, or rather the higher forms
of that family, have these organs also very large ; this family
containing the land-crabs of tropical climates, which are used
as food.
As we descend towards the Anomoura, the internal organs
of generation are found to give way gradually to others, which
430 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
have apparently a more important part to play in the economy ;
and in the lowest forms of the Oxystoma they are in a
minimum state of development.
In this division (Brachyura) they occupy both sides of the
shell, lying upon the liver, and sometimes entering the folds
of that organ, and separated with difficulty from it. In
others, as Cancer and Carcinus, when in an active state, they
completely cover and conceal the liver.
In Leptopodium and Hyas the testis is a body of consider-
able size, lying upon the upper surface of the liver, and con-
sisting of irregular masses, formed by the twistings of its
constituent duct It is covered by a delicate membrane,
which is much stronger on the body of the testis than else-
where, and is analogous to the tunica albuginea in the higher
animals. The gland, extending forward, gradually enlarges,
and when it has arrived in a line with the stomach, curves
slightly inwards to the mesial plane, and terminates in a large
tube on each side, which is its duct much dilated. This large
tube, making a number of convolutions, proceeds inwards and
downwards until it meets and forms a junction with that of
the opposite side. The anastomosis is incomplete in this
division of the class. After running in contact for some
distance, the two ducts again separate, and each becoming
much smaller, terminates by opening at the base of the ex-
ternal organs.
In the Anomoura, instead of being situated in the thorax,
as in the Brachyura, the testes are contained in the abdominal
segment of the body, lying on and above the liver. They are
very small in all the animals of this section, the tubuli
seminiferi being large, and after making a few convolutions
ending in the vas deferens, which opens on the base of the
fifth pair of legs, without the intervention of an intromittent
organ. The elongated acini are confined to the lower part,
and are contained within the external tunic of the gland.
PlatvVHI
TESTIS IN DECAPODOUS CRUSTACEA. 431-
Iii the Macroura the testes commence on each side of the
stomach, and extend down to the middle parts of the abdomen.
In almost all the species of the section, these organs are
narrow ribbon-shaped organs, connected with one another
immediately behind the stomach by a narrow commissure ;
the vasa deferentia come off behind this commissure, and are
more distinct than in any other of the sections. In GalatJiea
these organs are more complicated, the tube being more
convoluted.
The ultimate structure of the testis consists of a germinal
membrane, covered externally by the common tunic of the
organ, or by processes from it. The germinal membrane, in the
upper or first part of its course, developes from germinal spots
in its substance formative cells of a spherical shape and of
small size, which will be afterwards described. In the lower
part of the tube, the formative cells assume a peculiar linear
or spindle shape, attached by one of their extremities to the
germinal membrane, and projecting either into the cavity of
the gland-duct, as in Pagurus, or from its external surface as
in Crcdatlua, and therefore in this case covered by the common
enveloping tunic of the gland, or by processes of it which
correspond to the areolar vascular matrix of the glands in the
higher animals.
When the animal is getting into season, numerous small
cells are found, as just described, on the internal surface of
the seminal tube, and more particularly from that portion of
the gland which lies on the surface of the liver. As the
animal becomes stronger, these cells increase in size from the
formation of young in their interior. That these young or
secondary cells are produced from the germinal spots on the
germinal membrane of the seminal tube, from which the
primary cell took its origin, appeared highly probable, among
other circumstances from this, that after the latter had burst,
its cell- wall was smooth and regular, not broken up or rough,
432 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
as might have been expected, had the secondary cells been
formed from it. After these primary cells have burst, the
secondary cells contained in them pass down the seminal tube,
to undergo the changes to be afterwards described.
The spindle-shaped cells in the lower part of the seminal
tube are large primary cells, two or three generally arising
from a disc or spot in the germinal membrane. They corre-
spond in every respect, except in shape and size, to the
spherical primary cells further up the tube, and like them
form in their interior young or secondary cells. These
secondary cells originate in a germinal spot or nucleus, situated
about a third from the attached extremity of the cell. In
such of the spindle-shaped cells as are quite full of secondary
cells, this nucleus cannot be seen, so that it probably dis-
appears after the primary cells have become fully developed
that is, have become full of young. In such of these elongated
cells, again, as are not quite developed, with cavities not en-
tirely occupied by their progeny, the nucleus may be occasion-
ally seen in various stages of development, with a brood of
young cells surrounding it, and enclosed in a membrane carried
off by them from the nucleus (Pagurus).
These spindle-shaped primary cells of the lower part of
the seminal duct differ from the spherical primary cells of the
upper part of the same tube, principally in this, that whereas
the latter contain only a limited number of secondary cells,
formed probably by a single act of nuclear development, the
former are filled by successive broods from the nucleus.
In Hyas, when these spindle-shaped cells project from the
external surface of the seminal duct, instead of into its cavity,
the secondary cells pass off by a narrow valvular orifice in its
attached extremity, and are replaced by others from the
nucleus. The cell in this case has become a secreting follicle,
with an active germinal spot.
The passage downwards of the secondary cells, both of the
TESTIS IN DECAPODOUS CRUSTACEA. 433
superior spherical, and the lower spindle-shaped primary cells,
is retarded in the neighbourhood of the latter by long slips or
bands, which run up the cavity of the duct and terminate by
free edges ; the direction of these bands being opposed to the
flow of the seminal fluid downwards.
These peculiar spindle-shaped cells or acini, although
present in all the orders, are most apparent in the Anomoura
and cuirassed Macroura. In the Triangulares and succeeding
families of Brachyura, also in lower families of Macroura, from
the Cryptobranchiate genera and downwards, they are by no
means so elongated, resembling rather widened and contracted
portions of the seminal duct. The arrangement is similar in
the lower orders as in Stomapoda, Ampliipoda, and Isopoda
the Lcemodipoda being apparently exceptions to the rule.
Neither is this structure found in Branchiopoda, Entomostraca,
Siphonostoma, and Xipliosura, in which orders the structure
of the testis would require for elucidation a separate inquiry.
The secondary cells, as has already been stated, continue
to be developed in their progress along the seminal tube. At
the spot where they are retarded by the folds at the necks of
the spindle-shaped cells, they increase much in size, from the
increased number and size of their contained cells. After this
no great change takes place, with the exception of a thinning
of the walls. In this state they pass along the narrow part
of the duct, or vas deferens, and are thrown during coitus into
the spermatheca of the female, there to undergo the essential
change which is to fit them for fertilisation of the ova.
That this final change can only take place in the sperma-
theca of the female does not appear to be the case, for
precocious secondary cells may occasionally be found bursting
in the lower part of the seminal tube, and even as high up as
the spindle-shaped cells. The greater number, indeed, with a
few exceptions the whole of them, are introduced into the
female before bursting.
2 F
434 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
After lying in the spermatheca for some time, the wall of
the secondary cell becomes so thin that it bursts, and allows
the young cells to escape. These tertiary cells contain, and
are, the formative cells of the spermatozoa. In the higher
Crustacea, Brachyura, they each contain one or more sperma-
tozoa, in the Macroura one only. The spermatozoal cells are
nucleated when they first burst from the secondary cells, and
shortly the head of the spermatozoa is found to correspond to
the nucleus.
The seminal fluid in all the species of Macroura is very
peculiar, the tertiary cells being in all cases armed with three
long slender setae.* They are oblong, and dilated at the
armed extremity. They are developed singly within their
parent cells ; sometimes, however, two may be observed in
one cell. These parent or secondary cells are oblong, and
bulge slightly in the middle. After they have remained for
some time in the spindle-shaped caeca (Galathed), the three
setae of the tertiary cell expand, and the cells begin their
descent. In the progress downwards, the unarmed extremity
acquires a small nucleated spot, and in many instances small
spherical cells are thrown off from this, which are quaternary,
and probably spermatozoal cells. In the cuirassed and digging
Macroura these tertiary cells are all armed with three setae,
many times longer than the body of the cell. In the prawn
these setae are short and truncated.
Throughout the whole course of the lower part of the
seminal tube there may be observed during the active state
of the gland, and while the seminal cells are being produced,
a large quantity of albuminous matter in small irregular
masses floating among the cells in an aqueous fluid. I am
induced to believe that the cells derive their nourishment
from this matter.
In the upper part of the tube, where the cells are small
* Von Siebold in Miiller's Archiv, 1836.
TESTIS IN DECAPODOUS CRUSTACEA. 435
and comparatively few in number, this matter is in small
quantity ; but in the lower part of the tube, where the cells
are more numerous, more developed, and in a more active
condition, it exists in the greatest abundance. Still lower
down in the vas deferens, where the cells are in a state of
satiety, and are in fact absorbing principally their own external
wall, preparatory to bursting, it again diminishes in quantity,
and disappears.
This albuminous matter would appear to result from the
debris of dissolved cells. It is more abundant in the
Brachyura than in the other forms of Crustacea, in accordance
with the greater abundance of seminal cells.*
H. D. S. G.
* An abstract of more extended observations on the subject of this chapter
was published in the Ed. Phil. Journal, October 1843.
436 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
XXVIL THE STKUCTUKE OF THE SEROUS
MEMBRANES.
A PORTION of the human pleura or peritoneum will be found
to consist, from its free surface inwards, of a layer of nucleated
scales, of a germinal membrane,* and of the sub-serous
areolar texture intermixed with occasional elastic fibres.
The bloodvessels of the serous membrane ramify in the
areolar texture.
There is one stratum only of the nucleated scales in the
superficial layer of the serous membrane. This layer con-
ceals the germinal membrane, which can only be detected
after the removal of the scales.
The germinal membrane does not in general show the
lines of junction of its component flattened cells. These
appear to be elongated in the form of ribbons their nuclei,
or the germinal spots of the membrane, being elongated, ex-
panded at one extremity, pointed at the other, and somewhat
bent upon themselves. The direction of these flattened cells
and nuclei is the same in any one part of the membrane, this
direction being in general parallel to the subjacent blood-
vessels, in the neighbourhood of which they exist in greatest
numbers. The germinal spots are bright and crystalline, and
may, or may not, according to their condition, contain smaller
cells in their interior. They are not to be confounded with
* I stated this fact in my Paper on the Intestinal Villi, in the Ed. Phil.
Journal, July 1822. Dr. Todd and Mr. Bowman, in their Physiology of
Man, have described the same membrane in the serous texture.
STRUCTURE OF SEROUS MEMBRANES. 437
the fibres of the areolar texture, or with elastic filaments, or
with the nuclei of the capillary vessels of the subserous
texture, or with paler, ovoidal, somewhat indistinct cells,
scattered throughout that texture, and which appear to be
connected with the common areolar fibres.
These flattened ribbon-shaped scales, and bright crystalline
nuclei, which form the germinal or basement membrane of
the serous coat appear to be identical with the objects de-
scribed by Valentin,* Pappenheim,t and Henle,J and named
by the latter nucleated fibres.
In inflamed or aged serous membranes, I have found it
impossible to detect this membrane, or even the superimposed
scales. The germinal membrane in such instances appears to
break up into areolar texture, and to assimilate itself to the
bursae mucosse, or the ordinary enlarged areolae of the areolar
texture.
If these germinal centres be the sources of all the scales
of the superficial layer, each centre being the source of the
scales of its own compartment, then the matter necessary
for the formation of these during their development must
pass from the capillary vessels to each of the centres acted on
by forces whose centres of action are the germinal spots ;
each of the scales, after being detached from its parent centre,
deriving its nourishment by its own inherent powers.
I have been in the habit of considering the highly vascular
fringes and processes of the synovial membranes as more
active in the formation of epithelium, and therefore more
closely allied to the secreting organs, than other portions of
these membranes. If this be the case, Clopton Havers was
not mistaken in his ideas regarding the functions of these
* Valentin, Repertorium, 1838.
t Pappenheim, Zur Kentniss der Verdauung, 1839.
+ Henle, Anatomie Allgemeine.
Clopton Havers, Osteologia Nova, 1691.
438 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
vascular fringes. They are situated where they cannot inter-
fere with the motions of the joint. They hang into those
parts of the cavity best fitted for containing and acting as
reservoirs of svnovia; and their high vascularity, and the
pulpy nature of their serous covering, tend to strengthen this
opinion.
The phenomena attending inflammatory action of the
membranes are highly interesting. The capillaries are all on
one side of the membrane, and yet the serum and lymph are
on the other. The capillary vessels in healthy action have
no power in themselves of throwing out any of their contents.
They do not secrete in virtue of any power inherent in them-
selves. Do they acquire this power during inflammation?
Or will any of the hypotheses of effusion account for the
lymph and serum being on the free surface of the serous
membranes, and so little, if any, in the subserous textures ?
I do not see how we can, in the present state of the
science, account for phenomena of this kind by referring
them to actions of the extreme vessels. We must look for
an explanation, I am inclined to believe, in a disturbance of
the forces which naturally exist in the extravascular portions
of the inflamed part. *
* "The primary change," in inflammation, "is in the vital affinities,
common to the solids and fluids, and acting chiefly in that part of the system
where the solids and fluids are most intimately mixed, and are continually
interchanging particles." Alison's Outlines of Physiology and Pathology, page
437.
STRUCTURE OF LYMPHATIC GLANDS. 439
XXVIIL STRUCTURE OF THE LYMPHATIC
GLANDS. (PLATE V.)
IT is now generally admitted, that the afferent communicate
in the interior of the lymphatic glands with the efferent
vessels. These glands, indeed, consist of a dense network of
lymphatics, in the meshes of which the arteries, veins, and
nerves ramify. Much difference of opinion still exists, how-
ever, as to the nature of the communication between the
afferent and efferent vessels, and no definite idea is enter-
tained regarding the parenchyma of these organs.
We know that an efferent lymphatic, before it enters a
gland, consists of an external tunic of filamentous texture, a
middle tunic of fibrous texture, and an internal layer of epi-
thelium.
Immediately after the branches, into which the afferent
vessel divides, have penetrated the capsule of the gland, they
lose their external tunic. For a short distance, indeed, until
they have begun to anastomose with one another, a very thin
external tunic, accompanied by a little fat, is still observable.
This fat is continuous with the layer of adipose texture which
generally exists immediately under the capsule of the gland,
and through which the lymphatics must pass to and from the
organ.
The branches of the extra-glandular lymphatics, then,
which pass to and from the glands, possess a very thin inter-
nal tunic ; but the network of intra-glandular lymphatics
which enter into the structure of the gland itself, presents no
440 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
external coat. The external tunic of the extra-glandulai
lymphatics the afferent and efferent vessels appears to
leave them almost entirely at their entrance and exit from
the organ, and by passing on to the surface of the gland forms
its capsule.
This capsule is moderately strong, somewhat smooth on
its free, more filamentous on its attached surface, sending in-
wards from the latter the processes already described, which
not only support the larger branches of the vessels before
they anastomose, but also bind together and strengthen the
substance of the organ. The larger trunks of the arteries and
veins, as they pass through the capsule, and plunge into the
substance of the gland, carry along with them also a certain
quantity of filamentous texture, which is derived from the
internal surface of the capsule, and is continuous with the
processes which surround the larger lymphatic branches.
The middle or fibrous tunic of the extra-glandular lymph-
atics, also begins to disappear after these vessels have pene-
trated the capsule of the gland. It is still sufficiently ap-
parent on the lymphatics near the surface of the organ, but
is met with sparingly towards the centre. Different glands,
however, differ in this respect ; the human intra-glandular
lymphatics appearing to me to retain more of their fibrous
tunic than those in the more granular and developed mesen-
teric glands of the dog and seal.
It is, however, to the changes which the internal tunic of
the intra-glandular lymphatics undergoes, that I shall now
more particularly direct attention, as these have hitherto
escaped observation, and as upon them depend those appear-
ances and peculiarities which are yet unexplained.
I shall first describe the internal tunic, and afterwards its
arrangement.
If this tunic be traced from the afferent lymphatics, in
which it presents the usual structure, into the branches im-
STRUCTURE OF LYMPHATIC GLANDS. 441
mediately after they have penetrated the capsule of the gland,
it is found to become thicker and more opaque. In the short
dilated anastomosing branches which form the intra-glandular
network this tunic has become so thick and opaque, that the
vessels will no longer transmit the light, and appear as if they
were stuffed full of a granular matter. When these thickened
and dilated vessels are cut, torn, or broken, so as to display
their structure, it may be observed that two parts enter into
their composition an extremely fine external membrane, and
a thick granular substance, which lines the membrane.
The external membrane is extremely thin and transparent.
In its substance there are arranged, at regular distances,
ovoidal bodies, so placed that their long diameters are all in
the same direction. The distance of these bodies from one
another is somewhat greater than their long diameters. They
are imbedded in the substance, and form a part of the mem-
brane. They are hollow, and contain one or more rounded
vesicles grouped together in their interior. I have seen
portions of this membrane, after it has been acted upon by
acetic acid, present an appearance of being broken up into
flat semi-transparent scales, united by their edges each scale
consisting of one of the nucleated ovoidal bodies, and a
portion of the surrounding membrane.
The thick granular substance which is attached to the
internal surface of the membrane just described, is composed
entirely of nucleated particles, closely packed together, and
cohering to one another. The thickness of this layer of
granular substance is so considerable as to render the vessel,
of which it is a part, almost opaque, encroaching on its cavity,
and leaving a comparatively narrow canal for the passage of
the lymph and chyle. This canal appears to be somewhat
irregular, in consequence of the greater exuberance of the
granular substance in some spots, and its deficiency in others.
This circumstance also accounts for the greater transparency
442 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
of the vessels at certain parts of their extent. The canal is
not lined by a membrane, but appears to me to be irregularly
pierced through the granular substance, the projections and
hollows of which, as well as the superficial layer of its nucle-
ated particles, being freely bathed by the lymph and chyle.
The nucleated particles are on an average about the 5000th
of an inch in diameter. They are spherical, and contain a
nucleus, which consists of one or more particles. Their walls
are very distinct, especially after being treated with acetic acid,
which reduces their size somewhat, without dissolving or
breaking them up.
The layer of particles which has now been described is
thickest in the lymphatics towards the centre of the gland.
If it be examined in either direction towards the afferent or
efferent branches, it will be found to become thinner, and, at
last, to be continuous with the layer of flat epithelium-scales
of the extra-glandular lymphatics.
The anatomical relations of the membrane, and its layer
of nucleated particles, are identical with those which charac-
terise the primary cells or membrane, and the secondary or
secreting cells of certain glands. The oval vesicles in the
substance of the membrane are germinal spots or centres of
nutrition, and the membrane is a germinal membrane. I am
inclined to believe the spots on the membrane to be the
sources from which the germs of the nucleated particles of
the thick layer are derived. These spots are doubtless in a
state of constant activity in all lymphatic glands, but must
be called into much more vigorous action periodically in the
mesenteric glands, during the passage of the chyle. If this
be the case, these spots must exert a force by which matter
is abstracted from the blood which circulates in the neighbour-
ing capillaries, for the purpose of developing a steady succes-
sion of nucleated particles.
The arrangement in the substance of the lymphatic glands
STRUCTURE OF LYMPHATIC GLANDS. 443
of this highly-developed portion of the lymphatic system of
vessels, or, in other words, the mode in which the afferent
communicate with the efferent lymphatics, I have found to
coincide with the account usually given of it. The terminal
branches of the afferent form a more or less dense network
with the radicals of the efferent lymphatics. The question
which has been so often agitated, as to whether cavities exist,
intermediate between the two sets of lymphatics, is not one
of much importance. Some lymphatic glands, as has fre-
quently been stated, exhibit, after injection with mercury,
nothing but a mass of lymphatic vessels ; others, again, a
mass of apparently intermediate cells ; and Cruikshank cor-
rectly remarks, that occasionally, when the mercury first
passes through a gland, cells only may appear, but after the
injection has been pushed a little further, vessels full of mer-
cury may suddenly present themselves.*
These various appearances may be explained by the
following facts : In some lymphatic glands the meshes are
elongated, in which case no force short of what is sufficient
to burst the vessels can obliterate the vascular appearance.
The intra-glandular lymphatics, like those in other parts, are
liable to be over-distended with injections, or by their own
contents, so that short vessels or rounded meshes, more
especially after great distension, assume the appearance of
globular cavities.
There is another apparently cellular appearance, which is
not met with in the human lymphatic glands, but in some of
the lower mammals, which is produced by another cause the
partial or entire obliteration of some of the meshes, so as to
produce cavities more or less extended, with bars or threads
passing from wall to wall, the lymphatics opening into them.
This is the conversion of a network of lymphatics into cavities
* Cruikshank, The Anatomy of the Absorbing Vessels of the Human Body,
page 82.
444 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
and connecting threads, by a process of absorption similar to
that which I have to describe as occurring in the placental
decidua.*
The external surfaces of the intra-glandular lymphatics
are closely applied to one another. They are strengthened
here and there by fibrous bundles, the remains of the middle
tunic. These fibres are most distinct towards the surface of
the glands, and at the angles formed by the junction of one
lymphatic with another ; and when viewed in thin sections
seem to form arches inclosing circular or oval spaces, like the
fibrous matrix of the human kidney.
The description usually given of the arrangement of the
bloodvessels in the lymphatic glands is sufficiently correct.
The ultimate capillaries, as I have observed, do not ramify in
the substance of the germinal membrane of the intra-glandular
lymphatics, but are merely in contact with its external surface.
In this respect they resemble the ultimate ducts of the true
secreting glands.
The capillary network which surrounds the intra-glandular
lymphatics is as fine as that which supplies the ultimate
secreting ducts, and for the same purpose in both, to afford
matter for the continued formation of secreting epithelium on
the internal surface of the germinal membrane.
The structure I have described affords, in my opinion,
satisfactory evidence
1. That the lymphatic glands are merely networks of
lymphatic vessels, deprived of all their tunics but the internal,
the epithelium of which is highly developed for the per-
formance of particular functions.
2. That these peculiar lymphatics are supplied with a fine
capillary network, to supply matter for the continual renovation
of the epithelium.
* See page 457.
Plate VI
"?3K
-\ ""N^ 2
( , .\ <} N
- J c
o^
00
flOO
I I
O
=ssr^lfeo
STKUCTTJRE OF HUMAN PLACENTA. 445
XXIX. THE STKUCTUEE OF THE HUMAN
PLACENTA. (PLATES V. VI.)
I. OF THE STRUCTURE OF THE TUFTS AND VILLI OF THE
PLACENTA.
1. Of the Configuration of the Tufts.
A PLACENTAL tuft resembles a tree. It consists of a trunk,
of primary branches, and of secondary branches or terminal
villi, which are attached as solitary villi to the sides of the
primary branches, and to the extremities of the latter, in which
case they generally present a digitated arrangement. The
villus, when solitary, is cylindrical, .or slightly flattened, or
somewhat club-shaped ; when digitated, each division may be
much flattened, or is then generally heart-shaped. The
digitated villi are only solitary villi grouped together at the
extremity of a primary branch.
2. Of the External Membrane of the Tufts.
The trunk, the primary branches, and the terminal villi of
the tuft are covered by a very fine transparent membrane,
apparently devoid of any structure. This membrane may be
described as bounding the whole tuft, passing from the trunk
to the branches, and from these to the villi, the free extremities
of which it closely covers. Its free surface is smooth and
glistening its attached surface is somewhat rough.*
* Professor Reid, " On the Anatomical Relations of the Bloodvessels of the
Mother to those of the Fostus in the Human Species." Ed. Med. Surg. Journal,
1841, page 7.
446 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
3. Of the External Cells of the Villi.
Immediately under the membrane just described is a layer
of cells.* They are flattened spheroids, slightly quadrilateral
in outline, from the manner in which they are packed together.
When a tuft is viewed in profile, under compression, its edges
exhibit the appearance of a double line, which leads the
observer to suppose that its bounding membrane is double,
with the cells just described situated between the two laminae.
In the space between the two lines, the nuclei of the cells may
be seen in the form of dark oval spots, and the septa formed
by the walls of contiguous cells are also visible.
At variable distances the space between the two lines
widens out into a triangular form, the base towards the external
membrane, the apex towards the centre of the villus. This
wider space is produced by a larger group of cells, which ap-
pear to be passing off from a spot in the centre of the mass.
The groups of cells I am now describing are germinal spots.
They are the centres from which new cells are constantly
passing off, to supply the loss of those which have disappeared
in the performance of their important function.
As in the case of the intestinal epithelium, I am inclined
to believe that a fine membrane lines the internal aspect of the
layer of cells. I have not been able to isolate it ; but the very-
sharp outline in a profile view of a villus confirms me in my
belief of the existence of such a membrane.
4. Of the Internal Membrane of the Villus.
When a villus, under gentle compression, is viewed by
transmitted light, there is perceived under the structures
already described, and immediately bounding the blood-
* Mr. Dalrymple, "On the Structure of the Placenta." Med. Chir. Trans.
London, vol. xxv. pages 23, 24.
STRUCTURE OF HUMAN PLACENTA. 44*7
vessels, and other parts to be afterwards examined, a
membrane finer and more transparent than the external
membrane, but strong and firm in its texture. This membrane
is most distinctly s.een when it passes from one loop or coil
of the bloodvessel of the villus on to another. It separates
very easily from the internal surface of the layer of external
cells. I am not disposed to believe that it is attached to this
layer, but am of opinion that the spaces which frequently
exist between them, even in villi which have undergone no
violence, are due to the presence of a fluid matter, the nature
of which will be afterwards considered. Be this as it may,
pressure very easily separates this membrane from the external
cells the latter invariably remaining attached to the external
membrane, the former continuing in every instance closely
rolled round the internal structures of the villus, and following
them in all their changes of position.
5. O/ the Bloodvessels of the Tufts.
Within the internal membrane, and imbedded in structures
to be afterwards described, are situated the bloodvessels of
the tuft. These vessels are branches of the umbilical arteries
and veins.
In the trunk of the tuft, the artery gradually diminishes
and the vein increases in size. In some of the primary
branches the same relation holds. In others of the primary-
branches, and in all the villi, the vessel retains the same mean
diameter throughout. This species of bloodvessel, although
it cannot be considered as either artery or vein, cannot never-
theless be denominated, in precise anatomical language, a
capillary. It differs from artery and vein in retaining
throughout the same mean diameter ; and from the capillary,
properly so called, in its greater calibre, containing four or six
blood-discs abreast. It is also peculiar in exhibiting sudden
constrictions and dilatations, like an intestine.
448 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
These changes in form are most remarkable at the spots
where the vessel makes sudden turns, coils, or convolutions.
Like a capillary, however, this vessel may divide and again
become single, and may send off a division to a vessel of the
same kind. All such divisions and anastomosing vessels,
however, preserve the same mean diameter, and are in this
respect distinguishable from arterial and venous branches.
As regards the general arrangement of the vessels, it may
be observed that
1. One vessel may enter a villus, and, returning on itself,
leave it again.
2. Two vessels may enter a villus, may anastomose, and
leave it in one or two divisions.
3. One or more may enter, may each separate into two
or more divisions, which may reunite and leave the villus as
they entered.
Many other modifications occur, but the general rule is,
that one vessel enters and leaves the villus without dividing.
As regards the particular arrangements of the vessels
within the villus, we recognise those leading varieties :
1. The simple loop, a vessel turning closely on itself.
2. The open loop, a vessel turning on itself, but leaving a
space within the loop.
3. The wavy loop, resembling the first, except that the
vessel is wavy instead of being direct.
4. The wavy open loops.
5. The contorted loop, the contortion being generally at
the extremity or sling of the loop ; the limbs of the loop
being straight or wavy as the case may be.
6. The various modifications which arise from combina-
tions of the five foregoing forms, in single, double, triple, or
quadruple or anastomosing loops. The most common forms
are the simple and contorted loop. The simple loop and the
wavy loop are found in cylindrical villi. The open loop and
STRUCTUKE OF HUMAN PLACENTA. 449
the wavy open loop, occur in the flattened and heart-shaped
villi. The contorted and other varieties of loops exist in the
club-shaped and tuberose villi.*
Lastly, It must be stated as a fact first recorded and
represented by Professor Weber, confirmed by the observations
of Mr. John Dalrymple, and to the accuracy of which I can
testify, that the same peculiar vessel, or umbilical capillary,
may enter and retire from two or more villi before it becomes
continuous with a vein.
6. Of the internal Cells of the Villus.
Within the internal membrane, and on the external
surface of the umbilical capillaries, are cells which I have
named the internal cells of the tuft. When the vessels are
engorged, these cells are seen with difficulty. When the
vessels are moderately distended, and the internal membrane
separated from the external cells by moderate pressure, the
cells now under consideration come into view. They are best
seen in the spaces left between the internal membrane and the
retiring angles formed by the coils and loops of the vessels,
and in the vacant spaces formed by these loops. These cells are
egg-shaped, highly transparent, and are defined by the instru-
ment with difficulty ; but their nuclei are easily perceived.
They appear to be filled with a transparent highly refractive
matter. This system of cells fills the whole space which
* Mr. Dalrymple, in his paper on the Placenta, in the Med. Chir. Trails.,
has described with great accuracy the manner in which the foetal vessels ramify
and coil in the tufts of the placenta. I am indebted to Mr. Dalrymple for
specimens of his injections of the placenta ; and to Dr. John Eeid, for a portion
of a placenta injected by Professor "Weber of Leipsic, and have satisfied myself
of the accuracy of the descriptions given by these anatomists. My own obser-
vations have been made on the unprepared placenta. The drawings of the
foetal vessels in Dr. Reid's paper are plans, as the only point he was anxious
to establish was, that the villi terminated in blunt extremities unconnected by
cellular or other textures, the foetal vessels returning upon themselves. REID,
in Edinburgh Medical and Surgical Journal.
2 G
450 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
intervenes between the internal membrane of the villus and
the vessels, and gives to this part of the organ a mottled
appearance.
II. OF THE VILLI OF THE CHORION.
Without entering at present into the question as to the
manner in which the villi of the chorion take their origin, 1
may state, that as soon as they are distinctly formed, they
present a structure which has to a certain extent been repre-
sented and described by Easpail,* Seiler,t and others.
The substance of the tufts consists of nucleated cells.
These cells are of different sizes. The smaller are situated,
some in the interior, others in the spaces between the latter.
The cavities of the larger cells are full of a granular fluid.
The surface of the tufts is bounded by a fine but very distinct
membrane, which, when minutely examined, is seen to consist
of flattened cells united by their edges.
The free extremity of each villus of the tuft is bulbous.
The cells which constitute this swelling are arranged round a
central spot. They are transparent and refractive, apparently
from not containing the same granular matter as the cells of
the rest of the villus and tuft. However short a villus may
be, it invariably presents a bulbous extremity, with the
peculiar cellular arrangement already described. Here and
there, on the sides of the stems of the tufts, swellings of a
similar structure may be seen. Each of these swellings is
the commencement of a new villus or stem, which, as it
elongates, carries forward on its extremity the swelling from
which it arose.
These groups of cells in the bulbous extremities of the
villi of the chorion, and in the swellings on the sides of their
* Raspail. Chemie Organiqm.
t Seller. Gebarmuiter und das Ei des Menschen in den ersten Schivanger-
schaftsmonaten.
STRUCTURE OF HUMAN PLACENTA. 451
stems, are the germinal spots of the villi. They are the active
agents in the formation of these parts. The villus elongates
by the addition of cells to its extremity, the cells passing off
from the germinal spot, and the spot receding on the extremity
of the villus, as the latter elongates by the additions which
it receives from it.
The bulbous extremities of the villi of the chorion, are not
only the formative agents of these parts, but are also all along,
but principally after the villi have become well developed,
their functional agents also. They are to the ovum what the
spongioles are to the plant they supply it with nourishment
from the soil in which it is planted.
Up to a certain period of gestation, the chorion and its villi
contain no bloodvessels. Bloodvessels first appear in these
parts when the allantois reaches and applies itself to a certain
portion of the internal surface of the chorion. The umbilical
vessels then communicate with the substance of the villi, and
become continuous with loops in their interior. Those villi in
which the bloodvessels do not undergo any further develop-
ment, as the ovum increases in size, become more widely
separated, and lose their importance in the economy. The
villi, again, in which vessels form, in connection with the
umbilical vessels, increase in number, and undergo certain
changes in the arrangement of their constituent elements, so
as to become the internal structures of the tufts of the
placenta, as described in the first part of this Memoir. The
villi of the chorion always retain their cellular structure. As
the bloodvessels increase in size the cells diminish in number ;
but are always found surrounding the terminal loop of vessels
in the situation of the germinal spot. The fine membrane,
which was formerly described as bounding the villus of the
chorion, always remains at the free extremities of the villi of
the placenta ; but on the stems and branches of the latter it
coalesces with the contained cells.
452 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
The conversion into fibrous texture of the membrane and
cells of the stems and branches of the tuft of the chorion,
forms the tough white fibrous trunk and branches of the tufts
of the foetal portion of the placenta ; in each of which runs a
branch of the umbilical arteries and vein ; and the fine mem-
brane of the villi of the chorion, with its contained cells and
terminal bloodloops, still persistent at the extremities of the
villi, are the internal membrane, the internal cells, and the
bloodloops described in the first part of this Memoir.
III. OF THE MATERNAL PORTION OF THE PLACENTA.
The mucous membrane of the uterus presents on its free
surface the orifices of numerous cylindrical follicles arranged
parallel to one another, and at right angles to the surface. In
the spaces between these follicles the bloodvessels form a
dense capillary net-work.
From the observations of Professors Weber and Sharpey,*
it has now been ascertained, that when impregnation has
taken place, the mucous membrane of the uterus swells, and
becomes lax, that its follicles increase in size, and secrete a
granular matter, and that the capillaries increase in a propor-
tional degree. " In a uterus," says Dr. Sharpey, " supposed
to have been recently impregnated, and in which the vessels
had been minutely injected with vermilion, the lining mem-
brane, or commencing decidua, appeared everywhere pervaded
by a net-work of bloodvessels, in the midst of which the
tubular glands were seen, their white epithelium strongly con-
trasting with the surrounding redness." It must have been
from a uterus in this condition that Von Baer took the sketch
of the structure of the commencing decidua, which has been
copied by Wagner in his Icones Physiologicce. Von Baer and
Wagner, however, have mistaken the enlarged follicles for
* Miiller's Physiology, page 1574.
STRUCTURE OF HUMAN PLACENTA. 453
papillae, and have represented the capillary loops in a manner
much too formal. I have examined a uterus which was in a
state described by Dr. Sharpey. There was a well-formed
corpus luteum in one of the ovaries ; the decidua had appeared
on its internal surface, and presented in the most distinct and
beautiful manner the orifices of the follicles, and the vascu-
larity of the interfollicular spaces. The follicles, bounded by
their germinal membrane, were turgid with their epithelial
contents. The interfollicular spaces in which the capillaries
formed a net-work with polygonal or rounded meshes, was
occupied by a texture which consisted entirely of nucleated
particles. This is the tissue represented by Von Baer and
Wagner, described by them as surrounding what they supposed
to be uterine papillae, and considered by them as decidua. The
free surface of the uterine mucous membrane was covered by
a membrane which appeared to me to be continuous with the
germinal membrane of the follicles.
Dr. Sharpey has not described this interfollicular sub-
s.tance, as his attention appears to have been chiefly directed
to the follicles. As, however, it is to this interfollicular sub-
stance, as much as to the enlargement of the follicles them-
selves, that the mucous membrane owes its increased thickness,
it appears to me worthy of being recorded.
A uterus in the condition which has just been described,
is said to be lined with the decidua, consisting, as has been
stated, of an interfollicular cellular substance, and of an ex-
tended net-work of capillary bloodvessels.
About the time at which the ovum reaches the uterus, the
developed mucous membrane or decidua begins to secrete,
the os uteri becomes plugged up by this secretion, where it
assumes the form of elongated epithelial cells ; the cavity of
the uterus becomes filled with a fluid secretion, the " hydro-
perione " of Breschet, and in the immediate neighbourhood of
the ovum, the secretion consists of cells of a spherical form.
454 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
The cells which are separated in the neighbourhood of the
ovum I consider as a secretion of the third order. They have
passed off from the uterine glands entire, and possess a power
peculiar to the third order of secretions, the power of under-
going further development after being detached from the ger-
minal spots or membrane of the secreting organ.
Prom what has now been stated, it appears that the
decidua consists of two distinct elements ; the mucous mem-
brane of the uterus thickened by a peculiar development, and
of a non-vascular cellular substance, the product of the uterine
follicles. The former constitutes at a later period the greater
part of the decidua vera, the latter, the decidua reflexa. This
view of the constitution of the decidua, clears up the doubts
which were entertained regarding the arrangement of these
membranes at the os uteri, and entrances of the Fallopian
tubes. It is evident that these orifices will be open or closed,
just as the cellular secretion is more or less plentiful, or in a
state of more or less vigorous development. It also removes
the difficulty of explaining how the decidua covers the ovum,
a difficulty which cannot be reconciled with the views of Dr.
Sharpey, who is obliged to suppose the deposition of lymph,
which is only the old view of the constitution of the decidua.
When the ovum enters the cavity of the uterus, the cellu-
lar decidua surrounds it, and becomes what has been named
the decidua reflexa, by a continuation of the same action by
which it had been increasing in quantity before the arrival of
the ovum. The cellular decidua grows around the ovum by
the formation of new cells, the product of those in whose
vicinity the ovum happens to be situated.
At this stage of its growth, the ovum with its external
membrane, the chorion, covered by tufts, the structure and
functions of which have been described in the second part of
this Memoir, is imbedded in a substance which consists
entirely of active nucleated cells. The absorbing cells of the
STRUCTURE OF HUMAN PLACENTA. 455
tufts are constantly taking up either the matter resulting from
the solution of the cells of the cellular decidua, or the fluid
contained in these cells. The ovum is now deriving its
nourishment, not from the supply which it took along with it
when it left the ovary, but from a matter supplied by the
uterus. I am, therefore, inclined to look upon the cellular
decidua as representing, in the gestation of the mammal, the
albumen of the egg of the oviparous animal. They are both
supplied by a certain portion of the oviduct, and they are
both brought into play after the nourishment supplied by the
ovary is exhausted, or in the course of being exhausted. The
difference between them consists in this, that in the mammal
the albumen is applied to use as quickly as it is absorbed ;
whereas, in the oviparous animal, after being absorbed, it is
kept in reserve within the chorion till required. I have also
been in the habit of considering the uterine cotyledons of the
ruminant and other mammalia as a permanent decidua vera,
and the milky secretion interposed between them and the
foetal cotyledons as decidua reflexa in its primitive and
simplest form.
I have been thus particular in the explanation of what I
believe to be the nutritive function performed respectively by
the chorion and decidua, as upon it I shall have to found my
views regarding the actions of nutrition in the fully developed
placenta.
When the ovum has arrived at a certain stage of its growth,
the absorption and circulation of nutritive matter by the
agency of cells alone is no longer sufficient. At this period,
the ovum has approached the thickened mucous membrane,
or that portion usually described as decidua serotina. About
the same time, the allantois bearing the umbilical vessels
applies itself to the internal surface of that portion of the
chorion opposed to the decidua serotina, and the villi of that
portion become vascular, as formerly described. The vessels
456 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
of the decidua enlarge, and assume the appearance of sinuses
encroaching on the space formerly occupied by the cellular
decidua, in the midst of which the villi of the chorion are
imbedded. This increase in the calibre of the decidual capil-
laries goes on to such an extent, that finally the villi are
completely bound up or covered by the membrane which
constitutes the walls of the vessels, this membrane following
the contour of all the villi, and even passing to a certain
extent over the branches and stems of the tufts. Between
this membrane, or wall of the enlarged decidual vessels, and
the internal membrane of the villi, there still remains a layer
of the cells of the decidua.
From this period, up to the full time, all that portion of
decidua in connection with the group of enlarged capillaries
and vascular tufts of the chorion, and which may now be
called a placenta, is divided into two portions. The first
portion of the decidua, in connection with the placenta, or
forming a part of it, is situated between that organ and the
wall of the uterus. This is the only portion of the placental
decidua with which anatomists have been hitherto acquainted,
and I shall name it the parietal portion. It has a gelatinous
appearance, and consists of rounded or oval cells. Two sets of
vessels pass into it from the uterus. The first set includes
vessels of large size which pass through it for the purpose of
supplying the placenta with maternal blood for the use of the
foetus. These may be named the maternal functional vessels
of the placenta. The second set are capillary vessels, and
pass into this portion of the decidua for the purpose of
nourishing it. These are the nutritive vessels of the placenta.
The account given by Mr. Hunter of the manner in which
the functional vessels of the placenta pass through this
portion of the placental decidua is still doubted by many,
notwithstanding the more recent of Mr. Owen's* dissections,
* Owen. Palmer s Edition of John Hunter's Works, vol. iv.
STRUCTURE OF HUMAN PLACENTA. 457
and the observations of Dr. Keid.* I have dissected the
vessels of an unopened uterus at the full time in the manner
adopted by Mr. Owen, by opening one of the large veins over
the spot to which the placenta was attached. Introducing a
probe as a guide, I slit open the vein with a pair of scissors,
and repeated the same process with the probe and scissors
whenever a branch entered the vein already opened. I gra-
dually passed through the wall of the uterus. In my progress,
I occasionally found that when the probe was pushed along
an unopened vein, its point appeared at another opening ; and
as I approached the internal surface of the wall of the uterus,
these anastomoses of the veins became more numerous, the
spaces which they inclosed presenting the appearance of
narrow flat bands. At last, in introducing the probe under
the falciform edges of the venous orifices, it was found to
have arrived at the placental tufts, which could be seen by
raising the edges of the falciform edges. Having passed over
the falciform edges, the venous membrane suddenly passed
to each side to line the great cavity of the placenta. The flat
bands which I have just described as the spaces inclosed by
anastomosing venous sinuses, became smaller, and, on enter-
ing the cavity itself, the bands were seen to have assumed
the appearance of threads, which passed in great numbers
from the vascular edges of the venous openings, and from the
walls of the cavity of the placenta on to the extremities and
sides of the villi and tufts of the placenta. The whole mass
of spongy substance, that is the whole mass of tufts, was in
this manner perceived to be attached by innumerable threads
of venous membrane to that surface of the parietal decidua
of the placenta which was covered by the venous membrane.
On proceeding deeper into the substance of the placenta, I
perceived that, throughout its whole extent, villus was con-
nected to villus, and tuft to tuft, by similar threads of
* Reid. Edinburgh Medical and Surgical Journal, loc. cit.
458 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
venous membrane. Sometimes the apex of one villus was
connected to the apex of another. In other instances the
threads connected the sides of the villi. On minute examina-
tion these threads were found to be tubular, and the mem-
brane of which they were formed was seen to be continuous
in one direction with the lining membrane of the vascular
system of the mother, and in the other with the external
membrane of the tufts of the placenta, and passing from one
tuft, or set of tufts, on to another, so as to form the central
containing membrane of the bag of the placenta. These
threads, as well as their cavities, are somewhat funnel-shaped
at each extremity. The funnel-shaped portions of the cavities
of threads, and, in some instances, the whole length of the
tube, were found to be full of cells, which were continuous in
the one direction with the parietal decidua of the placenta,
and in the other with the external cells of the placental villi.*
This observation led me at once to perceive the real signi-
fication of the external cells of the placental tufts. I saw
that this great system of cells was a portion of the decidua,
all but cut off from the principal mass by the enormous
development of the decidual vascular network, but still con-
nected with it by the minute files of cells which fill the
cavities of the placental threads.
This system of cells, the external cells of the villus, with
the external membrane, are portions of the decidua, and, un-
like the other elements of the placental tufts, belong to the
organism of the mother. These cells, with their membrane, I
name the central division of the placental decidua, to dis-
tinguish it from the other portion formerly described, and
which I have already called the parietal division of the
placental decidua.
1. My observations have confirmed the statements of
* These are the reflections of 'the venous membrane of the mother, de-
scribed bv Dr. Reid.
STRUCTURE OF HUMAN PLACENTA. 459
Professors Weber and Sharpey as to the mode of formation of
the decidua vera ; but have led me to attach more importance
to the interfollicular substance, and to the secreted or non-
vascular portion of the decidua.
2. The placenta, as has long been admitted, consists of a
festal and of a maternal portion intermixed. But the mater-
nal portion, instead of consisting of a part of the vascular
system of the mother only, includes the whole of the external
cells of the villi.
3. The external membrane of the placental villi is a por-
tion of the wall of the vascular system of the mother, continu-
ous with the rest of that wall, through the medium of the
placental threads and lining membrane of the placental
cavity.
4. The system of the external cells of the placental villi
belongs to the decidua, and is continuous with the parietal
division through the medium of the cavities of the placental
threads. This portion of decidua has been named the central
division of the placental decidua, and the threads decidual
bars.
5. The function of the external cells of the placental villi
is to separate from the blood of the mother the matter
destined for the blood of the foetus. They are, therefore,
secreting cells, and are the remains of the secreting mucous
membrane of the uterus.
6. Immediately within the external cells of the placental
villi there is a membrane which I have named the internal
membrane of the villi. This membrane belongs to the system
of the foetus, and is the external or bounding membrane of
the villi of the chorion.
7. Inclosed within the internal membrane of the placental
villi is a system of cells, which belong to the system of the
foetus, and are the cells of the villi of the chorion. These are
the internal cells of the placental villus.
460 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
8. The function of the internal cells of the placental villi
is to absorb, through the internal membrane, the matter secreted
by the agency of the external cells of the villi.
9. The external cells of the placental villi perform, during
intra-uterine existence, a function for which is substituted in
extra-uterine life the digestive action of the gastro-intestinal
mucous membrane.
10. The internal cells of the placental villi perform, during
intra-uterine existence, a function for which is substituted in
extra-uterine life the action of the absorbing chyle-cells of
the intestinal villi.
11. The placenta, therefore, not only performs, as has
been always admitted, the function of a lung, but also the
function of an intestinal tube.
STRUCTURE OF BONE. 461
XXX. THE STRUCTURE AND ECONOMY OF
BONE.
A TEXTURE may be considered either by itself, or in con-
nection with the parts which usually accompany it. These
subsidiary parts may be entirely removed without interfering
with the anatomical constitution of the texture. It is essenti-
ally non-vascular, neither vessels nor nerves entering into its
intimate structure. It possesses in itself those powers by
which it is nourished, produces its kind, and performs the
actions for which it is destined, the subsidiary or superadded
parts supplying it with materials which it appropriates by its
own inherent powers, or connecting it in sympathetic and
harmonious action with other parts of the organism to which
it belongs.
In none of the textures are these characters more
distinctly seen than in the osseous. A well-macerated bone
is one of the most easily made, and, at the same time, one of
the most curious anatomical preparations. It is a perfect
example of a texture completely isolated, the vessels, nerves,
membranes, and fat, are all separated, and nothing is left but
the non-vascular osseous substance.
The osseous texture of a fresh bone, considered in this
way, consists of two parts, a hard and a soft. The hard part,
composed of earthy salts, deposited in a cartilaginous matrix,
has already been carefully examined by anatomists. The
soft has not yet attracted attention, in consequence of the
manner in which it is isolated, divided into small portions,
and concealed in the cavities of the osseous corpuscles.
4C2 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
The hard part of the osseous texture, considered in a long-
bone, presents four surfaces, all communicating with one an-
other, a periosteal or external, a medullary or internal, a
Haversian or intermediary, and a corpuscular or canalicular.
The periosteal surface communicates with the Haversian in
three ways : by those Haversian canals which open in it ; by
the canal for the medullary artery gradually subdividing and
diminishing till it breaks up into arterial Haversian canals ;
and by the more numerous canals for the veins, principally
met with at the extremities of the bone. The medullary
surface is to be considered as a portion of the Haversian,
having been formed by the enlargement, and subsequent
blending of neighbouring Haversian canals into medullary
cavities and cancelli. The canalicular or corpuscular surface
forms the walls of the innumerable corpuscles and canaliculi,
and communicates by the latter with the Haversian, medullary,
and less freely with the periosteal surface.
The compact osseous substance, in which the corpuscles
and their canaliculi are situated, is not homogeneous in
texture. It consists of cells filled with bony substance,
ossified or calcified primordial cells.
The soft part of the true osseous texture is not con-
tinuous like the hard, but is divided, as has been stated, into
as many portions as there are corpuscles in the bone. Each of
these portions consists of a little mass of nucleated cells of
great transparency. They do not appear to extend along the
canaliculi, but to be confined to the cavity of the corpuscle.
These two parts, the hard and the soft combined, con-
stitute the true osseous texture. They differ from one an-
other only in this, that the cells of the one are ossified, those
of the other retain their original delicacy and softness. The
masses of soft cells in the corpuscles, I am inclined to
consider as the nutritive centres, germinal centres, or germinal
spots of the texture. These centres are the source of all the
STRUCTURE OF BONE. 463
hardened cells, each of them being the centre of all those
comprehended within the range of its own canaliculi. Each
of these soft germinal masses is the centre of attraction for
the proper nutriment of bone, and is the active agent in with-
drawing this from the vessels, and appropriating it, partly for
the nourishment of the hard cells, each of which has a centre
of attraction within itself, but more probably for the formation
of new calcigerous cells, as the old cells dissolve and their
debris falls back into the returning circulation. The canali-
culi are undoubtedly the principal channels for the passage
of nutriment from the capillaries to the calcigerous cells and
germinal centres. They are necessary in a hard texture, and
like similar canals and fissures in certain hard cells in vege-
tables, only appear at a late stage in the development of
bone. Each osseous corpuscle has its own system of canali-
culi, these extending, for the purpose of communicating with
others, to the confines of its own territory ; that is, to the
boundaries of the space which was at one time contained
within the sphere of the primary cell of which it was the
nucleus.
The accessory parts of the osseous texture are the vessels,
nerves, membranes, and oil. For my present purpose it is
only necessary for me to allude to the membranes, as one of
them, the periosteum, has been held to play a most important
part in the formation and economy of bone.
The periosteum is not so important an element in the
constitution of a bone as has usually been supposed. In the
adult bone, it is nothing more than the fibrous sheath of the
organ, similar to the bounding or limiting membrane of other
organs, and in which the vessels ramify sufficiently to anasto-
mose with those of the comparatively few Haversian canals
which open on the external surface. In the foetus it is much
more vascular, the external surface of the bone being at that
period actively engaged in growth.
4C4 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
There exists in every true bone a membrane or layer of
much greater importance, and infinitely more extended than
the periosteum. Between the bloodvessels and the walls of
the Haversian canals there is a layer of cellular substance.
This cellular substance is the product, its cells being the
descendants of the corpuscles of the cartilage or matrix in
which the bone was originally formed. It forms a blastema,
originally produced round each cartilage corpuscle by
development into a linear series perpendicular to the
ossifying surface : each of the secondary cartilage corpuscles
remaining as centres, or the sources of new centres of
nutrition of the future bone, their progeny forming the
cellular mass which becomes enclosed in the capsules of com-
pact primary bone. When these capsules have opened into
one another to form the Haversian canals, a process similar
to the mode of development of gland ducts and capillaries,
the cellular mass surrounds the vessels in their course, and
separates them from the walls of the canals.
That this cellular layer plays an important part in the
economy of bone, appears probable from the prominent
position it holds in its development, and from the intimate
connection of the Haversian canals with all the morbid changes
of bone. Its existence, great extent, and probable powers,
cannot be overlooked in any question regarding the economy
of bone in health or disease.
The cellular mass, just described, fills the cancelli, or en-
larged Haversian chambers, of foetal bones, and, in this
situation, has not been overlooked by former observers. In
adult bones, it is in the medullary cavity, cancelli, and, to a
certain extent, in the larger Haversian canals, replaced by fat
cells.
On the surface of young and vigorous bones I have
observed numerous cells, flattened, elongated, and more or less
turgid, belonging doubtless to the system of Haversian cells.
REPRODUCTION OF BONE. 465
XXXI THE MODE OF KEPKODUCTION AFTEK
DEATH OF THE SHAFT OF A LONG BONE.
THE question at issue regarding the source of the new osseous
substance in regeneration of the shaft of a long bone, is thus
stated by Professor Syme.* "Whether the periosteum, or
membrane that covers the surface of the bones, possesses the
power of forming new osseous substance independently of any
assistance from the bone itself?" and the Professor has de-
tailed some very ingenious experiments, which satisfied him
that this membrane does possess the power of producing new
osseous texture.
The first experiment consisted in exposing the radius of a
dog, and removing an inch and three quarters of it along with
the periosteum ; and in the other leg removing a correspond-
ing portion without the periosteum. In six weeks the cut
extremities of the radius, from which a portion had been taken,
together with the periosteum, had only extended towards one
another in a conical form, with a great deficiency of bone
between them, and in its place merely a small band of tough
ligamentous texture. In the other, where the periosteum had
been allowed to remain, there was a compact mass of bone,
not only occupying the space left by the portion removed,
but rather exceeding it.
The objection to this experiment is, that it cannot be
performed accurately. I have satisfied myself, that it is
* Trans. Roy. Soc. Edin. vol. xiv. page 158. "On the Power of the
Periosteum to form New Bone."
2 H
466 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
impossible to separate the periosteum from a dog's radius
without removing along with it minute longitudinal, fila-
mentary, or ribbon-shaped portions of the surface of the bone ;
more particularly, as may be conceived, when performed in
the manner which under the circumstances would be adopted,
by slitting it up in front, and detaching it transversely before
separating the portion of bone. It remains to be proved that
it is not from these minute shreds of bone that the regenerated
portion of the shaft has derived its origin.*
In the other part of the experiment, in which the
periosteum as well as the bone was removed, it was not to be
expected that complete regeneration should have taken place,
inasmuch as the bounding or limiting membrane of the organ
had been removed, and the surrounding textures were allowed
to collapse and unite. Even under these unfavourable cir-
cumstances, the cut extremities of the bone had lengthened
themselves out in a conical form.
The two subsequent experiments, by the insertion of tin
plates, though highly ingenious, differ in no essential particular
from the first, and are liable to the same objections. If a
section had been made through the denuded shafts, new bone
would have been found deposited in their interior, just as it
had been at the cut extremities in the first experiments.
The careful examination of numerous bones, the shafts of
which had died, and were in progress of replacement by a
substitute in the form of a shell, has satisfied me that in no
instance do we ever see a new shaft, without at the same time
observing portions of the old shaft ulcerated to a greater or
less extent the ulcerated portions invariably corresponding
in the early stages to the scales of new bone in the periosteum.
Whenever the old shaft is entire, its periosteal surface pre-
senting the natural appearance of a macerated bone, the part
corresponding to this in the new shaft is formed of bone which
* Baly. Note in his Translation of Miiller's Physiology, page 471.
REPRODUCTION OF BONE. 467
is seen to be shooting, in the manner peculiar to this mode of
regeneration, from a point corresponding to an ulcerated
portion of the old shaft. So striking is this peculiarity, that
it will at once recur to those who have had an opportunity of
observing new shafts in an early stage of formation ; as well
as the remarkable contrast between the smooth hard portions
of the dead or dying bone and the nodulated scales lying in
the separated periosteum, alternating with the former, and
concealing from direct view the rough or ulcerated portions of
the dead shaft. In those instances in which the shaft has
died, with the exception of a ring or small portion at each or
one end, close to the epiphysis, the new bone shoots in
stalactitic masses in the longitudinal direction, their course,
direction, and magnitude, corresponding to the forms of the
rings or portions of ulcerated bone in the old shaft. This is
an unfavourable form of necrosis, in consequence of the
difficulty encountered by the extremities of the new shell in
meeting in the centre, and the length of time required for the
process of regeneration. This form has also given rise to a
mistaken view of the source of the new bone in necrosis, a
belief that it is derived from the epiphysis. I have never seen
an instance in which the epiphysis supplied the new shaft,
and I have had occasion to point out that the specimens on
which such opinions were founded are in fact exemplifications
of the formation of the new, from a ring or portion of the old
shaft close to the epiphysis. An epiphysis is a distinct part,
and has no greater tendency to supply the losses of the
principal mass of the bone to which it belongs than the femur,
fibula, or astragalus, to supply the loss of a tibia.
Another remarkable peculiarity, arising from the circum-
stance of the new bone invariably shooting from spots
corresponding to ulcerated portions of the dead shaft, is met
with in instances where one side of a dead shaft is not
ulcerated, and the other side, or a portion of it, has undergone
468 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
that process. In such instances, the new bone proceeds from
points corresponding to the ulcerations, and shoots in the
form of arches across the smooth portion of the old bone,
meeting from either side, and giving rise to new processes
which ultimately enclose the whole. In instances of this sort
regeneration is effected with difficulty, and there is a tendency
in the old shaft to ulcerate out on the side on which it has
supplied no osseous centres of regeneration.
The death of the entire shaft of a long bone must be a
very rare occurrence. In a case of this kind, the shaft would
be found lying loose in a cavity formed by the epiphysis at
each end, and the separated periosteum on the sides. The
bone itself, although its surface might be opened up by in-
flammation, would present no ulceration or actual deficiency
of substance. In a case of this kind, I believe no regeneration
whatever would take place. The epiphyses have no tendency
to assist ; and the periosteum has separated without a single
portion of the shaft from which new bone might be produced.
In the majority of instances of what is incorrectly named
death of the entire shaft, ulcerated portions or deficiencies of the
surface will be met with ; and in the periosteal sheath, scales
of new bone corresponding to these will be perceived. I have
observed the process by which these ulcerations are produced,
and have already described it in the chapter on ulceration.
The first appreciable inflammatory changes in bone occur
within the Haversian canals. These passages dilate or become
opened up, as may be seen on the surface of an inflamed bone,
or better in a section. The result of this enlargement of the
canals is the conversion of the contiguous canals into one
cavity, and the consequent removal or absorption of all the
osseous texture of the part. This removal of the substance
of the walls of the Haversian canals is not to be explained by
pressure arising from effused lymph, understood either in a
mechanical sense, which is inapplicable to actions of this
REPRODUCTION OF BONE. 469
kind, or in the Hunterian sense in which it is employed, as a
mode of expression for an action, the details of which have
not been recognised.
By the enlargement of neighbouring Haversian canals, and
the consequent removal of all the osseous substance of a por-
tion of bone, an ulceration is produced, or a piece of dead or
dying bone is separated from the living organ. A stratum of
what, in the language of surgical pathologists, is named
granulations, divides the dead from the living, and ultimately
casts the dead off, by assuming a free surface towards it,
throwing pus into the inter-space.
When the entire shaft of a bone is attacked by violent in-
flammation, there is generally time, before death of the bone
takes place, for the separation, by the process just described,
of more or less numerous portions of its surface. When the
entire periosteum has separated from the shaft, it carries with
it those minute portions of the surface of the bone. Each of
these is covered on its external surface by the periosteum, on
its internal by a layer of granulations, the result of the
organised matter which originally filled the inflamed Haver-
sian canals ; the gradual enlargement and subsequent blending
of which ultimately allowed their contained vascular contents
to combine with the layer of granulations just described ; and
to form the separating medium between the dead shaft and
its minute living remnants. These minute separated portions,
after having advanced somewhat in development, appear, when
carelessly examined, particularly in dried specimens, to be
situated in the substance of the periosteum, and have been
adduced by the advocates of the agency of that membrane in
forming new bone, as evidences of the truth of their opinions.
In proportion to the equal manner in which these living
portions of the old shaft are arranged over the whole internal
surface of the periosteum, will be the facility and consequent
rapidity in the formation of the new shaft. The shape of the
470 ANATOMICAL AND PATHOLOGICAL OBSEKVATIONS.
new bone will also depend very much upon the same circum-
stances ; for, if the centres of formation of the new shaft are
separated from one side only of the old bone, then an un-
shapely mass of new bone is thrown out on the same side,
for the purpose of strengthening the part during the time
necessary for shooting across the bridges of bone which are to
supply that side of the new shaft, for the formation of which
no osseous centres had been separated. Every possible modi-
fication, resulting from these principles, may be observed in
looking over series of necrosed long bones.
A remarkable fact in connection with cloacae is, that they
are almost invariably opposite a smooth or unaltered portion
of the surface of the dead shaft. They result from the pus
thrown off from the granulating internal surface of the new
shaft making its way to the exterior by those parts not yet
closed, in consequence of having been opposite to portions of
the old shaft, which had not afforded separated osseous
centres. After the new shell has gained its full strength the
cloacae, like sinuses of the soft parts, are prevented from closing
by the continued flow of the pus. The situation of cloacse is
determined by circumstances in the death of the old, and kept
open by the continued flow of the secretions of the new shaft.
As, therefore, it has been found impossible to separate the
periosteum in living animals without detaching shreds of bone
along with it as in necrosis of the shafts of long bones, por-
tions of the old osseous texture may be detected in the
periosteal sheath opposite ulcerations of the dead shaft and
as consistent with what is at present held regarding the
powers of capillary vessels, and the origin of the textures, we
are compelled to assent to the doctrine that periosteum does not
possess an independent power of forming osseous substance.
The participation of the periosteum in the office of regene-
ration an important principle in surgery is not denied in
this conclusion.
VoLll
Plate*
REPRODUCTION OF PARTS IN CRUSTACEA. 47 1
XXXII. THE MODE OF EEPEODUCTION OF LOST
PAETS IN THE CEUSTACEA. (PLATE IX.)
THAT all the species of Crustacea have the power of regene-
rating parts of their body which have been accidentally lost,
is a fact which has been long known. The particular manner
in which these new parts are developed, and also the organ
from which the germ of the new part is derived, has never
yet been sufficiently examined or properly explained.
If one or more of the last phalanges of the leg of a
common crab be seriously injured, the animal instantly
throws off the remaining parts of the limb close to the body.
It has the power of doing so, apparently for two purposes ;
to save the excessive flow of blood which always takes place
at the first wound, and to lay bare the organ which is to
reproduce the future limb. As soon as the injured limb has
been thrown off the bleeding stops, the reason of which will
be explained hereafter ; but if the animal is unable, from
weakness or other causes, to effect this, the haemorrhage
proceeds to a fatal termination.
It is apparently in the organs of locomotion only that
the power of reproduction resides. That it does not do so in
all parts of the body in the higher Crustacea, at least is
proved by experiment, and is also apparent from the circum-
stance of many species being obtained with the body and
other parts very much maimed, and which have to all
appearance been so for a considerable period. Wounds of the
body in general prove speedily fatal, if they penetrate deeply,
472 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
but if otherwise, a cicatrix only is formed, which remains
until the casting of the shell, when the new shell takes on
all the characters and appearance of the old one, before it met
with the injury. When the animal is weak and unhealthy,
and in that state meets with any severe injury of a limb, it
is unable to throw it off at the usual place, and consequently
very soon dies from loss of blood ; but when strong and
vigorous, it is enabled to throw the injured limb off with
little apparent pain or exertion. It is a well-known fact,
that these animals can throw off their limbs when seized by
them, and also from several other causes, to which it is
unnecessary to allude at present.
When the crustacean does throw off a limb voluntarily, it
will be found on examination that this is always effected at
one spot only, near to the basal extremity of the first phalanx.
This part of the phalanx is very much contracted for the
length of half-an-inch, or a little more, in the common edible
crab. The whole of this portion is filled with a fibrous,
gelatinous, glandular-looking mass ; the organ which supplies
the germs for future limbs. On looking closely into the
surface of this body, we find that it is divided into two
unequal parts, by means of a transverse line. The basal or
proximal part of this body is the smallest. On tracing this
line towards the shell we find that it runs into it, as it were,
and forms, instead of one line, two ; by which means a very
thin ring is formed, and this ring is also found to run com-
pletely round the limb, being marked externally by means of
a thin band of small scattered hairs. By dissection this line
can be traced into the substance of the organ of reproduction,
and is found in this way to be the exact spot where the limb
is generally thrown off. Through the long axis of this, and
near to one edge, a small foramen exists for the transmission
of the bloodvessels and nerve. The microscopic structure of
this gland or organ is extremely beautiful. When a thin
REPRODUCTION OF PARTS IN CRUSTACEA. 473
transverse section is made, and placed under the microscope,
it is found to present the following appearances : The
foramen, for the transmission of the vessels and nerves, which
was distinctly seen with the naked eye, is obscured on
account of the pressure arising from the glass plates, but its
situation can be still distinctly made out near to one edge
of the section, and also within a thick fibrous-looking band,
which, when traced, is found to surround a considerable
extent of surface. The space contained within this band is
also found upon examination to be much more transparent
than that beyond it, and to contain numerous small cells, all
of which have nuclei or nucleoli within them. These cells
appear to be suspended in a thickish transparent liquid. The
thick fibrous band, mentioned above, is composed of a great
many fibres, all of which run almost parallel to one another.
Beyond this band, and occupying the remaining space between
it and the shell, lies a confused mass of large primitive cells
or blastema. The shell membrane, covered by the shell,
encircles this, thus the whole structure of the leg at this
part consists of, 1st, the foramen for the transmission of the
vessels and nerves ; the fibrous band, with the semi-liquid
mass containing small cells ; the blastema of larger nucleated
cells ; and, lastly, the shell membrane, covered by the shell.
In reference to the fibrous band here mentioned, farther
observations have proved it to belong to a very peculiar
system of vessels, which are very generally distributed
throughout the body of the animal. They ramify very freely
over the membrane lining the carapace, throughout the ovaries,
liver, intestinal canal, and on the bloodvessels of the organs
of locomotion. In the latter, they are arranged at regular
intervals, and run parallel to one another. They run in this
manner, until that part of the leg is reached about half an
inch beyond the reproductive gland, when they terminate by
means of blind extremities. I have not yet made out the
474 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
exact relative anatomy of this very peculiar system of vessels,
or in what manner those running in the longitudinal direction
of the leg are connected with the circular one which sur-
rounds the foramen at the point of fracture, but immediately
after the animal has thrown off the injured limb, the raw
surface becomes covered with these vessels. Before the
separation, the vessels had been partially empty ; but imme-
diately on the separation taking place, they became so
distended as to become visible to the naked eye. In all the
observations made, it was generally found that these vessels
presented a radiated appearance on the newly made surface,
running from the circumference to the circular one sur-
rounding the situation of the germ. The greater number also
appeared to terminate at the circumference by means of
blind extremities. A dark circular disc was seen at the
extremity of many of these cul-de-sacs, which had all -the
appearance of a germinal spot. When these vessels were
first seen, they were thought to be connected with the re-
productive gland alone, but after further observations, this
appeared to be incorrect; and, as already mentioned, their
relations are so extensive and complicated as to require much
more time for their elucidation than I have had since they
came under my observation. It is evident, however, they
perform some important function in the economy of the
animal, but whether it is connected with the reproduction of
lost parts or not, is a question to be decided by future obser-
vation.
Immediately on the limb being thrown off, a quantity of
blood escapes, which is soon stopped by the retraction of the
vessels. After this takes place, we see the small open foramen
for the passage of the artery and nerve, which becomes closed
almost immediately by means of a slight film which spreads
over the whole of the exposed surface. When this surface is
examined some hours after the loss, we find that the small
REPRODUCTION OF PARTS IN CRUSTACEA. 475
cavity of the foramen is slightly filled up with a body resem-
bling a nucleated cell. This cell is the germ of the future
leg, and very shortly increases in size, so as gradually to push
out the film alluded to above, which is now become a thick
strong cicatrix. During the time that this is going on, the
whole of the exposed surface had become tense and bulging,
but this gradually decreases round the circumference as the
central nucleus increases in size, which it does at first longi-
tudinally, and then transversely. As it increases in size, the
cicatrix, which still surrounds it as a sac, becomes thinner and
thinner, until it bursts, when the limb, which has hitherto
been bent upon itself, becomes stretched out, and has all the
appearance of a perfect limb, except in size.
In the lower Crustacea, and even in the lower Macroura,
we find the power of regeneration more extended ; a limb
broken off at any part of its phalanges will grow. The mode
of reproduction in the lobster is peculiar, and differs from the
higher Crustacea. Instead of the young limb being folded
upon itself, as we found it in the Brachyura, it is quite
extended, although apparently enclosed in a sac.
As far as my observations have yet gone, it appears to me
that the germinal cell is derived from one of those which are
nearest the central opening on the raw surface. This cell,
following the ordinary course of development, by the nucleus
breaking up into nucleoli, which in time become parent cells,
each of which again undergo the same process. This proceeds
for several stages, all the less important cells dissolving and
serving as nourishment to the central or more important ones,
until the number of centres are reduced to five, the number of
joints required, which, by a constant process of a similar nature,
assume the form of the future leg. H. D. S. G.
476 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
XXXIII. OF THE ANATOMY AND DEVELOPMENT
OF THE CYSTIC ENTOZOA .* (PLATES VI. X. XI. XII.)
I. OF THE ACEPHALOCYST.
THE acephalocyst, or simple hydatid, consists of a vesicle com-
posed of several membranes containing a quantity of fluid, in
which, the young hydatids float, and from which they ap-
parently derive nourishment.
Although found in all parts of the body, these animals are
nevertheless more strictly confined to the liver, which appears
to be their natural habitat.
In examining an acephalocyst from without inwards, there
is met with, first, the natural tissues of the infested being
slightly condensed, the condensation being greatest near the
hydatid, and becoming gradually less as the distance increases.
The next part met with in the dissection inwards, is a strong
fibrous membrane, of considerable thickness, with numerous
bloodvessels. This forms a sac for the hydatid. During the
earlier stages of growth, hardly a vestige of this can be seen ;
for being formed of the condensed tissues of the infested
animal, it becomes perceptible only after the parasite has
attained some size. It is highly vascular, and forms a cushion,
to which the external surface of the hydatid is applied. In
this way, a steady supply of the blood, or of debris of the
textures of the infested animal, is close at hand, from which
the hydatid may extract nourishment. This membrane is
best seen in aged hydatids, or in those in which the process
* Read before the York Meeting of the British Association, 1844.
VoLJI
Plate X
'
THE CYSTIC ENTOZOA. 477
of obliteration has commenced, and in such can easily be de-
monstrated by dissection. In such aged individuals also it is
found to be so intimately attached to the external membrane
of the hydatid, as to appear to form one membrane with it ;
whereas in younger individuals a considerable space inter-
venes.
The external coat of the hydatid is gelatinous and slightly
fibrous in appearance, and presents no structure.
The middle membrane appears to be of the nature of a
germinal membrane, is much thinner, and more delicate than
the external membrane. In this membrane numerous cells,
in various stages of growth, take their rise, and project inwards
into the cavity of the hydatid, carrying the next membrane
along with them.
The internal membrane does not appear to be continuous
over the whole internal surface ; but observed only where it
is reflected, as has been just stated, over the surface of the
germinal cells. It may, therefore, be considered as that por-
tion of the middle or germinal membrane which has been
carried inwards by the rise of the germinal cells in the sub-
stance of the former membrane.
A small clear cell or vesicle, jutting from the internal
surface of the second membrane, is the first vestige of the
young hydatid. At first this vesicle is colourless, but as it
increases slightly in size, it becomes opaque, and also carries
the internal membrane inwards before it, which in time, as
the young hydatid becomes more pedunculated before becoming
free, almost covers it entirely. Vestiges of this membrane
may be seen attached in shreds to the vesicle, even after it
has attained a considerable size.
In all the hydatids which have already become independent
animals, with their external coat still gelatinous, and are still
enclosed within the cyst of the original acephalocyst, it may
be observed that one side presents shreds of membrane
478 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
attached to it ; but that the other is quite free and almost
transparent. This transparent part was that originally
attached to the parent or germinal membrane ; and the shreds
are consequently the remains of the internal membrane of the
parent. Shortly before the young hydatid separates from the
germinal membrane of the parent, smaller cells are seen with-
in it, which increase in size along with it. These are another
generation of hydatids, and the fourth in the series I have
been describing.
About this period in the process of development, there may
be seen in some forms of hydatids of the tertiary growth, a
dark irregular flat nucleated spot, which always occupies the
same place, immediately opposite that of attachment. This
spot is visible only before the separation. I am inclined to
consider this spot as the first appearance of the pedicle, or
what is generally termed a head in the class. This species I
denominate Aceplialocystis armatus. This appearance is merely
the nucleus or central cell, from which all the others are pro-
duced ; thus illustrating that the pedicles of Csenurus and
Cysticercus are analogous to this nucleus, both being repro-
ductive organs ; in the acephalocyst being a reproductive
organ only, in Csenurus and Cysticercus being chiefly a repro-
ductive organ with a slight adaptation for the purposes of
prehension.
If the small cells which are seen in the tertiary hydatids
are the young, they must be the first of those which are after-
wards seen attached to the germinal membrane, for I have not
met with secondary hydatids enclosing separated young indi-
viduals. It is only after the hydatid has obtained a nidus, or
separate habitat of its own, that it begins to throw off its
young from the germinal membrane, and those only which
had been formed during the tertiary and secondary periods.
Thus, if the original hydatid is buried deep in the textures of
the infested being, or from other causes is prevented giving
THE CYSTIC ENTOZOA. 479
exit to its young (for it is by the dilatation caused by the
young within it that the parent sac gives way), it soon becomes
unable to extract proper nourishment from the infested being,
the young within it become decomposed, and the whole animal
degenerates either into a firm cicatrix, or, as is most general,
into a fatty cretaceous matter. I have in many instances
found this matter forming upon the external coats of young
secondary hydatids, which were confined, as above stated, in
old and degenerating parent sacs. In general this cretaceous
matter originates in the internal and germinal membrane of
the parent sac ; these two membranes in old hydatids being
always thick, gelatinous, and homogeneous, like pure gelatine.
This thick gelatinous membrane presents no trace of the two
membranes of which it originally consisted ; it is generally
about the eighth of an inch in thickness, and lies in the most
dependent part of the cavity, quite loose and detached from
the external coat. It presents no trace of young vesicles or
hydatids, but has upon its internal surface a number of white,
opaque, fatty looking spots of all. sizes. Similar spots, but of
much smaller size, are also to be seen in the substance of the
membrane, and when examined by the microscope, present a
peculiar cellular network. As these spots become larger, they,
from being quite smooth, become rough and nodulated, each
of the cells being apparently filled with the peculiar fatty
substance. As this mass increases in size, it becomes more
cretaceous, and sends out branches in all directions, so as in
time to fill the whole cavity of the hydatid, which, as this
process is going on, shrinks up very much, so that it meets
the fatty matter, and enables the process of filling up to be
more speedily completed. Shortly before the cavity is com-
pletely filled up, the fatty matter begins to lessen in quantity,
being probably absorbed by the cretaceous matter gaining the
preponderance. In this way more or less of the whole mass
is absorbed, so that ultimately nothing is left but a small
480 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
quantity of cretaceous matter which becomes very much
condensed.
The middle membrane then appears to play the most im-
portant part in the economy of the hydatid ; the external
membrane acting only as an organ of defence.
Of this peculiar form of animal three species have been
determined, the characters of which are derived from the
structure and appearance of the germinal membrane. In
AcepJialocystis simplex, the lowest of these forms, the whole
structure of the animal is much more homogeneous, trans-
parent, and gelatinous, than that of the two higher forms ; the
cyst is not divided into separate parts, and the young are
developed promiscuously throughout its internal surface.
In AcepJialocystis armatus, the young are developed from
a true germinal membrane, each of the young arising as a
separate cell, and afterwards throwing off internally successive
broods of young independently. It is also distinguished from
the other species by the teeth which it possesses during the
period of its attachment to the parent germinal membrane.
These teeth are generally exactly opposite the spot of attach-
ment, are quite straight, barbless, and form an irregular
circlet, somewhat similar to that of Csenurus and Cysticercus.
They are lost as soon as the animal leaves the germinal
membrane and becomes free, and not the slightest vestige of
them can be seen, even upon the shreds of membrane alluded
to above, which at one period formed the internal membrane
of the parent sac.
In the Medical Gazette for Nov. 22, 1844, p. 268, there is
an abstract of a paper read before the Koyal Medical and
Chirurgical Society of London, by Erasmus Wilson, on the
" Classification, etc., of Echinococcus hominis" There can be no
doubt that the Echinococcus here described by Mr. Wilson,
and the AcepJialocystis armatus, are both one and the same
species. The bodies described by Mr. Wilson as the
THE CYSTIC ENTOZOA. 481
echinococci, and which are attached to the internal surface of
the membrane, are merely the young acephalocysts either of
the secondary or tertiary stages of development. They will
be, as already fully described in this paper, of the secondary
generation, if found growing from the walls of the original
containing sac, and tertiary if found growing from the walls
of those sacs floating free in the fluid contained within the
original sac. This animal is an acephalocyst, and not an
echinococcus. Bremser, in the atlas of his work, On the,
Intestinal Worms of Man, calls it an echinococcus, but upon
false grounds, for the proper definition of echinococcus, he
says, at p. 294 of his work alluded to :* "M. Eudolphi dis-
tingue les hydatides en vivantes et en non vivantes ; il regards
1'echinocoque proveriant des intestins des bisulques (Echi-
nococcus veterinorum) comme une hydatide vivante, par la
raison que Ton trouve dans le liquide qu'elle contient les ec-
hinocoques, proprement dits, c'est-a-dire, des petits corps mi-
croscopiques, pourvus de quatre su9oirs et d'une couronne de
crochets." The animal described by Mr. Wilson is also
referred to in the same abstract by Dr. Budd, " who examined
seven hydatid tumours which had been for many years in the
Museum of King's College," when he found appearances
exactly similar to those described by Mr. Wilson. It is more
than probable that the animals here alluded to by Dr. Budd
are similar to that I have called AcepJialocystis armatus, which,
if the case, from the want of suckers, cannot be an Echi-
nococcus, being merely a transitory stage of the acephalocyst.
For I have examined great numbers of these animals, pre-
served in the Museum of the Eoyal College of Surgeons in
Edinburgh a collection particularly rich in preparations of
these animals and in no instance have I been able to make
* Traite Zoologique et Physiologique sur les Vers Intestinaux de I'Hmnme,
par M. Bremser. Traduit de I'Allemand par M. Grundler. Revu et augmente
de Notes par M. de Blainville.
2i
482 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
out the slightest vestige of suckers. I had made out the
existence of teeth, and was anxious to determine whether or
not the animal was allied to the cephaloid hydatids.
The next form of Acephalocystis is one presenting a
structure peculiar to itself, and which at once distinguishes it
from the others. The external membrane is gelatinous and
delicate ; the germinal one is more fibrous, and is so slightly
attached to the external one as to float in the contained fluid.
When a small portion of this germinal membrane is placed
under the microscope, its free or internal surface presents the
following appearances : 1st, A fibrous texture forming the
basis of the membrane ; 2d, A series of large irregular ovoid
vesicles, arranged in irregular rows. The fibrous texture sur-
rounds the vesicles, and thus presents a peculiar appearance
of ramification of a very regular form. Each of the vesicles
contains one or more dark spots containing nucleoli these
spots are the young hydatids.*
ii. OF ASTOMA. (PLATE XT.)
Astoma acephalocystis is an animal very nearly allied to
Acephalocystis.f It was found attached to the peritoneum
of an old subject, generally by means of a broad basis, but
very often by a slender pedicle. The sac, composed of three
membranes, of more or less delicacy, was very strong, and the
membranes were easily separable from one another. They
were all more or less composed of fibrous texture, and, as in
the Acephalocystis, the external appeared to serve as a means
of defence, while the two inner were devoted to nutrition and
* This species I have named Acephalocystis Monroii, after Dr. Monro, to
whom I am indebted for the opportunity of examining the species, and from
whom also I have received much valuable information regarding hydatids
generally. A very beautiful figure of A. Monroii is given in Dr. Monro 's work
on The Morbid Anatomy of the Stomach and Gullet.
f Edinburgh Medical and Surgical Journal, No. clxi., p. 14.
VofJf
PlateXI
THE CYSTIC ENTOZOA. 483
generation. The young cells, after acting for a time as the
organs of nutrition, become free and independent animals after
having thrown off young cells internally, which in their turn
act as organs of nutrition to their parent until they are fit to
become independent animals themselves. The particulars
relative to the peculiar mode of development of ths aniimal
will be adverted to more at length when we come to treat of
that function in Diskostorna ; in the meantime a few remarks
on the external character of the animal may be useful.
It was of a greenish yellow colour when taken from its
habitat, and varied in size from a millet seed to that of a
middle-sized orange. The smaller specimens were all spheri-
cal, and very much corrugated ; the larger were quite smooth
and botryoidal the first of which appearances arose apparently
from the distension caused by the young ; the second, from
the young within it increasing irregularly in size. When a
section was made of an adult specimen, the interior was found
to consist of an immense number of young in various stages
of advancement, and all of them apparently having their
origin from the inclosing sac, either immediately or mediately.
Along with these the interstices contained a great quantity of
gelatinous matter, which appeared to be the assimilated food,
analogous to the pabulum of the seminal cells already spoken
of in another paper.
III. OF DISKOSTOMA.* (PLATE XI.)
Diskostoma acephalocystis is another animal belonging to
the Cystic Entozoa, and very similar in many respects to the
preceding genera ; it is, however, more complicated in its
structure than either.
Diskostorna was met with in great numbers in the peri-
toneal cavity of a middle-aged man. About six or eight
* Transactions of the Royal Society, Edinburgh, vol. xv., p. 564.
484 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
gallons were taken out of the abdomen after death, all of
which had been apparently generated in the course of a few
months. * Like Astoma they varied very much in size, but,
with very few exceptions, were all regularly globular and of
a bright straw colour, hanging, when undisturbed, from the
surface of the abdominal cavity like the ova in the active
ovarium of the common fowL The sac consisted of two de-
monstrable membranes, the most external of which was rather
complicated.
The basis of the membrane itself was fibre-gelatinous, and
having a number of discs scattered at irregular intervals over
its surface ; these discs were connected with one another by
means of numerous tubuli, which also ramified freely through
the membrane. These were probably the organs of nutrition.
The next membrane was much more delicate, and was that
from which the gemmules arose. In some instances there
was the appearance of a third membrane, but it was most
difficult of detection. The greater mass of the body was com-
posed of the gelatinous matter already alluded to as occurring
in Astoma.
The function of generation in all these lower Acephalocysts
is very interesting. In all of them the young cells or gem-
mules arise from the middle membrane of the sac. In Ace-
phalocystis and Astoma the young cells act at first as organs
of nutrition, and after a time become themselves independent
animals. This is probably the case in Diskostoma also, but
it could not be determined with certainty. The mode of de-
velopment of the young in Astoma and Diskostoma is some-
what different from that already described as taking place in
Acephalocystis. There appear to be two modes of generation,
namely, one for the enlargement of the original group, and
another for the formation of new groups in other parts of the
peritoneum. The first of these modes proceeds in the Astoma,
* See Edinburgh Medical and Surgical Journal for October 1844, p. 1.
THE CYSTIC ENTOZOA. 485
from the animal becoming so distended, in consequence of
the increased size and number of the young within it, that it
bursts when the young are exposed, and the parent sac, which
is now useless, absorbed, the progeny in the meantime becom-
ing attached to the peritoneum.* The external membranes in
Diskostoma spread over the, as yet, uninfested portions of the
peritoneum, and give origin to a number of cells from the
attached surface, each of which, becoming parents, gradually
increases in size, from the addition of new matter within the
young cells. These young cells are the germs of the future
animals. The other mode of development, or that intended
for the formation of new groups, is similar in both animals.
The young or secondary cells, bursting from their formative
cell, by some means escape from the parent sac, and so gain a
situation at some distance from the original group, where they
become attached, in time throw off young cells, and thus be-
come the origin of a new set.
Eelative to the mode of reproduction in these animals, it
is found that in Astoma, and the higher cystic entozoa, the
numbers proceeding from one parent may be unlimited,
whereas in Acephalocystis, generation ceases with the quater-
nary series of young, unless this series, or the gemmules of
some of the preceding, escape from the original sac and are
able to form a nidus in any portion of the liver, or other
organ yet uninfested. For it appears necessary to the exist-
ence of the common hydatid that it be completely enveloped
in the tissues of the infested being. To ensure this normal
habitat, then, the animal must escape during the period of its
gemmule existence from the parent ; but, as most generally
happens, if the parent hydatid be so deeply buried as not to
allow free rupture of its coats within a certain period, decom-
position ensues as already described, and so existence is
* See Preparation in Mweum of Royal College of Surgeons, Edinburgh,
No. 2244.
486 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
terminated ; if, on the contrary, the parent hydatid be so
near a surface, or from other causes, as during its increase in
size to rupture, then the young escape, and so form new and
altogether independent animals. As the hydatid is by no
means of unfrequent occurrence in the liver and other internal
organs, this limitation of the increase appears to be a benefi-
cent law of nature, for the purpose of preventing the fatal
termination which the rapid increase of these animals would
infallibly produce. In Diskostoma we have an instance of
this rapidity of reproduction, which happily appears to be of
rare occurrence.
It may be well to state here also the opinions to be deduced
from the changes which take place in the germinal membrane
of Acephalocystis, and the other acephalic entozoa. It has
been already fully described in what manner the function of
reproduction in these animals is stopped, namely, in con-
sequence of the thickening of the germinal membrane. After
having made out this fact, I was led to infer that many
instances of the stoppage of cellular formations at certain
periods of life might be traced to similar changes taking
place in the germinal membrane of the formative organ, and,
with the view of determining this point, examined the testes of
several old men, after the fecundating power had in all
probability passed away, when the germinal membrane in
almost all cases had become thicker and quite different from
what is generally seen in young males, a change which (as
we have attempted to describe) had taken place in the
germinal membrane of hydatids.*
* The stoppage here alluded to, in the function of reproduction of these
animals, may be also greatly assisted, and the degenerating process made more
active, in consequence of the thickening of the external membrane preventing
the absorbing cells extracting from it a sufficient supply of nourishment.
VoLJl
THE CYSTIC ENTOZOA. 487
IV. OF SPHAIRIDION.* (PLATE VI., FlG. 16.)
Sphairidion acephalocystis is an animal allied to Acephalo-
cystis, chiefly from its acephalic character, but also from its
reproductive organ being enclosed within the centre of its sac.
This reproductive body or membrane is exactly similar to
the pedicle of the Cysticercus, with the exception of its being
entirely buried in the body of the animal, consequently also
it is neither furnished with teeth nor suckers. There is no
separate absorbent apparatus in the sac of the animal, and
this part of its body appears to be composed of one membrane
only, which is analogous to the external membrane of the
sac of Acephalocystis. The cyst of this animal at first
appears to be composed of three membranes, but a little
examination proves the outermost to consist of peritoneum
only, the two others being similar to the analogous membranes
of the cyst of Cysticercus rattus, namely, an external for
defence, and an internal for absorption of nourishment.
This animal was found attached to the intestines of the
Balearic Crested Crane (Balearica pavonia, Vigors) beneath
the peritoneum.
V. OF C^ENUEUS.f (PLATES VI, XII.)
The next animal we have to describe is Caenurus. It is
in the species belonging to this genus that the first vestiges
of extremities are perceived, to which form of* structure we
are ]ed through Diskostoma the discs described in the latter
being without doubt analogous to the pedicles of the
Caenurus.
Ccenurus cercbralis, an animal frequently found in the
brain of the sheep and other ruminants, has been long known
* 2<f)ai.pi5iov, a globule.
t Transaction* of the Royal Society, Edinburgh, vol. xv. p. 564.
488 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
to naturalists. This animal is composed of a double sac
from the external surface of which proceed a number of small
bodies, termed pedicles. These pedicles are contained between
the two membranes of the sac, project at right angles from
its surface, and are armed at the extremity with a double
circle of teeth.
The sac of the Caenurus is composed of two membranes,
the outermost of which acts as an organ of defence, the
internal, containing a layer of absorbent cells, acts along with
the larger cells contained in the pedicles as organs of
nutrition. The natural size of a pedicle is about the one-
eighth of an inch in length. It is divided into two parts, the
basal and distal. The former contains the absorbing cells
already spoken of, which, after a time, become themselves
independent pedicles. The cells within the pedicle are
arranged regularly in the form of concentric circles, each cell
as it becomes a parent forming a centre. The latter, or distal
portion of the pedicle, contains very few, if any, of these
cells, but bears on its extremity a double series of bent
barbed teeth, which enable the animal to attach itself firmly
to the infested body. Four suckers are also placed at regular
intervals round the sides of this portion of the pedicle.
When one of the smaller cells escape from the pedicles
and obtains a situation between the layers of the parent sac,
it shortly commences to take on a new action, the nucleus
enlarges and presents a clear spot in the centre. As this
spot increases in size, the nucleus becomes irregular on its.
edges, and shortly becomes nodulated, the nodules after a
time are thrown off as separate cells, a central cell occupying
the place of the clear central spot.*
This is the termination of the first stage of the develop-
* The great similarity which exists between the development of this animal
and the mammiferous ovum, as described by Dr. Martin Barry, will be
noticed by all observers.
THE CYSTIC ENTOZOA. 489
ment of the ovum, after which the nucleus of the central cell
undergoes a similar process, the cells proceeding from it
pushing out nearer to the circumference those of the previous
generation. Thus we have a great series of centres, round
which all the other cells are arranged in circles. This I have
termed the discoidal period of development.
After numerous circles have been thus formed, the cells
nearest the circumference, and, of course, those first formed,
become parents, and consequently centres ; but a few of these
gaining the advantage, dissolve the more peripheral cells and
absorb them, thus becoming principal centres. As soon as
this change in the development has taken place, the mode of
growth, hitherto discoidal, becomes vertical, or at right angles
to the sac, and so proceeds until the pedicle becomes perfect.
There is still another animal belonging to this series, and
which requires to be noticed in this place. It is nondescript,
and its characters resemble so much both those of Acepha-
locystis and Csenurus that I have not yet been able to decide
with precision to which genus it belongs. It has certainly
more of the characters of the Csenurus than Acephalocystis,
although many also connect it most intimately with the
latter. In the meantime, however, I have placed it along
with Csenurus, and from its habitat called it C. hepaticus.
In all its more important characters, it is very similar to the
C. cerebralis.
VI. OF CYSTICERCUS. (PLATE XII)
Cysticercus is distinguished from Caenurus by its sac
having only one pedicle ; it is also always contained in a cyst,
which, in some cases, is formed from the compressed textures
of the infested animal, while in others it consists of two mem-
branes, viz., one similar to that mentioned, and another, sui
generis, and belonging entirely to the parasite. The pedicle
of the Cysticercus is exactly similar in its structure to that of
490 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
the Coenurus, with the exception of the cells, which are not
arranged so regularly. The sac is also composed of two mem-
branes, each having structures exactly similar to that of the
Caenurus.
I have divided the animals composing this genus of
Entozoa into two classes, in consequence of the difference of
structures met with in the cyst. Those species, in which the
cyst is only composed of one membrane, derived from the
compressed tissues of the infested being, have been placed
near to the Acephalocysts ; and those in which the cyst con-
sists of two membranes already described, compose the other
division.
The Cysticercus cellulosus is an example of the first of these
divisions. In this animal the cyst is very vascular, i.e. more
so than the surrounding textures, so that in this respect it is
quite similar to the analogous structure in Acephalocystis.
As an example of the animals belonging to this division of the
genus, there is another species which appears to be nonde-
script. This Cysticercus was found in the Museum of the
Royal College of Surgeons, but unfortunately the jar was not
labelled, so that I am uncertain from what animal it was got.
It is enclosed in a cyst formed by the omentum alone ; these
cysts are pedunculated, and although quite continuous with
the healthy portion of the membrane, it is so puckered and
constricted at the pedunculated portion as to be quite im-
permeable, so that the enclosed animal can obtain no nourish-
ment from without, except through the portion oi omentum
forming the cyst. The cyst is very vascular, and generally
contains a quantity of thin granular looking matter (probably
the matter intended for the food of the enclosed animal). The
double circlet of teeth in this species is remarkable for their
great length. In many specimens which came under my
notice numerous small globular bodies were observed, sur-
rounded externally with hooked spines, and attached to the
THE CYSTIC ENTOZOA. 491
internal surface of the cyst, apparently by means of the spines.
These bodies, although the intermediate stages between them
and the young gemmules could not be seen, I considered to be
young Cysticerci in an advanced stage of growth, and I was
led to do so because they were often observed on the free
surface of the omentum, attracting and puckering it together
in folds, evidently the commencement of the process for the
formation of a cyst, and in many instances they had completely
enveloped themselves. It has not yet been decidedly made
out in what manner the gemmules escape from the body of
the Cysticercus, but from the observations I have made, it
appears that they must first escape from the pedicle where
they are formed into the sac, and then from the sac to the
cyst. I am led to this supposition in consequence of having
observed on several occasions the sac of the animal ruptured,
and great numbers of the globular spined bodies attached to
the inner surface of the cyst. How they escape from the cyst
I have not been able to determine.
Those Cysticerci having the cyst composed of a double
membrane, do not differ in any other particular from those of
the preceding division of the genus. The best example of this
peculiarity of structure exists in a species found in the liver
of the rat, and which I have denominated Cysticercus rattus.
The specific characters are given in the synopsis at the end of
the paper.
In all the details, then, we find a great similarity between
Csenurus and Cysticercus, with this exception, that the latter
is simple, whereas the former, like all the other Acephalocysts,
is a compound animal. Why the pedicles of Csenurus should
all become attached to the same sac, is a fact, the cause of
which it will be impossible to determine with any degree of
certainty ; probably, however, it arises from the difference of
strength in the sacs of the two animals ; the greater strength
of that of Caenurus preventing the escape of the young gem-
492 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
mule from between its membranes. The mode of formation
of the sac is also a point interesting to the physiologist, and
one deserving consideration. In Acephalocystis and the other
allied genera, the original gemmule, shortly after it has become
an independent animal, begins to swell out and be distended
from the accumulation of new matter within it. This new
matter is drawn into it by means of the young internal cells
which have just been formed, and which have a power, in-
herent in themselves, of attracting and assimilating nourish-
ment from without. The cells referred to here are the young
germs of future hydatids, and which afterwards, as already
explained, become independent animals ; but, at the same
time, there is in many cases also another series of cells, whose
only function is to act in this way, and throughout the term of
their existence : these have been termed absorbent cells.
Now, these cells drawing in the nourishment in this way
cause the expansion of the original cell-wall, so that the en-
largement of these bodies resembles a process of dilatation.
This, then, appears to be the explanation of the peculiar forms
assumed by the Caenurus and Cysticercus, as well as the
different species of acephalocysts ; that it is so can be proved
from Sphairidion aceplialocystis, an animal very nearly allied
to Caenurus, and being a connecting link between the acephalic
and cephalic hydatids ; for in this animal we find that portion
of its body analogous to the pedicle of Cysticercus, not exserted,
as in the latter animal, but situated in the centre of the body,
where it forms the attracting point for the nourishment
absorbed, which accordingly dilates the external and con-
taining sac.
What I wish to be inferred from this is, that the sacs of
Acephalocystis, Caenurus, and Cysticercus, are analogous
organs ; and that the pedicles of these two latter animals are
analogous to the reproductive nucleus, which may be observed
during certain early stages of the development of Acephalo-
THE CYSTIC ENTOZOA. 493
cystis, as well as the reproductive and absorbing nucleus of
Sphairidion.
Species of Cysticercus have been found in almost every
part and cavity of the human body. In the brain, eye, lungs,
liver, in the walls of the intestines, and in the muscles. In
the present state of our knowledge, it is impossible to say
how these animals gain such habitats as the eye, etc. This
is a question, however, which has been the cause of much
discussion.
VII. OF THE HIGHER CYSTIC ENTOZOA.
Besides those already described, there are many other forms
of entozoa of the higher orders, which are inhabitants of cysts
similar to these of Cysticercus ; we have examples of this
occurring in the Nematoidea, Cestoidea, and Acanthacephala,
etc. As examples of the worms alluded to, I may instance
Trichina spimlis, Gymnorliynchus horridus, and a small filaria
inhabiting the livers of some fish, but, as far as can be made
out, not hitherto described by any author. As another ex-
ample, too, of these peculiar forms, may be mentioned, a very
interesting animal which will be afterwards described, namely,
Neuronaia Monroii.
The cysts of all these worms have similar structures to
those of Cysticercus, namely, an external membrane composed
of compressed cellular texture, and an internal membrane con-
taining absorbing cells, through which the contained animal
obtains nourishment.
In the descriptions of the Acephalocysts already given, it
will be remembered how the animal died in consequence of
the thickening and hardening of the external membrane of the
cyst, preventing the absorption of nourishment from or through
it ; so in like manner do these higher Cystic Entozoa Trichina
die from a similar cause. In many cases where the subject
is infested with Trichina, it is found on examination, that with
494 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
few exceptions almost every specimen is converted into the
hard cretaceous matter spoken of ; many, at the same time,
presenting all the intermediate stages of decay. Gymno-
rhynchus presents us with a very curious habit dependant
upon this mode of structure, and which enables the animal to
avoid the death from which all its co-geners suffer. This
species, which I have fortunately had an opportunity of ex-
amining in its natural habitat, but which has been already
described by my brother (Edinburgh Philosophical Journal,
vol. 31), inhabits the liver of the sun-fish in great numbers,
and from its peculiar structure is enabled to move slowly
through the organ it infests. If the cyst of this worm is
carefully examined, it will be found that the inner membrane,
containing the absorbent cells, is covered anteriorly with a very
thin layer only of the external membrane, so that it is enabled
to absorb the nourishment from the external textures in great
abundance, which thus enables the animal to move forward as
well as obtain a supply of food ; as we trace the cyst back-
wards, the external membrane will be found to become thicker
and thicker, as also more impermeable, until we reach the tail
of the animal, after which it becomes a mere cord. This cord
can be traced for a great distance, becoming less and less per-
ceptible, until it is lost altogether, and the course only marked
by a simple line of a darker colour than the rest of the textures.
It will be observed that the external membrane of this animal
presents analogies similar to that of Acephalocystis ; for in-
stance, the cephalic portion of the membrane is so thin as to
be hardly distinguishable, being thus analogous to the young
hydatid.
In regard to the cyst of these worms, it has been long a
question how far it is a part of the enclosed animal. Professor
Owen* holds that it is merely condensed textures of the
* Owen, "Description of a Microscopic Entozoon infesting the Muscles of
the Human Body." Transactions of the Zoological Society, vol. i. p. 322.
THE CYSTIC ENTOZOA. 495
infested being, and Dr. Knox* again, that it belongs essentially
to the parasite. My brother, in the paper already alluded to,
says, regarding the cyst " May we not suppose them to be
parts of the original ovum, within which the animal was formed,
and within which it passes its term of existence." From ob-
servations made on the development of the Acephalocystic
entozoa, it may be safely stated, I think, that the above state-
ment is correct, for Acephalocystis must be considered as an
enlarged ovum ; but Sphairidion perhaps is the best example
of this peculiar mode of formation, the "inserted pedicle" being
analogous to the confined Trichina or Gymnorhynchus for
we must look upon the inserted pedicle as the active animal.
In Csenurus, also, the pedicles are contained within the ex-
ternal membrane of the sac.
I shall finish these observations on the Cystic Entozoa,
with the following account by my brother John, of Neuronaia
Monroii* (Plate VI., Fig. V ; Plate XI., Figs. 2, 7.)
" The observations of Pacini J on the peculiar bodies which
are appended to the digital nerves, induced me to direct my
attention to the l spheroidal bodies/ described by the second
Monro, as existing on the surfaces of the brain and nerves of
the gadidae. I accordingly examined the ' spheroidal bodies '
in the haddock, and found that they were entozoa, referrible
to the family Distoma, and enclosed in cysts. I described
these curious parasites at a meeting of the Anatomical and
Pathological Society, and a short abstract was published
in the Monthly Journal of Medical Science. Till lately, I
had supposed that I was the first to observe the true nature
* Knox, Edinburgh Medical and Surgical Journal.
t Monro, Observations on the Structure and functions of the Nervous System
p. 59.
t Pacini, Nuovo Giornale dei Letterate, March and April 1836, p.
109. J. Henle and Kolliker, -Ueber die Padnischen Korperchen an den
Nerven des Menschen und der Sdugethiere.
496 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
of these 'spheroidal bodies,' when Dr. Allen Thomson
ascertained that Dr. Sharpey was in the habit of mentioning
them in his courses of lectures in the University College. I
accordingly wrote Dr. Sharpey on the subject, and I am
indebted to that gentleman for the following interesting
accounts of what has been already recorded regarding this
entozoon :
" When I was in Berlin some years ago, the late Professor
Kudolphi remarked to me in conversation, that he thought it
not unlikely the little bodies discovered by Dr. Monro 2d, on
the nerves of the cod, haddock, and other allied fish, would
turn out on examination to be entozoa ; and he suggested
that I should take an opportunity of inquiring into the point
on my return to Scotland. Accordingly, in the autumn of
1836, 1 examined these bodies in the haddock or whiting, I
really forget which, but I think it was the former, and found
that each of them was a little cyst, containing a Distoma,
which could be easily turned out from its enclosure alive.
The specimens I examined were from the membranes of the
brain.
" This observation was made in Edinburgh, and on going
to London soon after, I mentioned the fact to Mr. Owen ; and
I have been accustomed to take notice of it in my lectures
ever since, suggesting at the same time that it would be well
to search for them, or for analogous parasites, in the nerves
of other animals, as it was not likely that the gadus tribe of
fishes should be the only example. Indeed, unless my me-
mory deceives me, some one has met with something of the
same kind in the nerves of the frog ; and Valentin has seen
the eggs of Distoma in the vertebral canal of a foetal sheep.
When I learned that the oval bodies, which all must have
seen in the cellular tissue of the palm of the hand and fingers,
were connected with the nerves, I at first imagined they
THE CYSTIC ENTOZOA. 497
might be entozoa (having been led to make just the converse
of your conjecture), but Mr. Marshall, formerly of our mu-
seum, having examined these ' Pacinian ' bodies two or three
years ago (quite independently of any suggestion from me),
I found nothing to confirm this conjecture on his showing me
their structure. I have since seen Henle and Kolliker's me-
moir, which includes the substance of Pacini's observations.
" Kudolphi, as far as I know, never examined the structure
of the spheroidal bodies of Monro ; and the only notice of
them which I have met with in his writings (to which he did
not refer me) is in his Historia Naturalis Entozoarum, vol. ii.
part ii. page 277", when, under the head of ' Dubious Entozoa/
he enumerates an object described and figured by Kathke,
under the name of ' Hydatula Gadorum/ which that observer
found in the pia mater of the Gadus morrhua and 6r. virens,
often in great numbers, and which appeared to be a vesicle
containing a worm. The nature of the parasite was doubtful,
but supposed in some degree to resemble that of a Cysticercus,
and hence the name applied to it by Eathke, but Eudolphi
denies that it is a Cysticercus, though he does not know to
what genus to refer it, he adds * an Cucullanus?'"
This entozoon, as stated by Monro, is found in great num-
bers in the gelatinous substance which surrounds the brain,
spinal cord, and semicircular canals, in the cod, haddock, and
whiting. They are also very numerous in the larger branches
of the nerves, and particularly on those of the pectoral and
caudal fins. In the former situation they are suspended in
the gelatinous fluid by fibres of areolar texture and by blood-
vessels ; in the latter they lie embedded in the substance of
the nerve, the ultimate fibres of which are spread in bundles
over the surface of the cysts.
The cysts are produced spheroids, somewhat flattened;
their long axis measures about one-fourth of a line.
They consist of three tunics ; an external, which appears
2 K
498 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
to be derived from the areolar texture of the infested animal,
and of a middle or internal belonging to the parasite.
Upon the surface, and in the substance of the external
tunic, the bloodvessels of the nerve can occasionally be seen,
and recognised by their contents, One or two vessels may
thus be observed coasting along the cyst, accompanied by
single nerve-tubes, or by bundles of these, or by a mass which
completely incloses and conceals the cyst. The second tunic
is a fine transparent membrane, which lines the first, and has
in its turn its internal surface covered by an epithelial layer,
which is the third tunic of the cyst. The epithelia are flat,
irregular in shape, and somewhat opaque. The third, or in-
ternal layer, formed by them, breaks up under the pressure of
the glass plates, so as to present rents or fissures passing in
various directions over it.
The cyst, in addition to the worm, contains a small
quantity of fluid, in which oil-like globules of various sizes
float.
The worm is a Distoma, oblong, dilated in front, tapering
slightly towards its posterior extremity. The mouth, longi-
tudinally oval, and rather pointed posteriorly, is surrounded
by the usual suctorial disc. The acetabulum is situated at
the junction of the anterior and middle third of the animal,
and can be protruded from the surface of the body.
On the anterior edge of the acetabulum a minute pore is
situated, and communicates with a sac, to be afterwards
described.
At the posterior extremity of the animal another orifice is
placed, which forms the outlet of the large chyle-sac, and
apparently also of another sac, to be afterwards alluded to.
The integument of the two anterior thirds of the body is
closely covered with short slightly-curved spines, directed
backwards. These spines are largest round the suctorial
mouth, and on the posterior part of the body are gradually
THE CYSTIC ENTOZOA. 49 ( J
replaced by minute tubercles or dots. Under this spiny or
euticular layer, the integument is muscular, the fibres being
principally transverse, and so arranged that the animal appears
to be made up of a series of rings, as may be observed along
its edges, when examined by transmitted light.
From the anterior extremity to the acetabulum the integu-
ments are so opaque, from the dense covering of spines, that
the internal structure of the animal cannot be detected. It is
probable, however, that the oesophagus terminates, as in the
family Distoma generally, in two blind intestinal tubes. I
have failed in detecting an arrangement of this kind ; but I
have observed about the middle of the animal, and along the
sides of its posterior half, a sort of cellular structure, which
may, probably, belong to the digestive system, as in Distoma
clavatum described by Professor Owen.*
A large sac, evidently connected with the digestive system,
opens externally by the minute orifice at the posterior part of
the animal. This sac, in every individual, is full of a matter,
which, by reflected light, is of a chalky whiteness, and de-
scribed by Monro, and conjectured by him to be of a cretaceous
nature. Examined by transmitted light, it is seen to consist
of numerous spherical globules of variable size, and resembling
the matter which fills the chyle-cells of the intestinal villi.
The larger sac in which this matter is contained varies ^in
shape, but it generally passes up from its outlet for about a
third of the length of the body of the animal, then takes an
acute bend to the other side, and passing forwards in a curved
direction, ends in a dilated blind extremity between the
acetabulum and the mouth. It is the " sigmoidal " or " ser-
pentine body " of Monro. This sac is evidently the " cisterna
chyli."
It does not communicate directly with the digestive
* Owen, "On the Anatomy of Distoma clavatum:" Trans. Boy. Soc.
vol. i.
500 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
system, as in the apparently analogous receptacles in Distoma
clavatum, nor, as far as I could see, with the vascular system ;
but I have seen it discharge its contents by the posterior
orifice, in the manner described by Nordman in Diplostomum
volvens*
From the movements of the walls of this receptacle, or
from contractions of the animal itself, an active motion of the
particles of its contents is occasionally observed. The move-
ments occasionally resemble very much those produced by
cilia. This sac is apparently a secreting organ, and is pro-
bably the only arrangement by which feculent matter is re-
moved from the body of the animal. The food of an animal,
living as this does in a cyst, is already digested by the walls
of its cyst. Its food, therefore, yields no mechanical feculent
matter, and its intestinal tube requires no anus. The only
outlet which such an animal requires is for chemical feculent
matter, which in all animals is the product of secretion, and
principally of the lung, gill, or kidney. This sac, may, there-
fore, be considered as a respiratory organ or kidney.
There is another sac, very uniform in shape and size,
situated at the posterior part of the body. This sac is
elongated, extending from near the outlet of the "cisterna
chyli," forward about a fourth of the length of the animal.
Its posterior extremity is funnel-shaped, and appears to me,
although I have failed in tracing it distinctly, to open
externally along with the "cisterna chyli." It appears to
possess circular fibres, which constrict it slightly at regular
distances. The three anterior fourths of its wall are so thick
that the cavity appears linear. This thick part of the wall
exhibits an arrangement of fibres or particles perpendicular
to its surface. The thick portion terminates by forming a
curved projection into the thin posterior part of the organ,
the whole arrangement resembling the projection of the
* Nordman, Microyraphisclie Beitrage, p. 38, lift. 1.
THE CYSTIC ENTOZOA. 501
human os uteri into the vagina. This organ, in its relations
and structure, appears to be the analogue of the cavity
described by Professor Owen, as opening into the posterior
orifice of Distoma clavatum, and supposed by him to be a
respiratory organ.
A pyriform sac, communicating with the exterior by the
pore in front of the acetabulum, and two large, with occa-
sionally two smaller globular masses, would appear to be the
analogues of the reproductive organs. The pyriform sac
always contains highly refractive oil-like globules, but larger
than those in the chyle-receptacle. The two larger globular
masses are very constant, and, as well as the two smaller,
contain a mass of particles apparently nucleated. From the
two larger, I have only been able to see faint traces of what
appeared to be ducts passing in the direction of the smaller
masses, and towards the neck of the pyriform sac. Whether
these convoluted bodies be ovaries or convoluted oviducts,
and the pyriform sac a uterus ; or whether the former be
the testes, and the latter the female organ, as in the arrange-
ment described in the other Distomas ; or whether they be
reproductive organs at all, I have failed in satisfying myself,
in consequence of the delicacy of their texture, and the com-
paratively dense integument of this part of the animal.
This Distoma possesses a vascular system forming a net-
work throughout the body. The two principal trunks, as in
the other genera, passing along the sides of the body and
being most apparent at its posterior third.
I. ACEPHALOCYSTIS.
Completely buried in the textures of the infested animal
young only consisting of three membranes; adult of four, the
external one belonging originally to the infested being.
Nourished by epithelial cells, which are contained in one of the
502 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS.
membranes composing the sac. Generated by means of cells
arising from a germinal membrane. Internal cavity filled with
a watery fluid.
1. Acephalocystis simplex (Mihi).
Parent sac quite transparent, with the membranes indivisible and the
germinal cells very minute.
2. Acephalocystis monroii (Mihi).
Parent sac transparent and gelatinous ; germinal membrane intersected by
membranous bands, which form flattened compartments, in which are large
cells containing unequal numbers of young cells. Each of the young is
marked with one or more dark spots.
3. Acephalocystis armatus (Mihi}.
Parent sac opaque, membranes distinct, germinal membrane composed of
a soft granular matter, in which the germs are arranged irregularly ; they are
globular and armed with an irregular circlet of teeth at the part opposite that
of attachment.
II. ASTOMA (MIHl).
Not buried, but attached by means of a pedicle, which
becomes very slender as the animal increases in size. Young,
globular and corrugated ; adult, botryoidal and smooth ; epithe-
lial cells ; with some appearance of tubuli in external coat.
Young remain and increase in size within the membranes of the
parent, till she bursts, when they become attached to the
peritoneum.
4. Astoma accphalocystis (Mihi}.
Botryoidal, that part of the interior not occupied with the young filled
with a yellowish gelatinous matter.
III. DISKOSTOMA (MIHl).
Peduncular. Whole group covered by a disk bearing
tubular membrane.
5. DisTcostoma accphalocystis (Mihi).
Globular interior filled with gelatinous matter, of a transparent greenish
ellow colour.
THE CYSTIC ENTOZOA. 503
iv. SPHAIRIDION (MIHI.)
S. Animal enclosed within a cyst which is composed of two
membranes. Sac single, containing the pedicle or reproductive
body in its centre, and presenting a number of concentric
coloured rings. Hob. Peritoneum of Crested Balearic Crane.
V. C^NURUS RUDOLPHI.
Sac double, armed with numerous clusters of toothed
pedicles. Epithelial cells in the sac. Germinal cells in the
pedicles. Buried.
6. Ccenurus liepaticus (Mih'i).
Sac botryoidal, opaque and thick ; pedicles internal, small, suckers
obsolete ; teeth barbless, small, irregularly bent, and forming one irregular
series. Gregarious. Infests the liver of man.
7. 0. cerebralis (Rudolphfy.
Sac globular, transparent, thin, pedicles with four or five acetabula.
Teeth thirteen, about three times as long as the breadth of the disc from
which they arise. Infests the brain of sheep and other ruminants.
VI. CYSTICERCUS.
Animal enclosed within a cyst provided with a single pedicle.
1. Cyst formed from the infested animal.
8. 0. neglectus (Miln).
Cyst formed from omentum of infested animal. Pedicle about three times
the length of sac, head rounded, teeth twenty-one in number, very long,
slender, and bent at the extremity, barbed on bent edge. Hob. unknown.
2. Cyst formed by parasite, as well as from textures of
nfested being.
9. 0. rattus (Mihi).
Cyst small, globular, and transparent pedicle, not very long, teeth short,
sickle-shaped, being curved throughout their whole length.
VII. ECHINOCOCCUS.
H. D. S. G.
504 DESCRIPTION OF AN ERECTILE TUMOUR.
XXXIV. DESCRIPTION OF AN EEECTILE TUMOUR*
THIS tumour occurred in the foot of an infant five months
old, which was amputated by Mr. Syme. A fine injection of
size and vermilion having been thrown into the arteries of the
foot, the skin assumed a red tint, except where it was so
attenuated as to display the peculiar bluish colour of the
subjacent diseased mass.
It was then cut longitudinally into two portions, A gush
of venous blood reduced its size very considerably. By means
of a gentle stream of water, the rest of the contained blood
was washed out, all pressure being avoided.
The two halves were then laid in a basin of spirit, and by
means of a syringe that fluid was forced into the diseased
mass, so as to distend the whole almost to its original size.
After having been hardened, fresh longitudinal sections
were made, avoiding all pressure, and the structure was
examined.
The venae saphense, plantar, and posterior tibial veins were
much enlarged, and had undergone a peculiar change, which
consisted of increased bulk of the fibrous fasciculi of their
coats, and of longitudinal and oblique foldings of the parietes,
due partly to the fasciculation partly to actual involution.
About the centre of the foot the veins broke up into the
general cellular arrangements which constituted the disease,
the saphense forming a sort of central cavity on the dorsum,
the plantar a much larger cavity or central areola in the sole
of the foot.
The diseased mass itself consisted of areolse, which de-
* Cormack's Monthly Medical Journal, 1845, p. 342.
DESCRIPTION OF AN ERECTILE TUMOUR. 505
creased in size from the central venous cavities to the surface
of the skin, and to the deep limits of the disease, these limits
being denned by the internal membrane of the venous system,
which was continuous through all the areolae.
The diseased mass had not displaced the surrounding tex-
tures, but had caused them to disappear before it, as in certain
malignant growths and ulcerations bone, ligament, muscle,
and fat having equally failed in resisting its progress, the skin
alone standing out against its advance, and along with the
venous membrane forming the limit of its superficial position.
The areolae of which the mass consisted were elongated
from the central cavities towards the limits of the disease,
being more elongated the nearer they were to the centres.
The peculiar form of the areolae was due to the radiated direc-
tion of the bars and imperfect laminae which separated them,
these being thicker, stronger, more elongated, and more sepa-
rated from one another around the central cavities than near
the circumference, where they were shorter, firmer, and much
more numerous.
The bars and imperfect laminae consisted of fibrous tex-
tures exactly resembling that of the tendinous ligaments, and
aponeuroses with numerous germinal centres.
The bars and laminae were all covered, and consequently
they contained areolae, lined by a fine membrane, consisting of
tesselated epithelium, and continuous with the lining mem-
brane of the venous system, at the central cavities or diseased
terminations of the saphenae and plantar veins.
In many of the bars and laminae small arteries were
situated, and one of these was traced nearly to the termination
of the anterior tibial on the back of the foot, It was not
ascertained how the arteries terminated, but it was presumed
that they passed by small oblique orifices into the venous
areolae, as the curling arteries of the human placenta pass into
the venous areolae of the decidua.
506 DESCRIPTION OF
XXXV. DESCRIPTION OF A CONGENITAL TUMOUR
OF THE TESTIS *
THIS tumour was removed by Dr. James Duncan from a boy
eight years old. When the tunica vaginalis was cut into, a
considerable quantity of matter mixed with hairs was evacu-
ated. The tumour possessed the following characters : A
mass of an irregular ovoidal form, about the size of the last
joint of the forefinger, appeared to be the testis, so much
altered in texture as to present no trace of its original
structure.
It consisted almost entirely of fibrous texture, inclosing
fat-cells in its areolae, and, at variable distances throughout,
small tubercular masses of a light yellow tough substance, of
a granular aspect, resembling some forms of scrofulous deposit.
Near the reflection of the tunica vaginalis, on the surface
of the testis, two club-shaped projections were attached,
covered by a layer of a substance resembling the ordinary
integument, with a quantity of fatty cuticular debris upon it.
This portion of integument somewhat suddenly became con-
tinuous with the surface of the tunica vaginalis.
On the surface of the club-shaped projections, and at the
angle of reflection of the tunica vaginalis, numerous long hairs
were attached by bulbs. These hairs, of one-half to three-
fourths of an inch in length, were conical, pointed, and of two
kinds, some having their conical pulp-cavities prolonged in the
form of canals, full of cells to their extremities ; others were,
with the exception of their conical pulp-cavities, solid.
The integumentary membrane in which the hairs were
* Northern Journal of Medicine, June 1845.
A CONGENITAL TUMOUR OF THE TESTIS. 507
implanted, resembled in all respects the ordinary skin of the
surface of the body.
A few hairs appeared to arise from the general surface of
the tunica vaginalis.
In the substance of the club-shaped projections, but par-
ticularly in the larger of the two, where it adhered to the
mass of the testis, there were irregular masses of soft cartilage,
presenting all the ordinary characters of the corpuscles of
that texture, and a few vascular canals.
In some places this cartilage had been converted into bone,
in which were visible irregular Haversian canals and numerous
corpuscles and canaliculi.
One portion of bone resembling a sand-glass measured
half-an-inch in length.
598 THE CURVATURES OF THE ARTICULAR SURFACES, ETC.
XXXVI. ON THE CUEVATUEES OF THE AETI-
CULAE SUEFACES, AND ON THE GENEEAL
MECHANISM OF THE HUMAN HIP-JOINT*
IN consequence of the vague and unsatisfactory manner in
which anatomists and physiologists have until lately exam-
ined the mechanism of the joints, it appears to have been
assumed as self-evident that the cartilaginous surfaces of the
head of the thigh-bone and of its socket must be spherical.
If, however, the outlines of the transverse and antero-posterior
curvatures of the head of the femur be attentively followed
by the eye against the light, it will be at once observed that
they are not arcs of circles. The transverse curves as seen from
the front or back of the bone are two in number, one above,
the other below the fossa for the ligamentum teres, and they
increase in rapidity as they approach that fossa.
The transverse curves are also two in number, and may be
observed by looking at the outline of the head of the bone
from the inner side, holding it so that the ridge extending
from it to the lesser trochanter may be perpendicular. If the
line of the ridge be then traced upwards to the outline of the
articular surface of the head of the bone, it will be found to
intersect that outline at the point of osculation of the two
curves of which it consists. This point is a cusp directed
upwards, and the two curves increase in rapidity as they
extend down to the front and back of the articular margiu.
On examining the articular surface, the eye will now be able
* This memoir ought to have immediately followed that on the Mechanism
of the Knee-joint, but the manuscript from which we print was unfortunately
overlooked until the greater part of this volume had gone to press. EDS.
THE CURVATURES OF THE ARTICULAR SURFACES, ETC. 509
to trace this cusp to a ridge extending across from the neck
of the bone to the fossa, dividing the surface into an anterior
and posterior area. If the eye be carried along two series of
lines diverging from the upper angles of the fossa, the one
series outwards and forwards on the anterior area, and the
other outwards and backwards on the posterior area, and with
a convexity on each line towards the ridge corresponding to
the curvature of that part of the surface on which it is traced,
each series will be found to close with the anterior and
posterior margins of the fossa for the ligamentum teres. It
will also be observed why the transverse lines of curvature
increase in rapidity from above downwards.
The cartilaginous surface of the acetabulum consists of
three areas situated respectively on the pubic, iliac, and
ischial portions of the cavity. They are more or less dis-
tinctly separated in the dry or recent bone by depressed lines.
The marginal terminations of these lines are indicated at the
brirn of the cavity by the three notch-like hollows of the edge,
that between the ischial and iliac at the middle of the
posterior margin ; that between the iliac and the pubic on
the upper margin at the outer side of the ilio-pectineal
eminence ; that between the pubic and ischial by the fossa
and notch of the lower part and margin of the cavity. These
three notches, with the three intermediate wave-like projec-
tions, produce an undulating form of margin in the macerated
bone. The three projections are respectively formed by the
upper part of the iliac, the lower part of the ischial, and the
anterior part of the pubic portion. The margin of the arti-
cular surface on the head of the femur is also undulating.
It sweeps outwards opposite the front and back of the great
trochanter, and slightly below opposite the lesser trochanter,
and therefore recedes inwards opposite the upper margin of
the great trochanter, also before and behind the ridge which
connects the head to the small trochanter. In the erect
510 THE CUKVATUKES OF THE ARTICULAR SURFACES, AND
position, that is when standing on both feet, the hip-joint
being in full extension, the posterior area of the head of the
femur is in close contact and congruent with the ischial area
of the acetabulum, the undulation outwards of the posterior
margin of the articular surface of the head of the femur
occupying the broadest part of the ischial surface of the
acetabulum ; while the undulation inwards of its upper part
occupies the notch in the margin of the acetabulum, between
the ischial and iliac portions of the cavity.
In semi-flexion of the hip-joint, the anterior area of the
head of the femur is congruent with the iliac area, this
broadest or projecting portion occupying the undulation of
the former, which extends outwards on the front of the neck
of the bone ; while the inward undulations on each side of it
occupy respectively the acetabular notches between the
ischial and iliac v and bqtween the iliac and pubic portions
of the cavity.
The anterior border of the femoral pit is the thread of this
screwed area, and curves more rapidly as it approaches the
posterior angle of the attachment of the lig-teres. The area
itself is the rolling surface. It is a right-handed screw in the
right hip, a left in the left. It therefore screws the head of
the thigh bone out of the socket in flexion, but screws it
against the iliac area, advancing its superior external angle or
apex against the outer or projecting marginal portion of that
area. During the action of this area the ilio-femoral ligament
is slack ; when completed the pubic and ischial portions of the
capsule become tense and act as the tightening arrangements
of the combination.
In complete flexion the lower portion of the posterior
area of the head of the femur, which occupies the cotyloid
fossa during semi-flexion, is applied and rests upon the pubic
area ; the posterior undulation outwards on the femur which
occupies the ischial projection in full extension, now occupies
THE GENERAL MECHANISM OF THE HUMAN HIP-JOINT. 511
the pubic projection, and the pubic notch is occupied by the
posterior inferior inward undulation.
In complete extension, as in standing erect on both feet,
the posterior area of the head of the femur is congruent with
the ischial area of the acetabulum, and with the superior
internal portion of the iliac area ; being screwed backwards,
upwards, inwards, and forwards, by the action of the extensor
muscles of the hip, and by the tightening of the successive
fasciculi of, and ultimate tension of, the entire ilio-femoral
portion of the capsule. During extension, the thigh passes
backwards and outwards, rotating outwards at the same time.
It is, to use the current nomenclature, a combination of ex-
tension, abduction, and rotation outwards. These movements
are the necessary accompaniments of the movements already
described between the posterior femoral, and ischial articular
areas. The movements of these two areas in extension are
such that the male or femoral area advances by a combination
of rolling and gliding along the female or ischial, apex towards
apex, and base towards base, until the opposite convex and
concave surfaces become congruent throughout, and the joint
is screwed home in extension. If a portion of the inner wall
of the acetabulum be removed, so as to display the respective
movements of the areas under consideration, the most pro-
minent portion of the femoral area will be observed to
advance inwards and forwards, as it advances laterally along
its action of rotation. The head of the femur is thus, during
extension, screwed, and therefore forced into the acetabulum ;
from without inwards, and from behind forwards. The
posterior border of the femoral pit constitutes the proper
thread of this screwed area ; its superior more rapidly curved
portions at the posterior extremity of the attachment of the
lig.-teres advancing during the movement forward and inward.
The area itself constitutes the rolling surface. This area, with
the ischial and deeper portion of the iliac, constitutes a right-
512 THE CURVATURES OF THE ARTICULAR SURFACES, AND
handed screw combination in the right, a left-handed in the
left hip.
The ligamentum teres. When the posterior area is
screwed home, the round ligament is quite slack and folded
over on itself forwards ; the posterior angle of its femoral
attachment having revolved over and in front of its anterior,
while the posteriqr area is screwing off, that is, performing the
first half of flexion, by screwing and rolling backwards, down-
wards, and onwards, the ligamentum teres gradually tightens,
so that when the shaft of the thigh bone has passed so far
forwards and inwards as it is when the foot comes in contact
with the ground in the step, when the trunk has inclined
slightly forward to the same side over the head of the thigh
bone, it becomes quite tight, flattened out, and lodged in the
cartilaginous fossa below the femoral pit, and bounded on each
side by the screwed anterior and posterior borders of that
groove. The joint is now in mid flexion (or mid extension),
that is, the posterior femoral area, and the corresponding
cotyloid area are about to break contact, and the anterior
femoral and corresponding area to come into action. When
this takes place the ligamentum teres again gradually
slackens, folding backwards with its anterior angle of femoral
attachment revolving over the posterior. In extreme flexion
when the lower part of the posterior area of the head of the
femur passes across the non-cartilaginous fossa of the acetabu-
lum and rests on the pubic area, a position which can only be
assumed along with extreme abduction, the ligamentum teres
folds still further backwards and inwards. As the hip joint
is essentially a hinge joint, the ligamentum teres represents
the internal lateral ligament, as the capsular is a modified
external lateral ligament. The fossa for the femoral
attachment of the ligamentum teres lies in the line of oscu-
lation of its two areas ; and, therefore, like the internal lateral
ligament of the hock-joint in the horse, becomes tense at mid
THE GENERAL MECHANISM OF THE HUMAN HIP-JOINT. 513
action. The anterior and posterior bands of this ligament are
reciprocally related to the anterior and posterior areas of the
femoral head, and of the acetabulum, as the ilio-femoral and
pubo-ischial femoral are.
On the Movements of the Hip-Joint. The movements of
the elbow and ankle-joints take place in an anterior and a
posterior conical screw combination in each joint. These com-
binations are both dexiotrope or both scoeotrope in each joint,
according to the side to which the joint belongs. The axes
of the fundamental cones lie more or less obliquely across the
joint, one in front of the other the apices of the cones
pointing, the one outwards, the other inwards. The so-called
movements of flexion and extension in these joints that is,
presumed movements in the same antero-posterior plane are,
in fact, movements of flexion and extension produced by
combined gliding and rolling along one conical helicoid course
in the anterior half, and along a second in a reverse direction
in the posterior half of the articular path. As, however, the
axes of rotation of both screw combinations are so nearly
coincident with the axes of the presumed hinge movement,
the actual variation from such a movement is not at first
obvious. For the same reasons the movements are princi-
pally screwing or gliding, with a minimum of rolling ; the
gaping, therefore, is comparatively slight. It is evident that
the path described by a point in either of the segments of the
limb, between which the joint is placed, must be a double
helix that is, two conical helices, corresponding respectively
to the anterior and posterior screw combinations of the joint
oscultating with one another. It must also be evident from
the double-threaded form of the screwed surfaces of these
joints, and the peculiar configuration of their opposite arti-
cular surfaces, that they do not admit of the movements
technically termed adduction, abduction, and rotation.
The anterior and posterior screw combinations of the knee-
2 L
514 THE CURVATURES OF THE ARTICULAR SURFACES, ETC.
joint differ from those in the elbow and ankle in their axes
being nearly perpendicular to the horizontal plane of the
joint, that of the anterior being directed with its vertex
upwards and slightly backwards and outwards ; that of the
posterior upwards and slightly forwards and inwards. The
shallow transverse curvatures of the rolling areas of the male
elements, and the wavy convex form of the corresponding
curvatures of the female elements, would appear to render
lateral and circumductory movements of the knee-joint
possible. It will be found, however, that throughout the
whole extent of its double helicoid movements, it only permits
of eversion and inversion of the toes at the stage beyond semi-
flexion ; these movements, due to the action of the biceps and
semi-membranous being again excluded when the joint is
flexed home.
The hip-joint, from the ball and socket form assumed, by
its combined anterior and posterior screw combinations, is not
only capable of pursuing its fundamental double helicoid
path, but also of performing the so-called adduction, abduc-
tion, and circumduction movements in all parts of its course,
but more particularly towards the close of flexion.
INDEX TO VOL. II.
ABSORPTION, nature of, 397 ; and ulcer-
ation, and the structures engaged in
these processes, 403-407
Acephalocyst or simple hydatid, 476-482 ;
Acephalocystis armatus, 478, 502 ;
A. simplex, 480, 502; A. monwii,
482, 502
Acetic acid in fluid which contained Sar-
cina ventriculi, 370
Acids found in stomachs of animals, 368,
369
Acting facets of articular sxirfaces, their
curvatures and movements, 246-264
Alpidium ficus, hepatic organ of, 415
Amaryllis, electric current at time of
flowering, 315
Anatomical and pathological observa-
tions, 387-503
Anatomy, the study of, to be advanced
by ascertaining the accurate shape,
form, and proportion, geometrically,
209
Anemone, electric descending current at
time of flowering, 315
Annulosa, eye how acted on, 280
Annulose type of organisation, on mor-
phological relations of nervous system
in, 78-87
Anomoura (Crustacea), organs of genera-
tion in, 430
" Antaxial couple," meaning of, 258
Aphotogenic rays, 278
Aplysia punctata, liver of, 415 ; secre-
tion from mantle, 416, 425
Apple and pear, electrical current in
fruit of, 315
Apteryx, nasal fossae, arrangement of,
153
Arm in well-made man straight, 218
Arnold, paper in Salzburg Journal, 1831,
referred to, 11, etc. ; on formation of
milk-tooth sacs, 51, 52
Articular cartilages, the process of ulcer-
ation in, 408-411 ; couple, what Pro-
fessor Goodsir means by the term,
247 ; surfaces, memoir on the curva-
tures and movements of the acting
facets of, 246-264 ; on the curvatures
of the, 508-514
Artist, how he might draw better pro-
portioned figures, 214-218
Astoma acephalocystis, 482, 502
" Axial" couple," meaning of, 258
Azalea, electric current at time of flower-
ing, 315
BAER (Von) on morphological character
of supra- oesophageal ganglion, 86, 87
Bacillary layer of the retina, 265 ;
Gottsche and Hannover on, 268 ; its
morphological relations, 271
Balearica pavonia, entozoon in, 487
Balce-na mysticetus, tooth-germs in foetus
of, 54
Barry (Dr. Martin), paper on the cor-
puscles of the blood referred to, 389 ;
development of cells from parent
centre, 391
Basement membrane of Bowman, 391
Batteries in Gymnotus, 291, 292 ; in
Malapterurus, 293, 294 ; of the fish
independent electromotor structures,
341, 342
Battery in electrical fishes, 289, 299,
304, 305
Baxter on electrical currents during
secretion and respiration, 300 ; on the
electric relations of mucous membrane,
320, 322 ; of gland, 321
Beauty of proportion in human body,
Hay on, 215
Becquerel on electricity in vegetables,
referred to, 308, 318
Bell, Anatomy of Teeth referred to, 33,
35 ; note in Palmer's edition of
Hunter's works quoted, 21
Berzelius on difficulty of distilling viscid
animal fluids in retorts (note), 362
Bilharz (Dr.), on the electric organ in
Nilotic MalapteniruSj'294
Biology, how its study has been pro-
moted, 205, 206
516
INDEX.
Birds, centrum of pre-sphenoidal sclero-
tome in, 149-154 ; from size of organs
of vision, have great development of
principal frontal, 156
Birth, state of teeth at, 23
Blake, Structure and Formation of Teeth
referred to, 21, 33
Blastema announcing formation of a
gland in embryo, 425
Blastoderma, the first form after com-
mencement of development, 73
Elennius vivipams, Rathke on cartilagi-
nous streaks at the basis of head in
embryo, 186
Blumenbach on the enclosure of bullets
in ivory, 58
Bone : how dead or dying bone is sepa-
rated from the living structure, 406 ;
the structure and economy of, 461-464
" Bones of Bertin," 158, 163
Bowman, paper on muscle referred to,
389 ; fat deposited in liver, 382, 413 ;
on basement membrane, 391 ; paper
on the structure and use of the Mal-
pighian bodies of the kidney referred
to, 391, 428 ; on mucous membrane,
396, 428
Brachyura (Crustacea), organs of gener-
ation in, 430, 435
Brain in Crustacea, its position, 80 ; in
insects, annelids, and mollusca, 81
Bremser, Intestinal Worms of Man,
quoted, 481
Bright, figures of ulceration of Peyer's
patches, 378
Brisbane (Lady), sends gold-fish with
parasitic conferva on it to Mr. Bryson,
345
Briicke and Hannover on the rods and
cones of bacillary layer of retina re-
flecting light back, 269
Bryson (Alex.), on vegetable nature of
growth on fin and tail of gold-fish, 345
Euccinum undatum, liver of, 415
Bulbs, tooth-pulp and its sac, 51
Burdach's Physiologic referred to, 20
Bursarice on filaments of conferva of
gold-fish, 350
Cccnurus cerebralis, 487, 503 ; C. hepa-
ticus, 489, 503
Camels, canine teeth in, 53
Camper on metallic bodies inclosed in
ivory, 58
Canine and upper incisors, germs of, in
embryo of cow and sheep, 53
Carabus catenulatus, hepatic caeca of, 41 5
Carcinus mcenas, hepatic caeca of, 415 ;
liver of, 423
Carp, interorbitul space in, 157
Carswell on cirrhosis of liver, 382
Cartilage, nature of, 408
Cams, view of the morphology of nervous
system in annulosa, 79; division of
skeleton, 102
Cassowary, olfactory chambers of, 153
Catacentric sclerotome, 110
Catametopa have large generative organs,
429
Cell (central), origin of others, 390
Cells, various kinds of, in animals and
vegetables, 403
Cell-wall does not separate and prepare
secretion, 426
Cement of elephant's tusk, exogenous
growth of, 59
Centres of nutrition, 389-392
Centrifugal and centripetal nerves, their
electric relations are identical, 337
Cetacea, substance in pulp-cavities of
teeth, 62
Changes in pulps and sacs at various
stages till the eruption of the wisdom-
teeth, 26-43
Chemical action, cause of electricity in
vegetables, 318
Chemistry, mechanics, and other physical
sciences, how the knowledge of them
was advanced, 206, 208
Child at birth, development of pulps and
sacs of teeth in, 23 ; between four and
five years old, sac and pulp of teeth
in, 25, 26 ; six years old, 26
Chyle, absorption of, in fresh subjects,
394
Cirrhosis of liver, 382
Claudius on Corti's membrane, 283-286
Cochlea, on the lamina spiralis of, 282-
288 ; Dr. Young's opinion that it was
a " micrometer of sound," 287
Cod, interorbital space in, 156
Comb on a spear-head found in tusk of
elephant, 64
Cones of retina, 265 ; seat of impression
of light, 209 ; Goodsir's opinion that
they are not nervous structures, 270
Confervce, their mode of reproduction,
212 ; which vegetate on the skin of
the gold-fish, 345-350
Contraction (muscular) electric condition
during, 328
Cooper (Sir Astley) on structure of
thymus, correction of one of his ob-
servations, 74 ; (Daniel), cotton-like
conferva on gills and fins of gold-fish,
350
Corti, membrane of, in cochlea, 283
Cow, follicular stage of dentition in, 53
INDEX.
517
Crab, how it acts on the injuring of a
limb, 471
Cranium of mammal, how it differs from
that of the other vertebrata, 114
Crocodiles, observations made by Good-
sir in dissection of, 98, 99 ; peculiar
position of their nostrils, 118, 119
Cruikshank (William), Anatomy of the
Absorbing Vessels of the Human
Body, referred to, 393, 443
Crustacea, Geoffrey St. Hilaire's opinion
of their relations, 79 ; brain in, its
position, 80 ; development of seminal
secretion in, 427 ; on the mode of re-
production of lost parts in, 471-475
Crystalline column, 278 ; of compound
eye, 279
Cuvier, on the bone and ivory around
bullets in tusks of elephant, 59 ; " os
en forme de cuiller" in lizard, what,
151
Cyclometopa, the most prolific Crustacea,
429
Cyclostomous fishes, nasal passage of,
173-175
Cyprinoid fish, post-stomal sclerotome,
176
Cystic entozoa, anatomy and develop-
ment of, 476-503
Cysticercus cellulosus, 490 ; C. rattus,
491 ; C. neglectus, 503 ; species of,
found in almost every part of human
body, 493
DALRTMPLE on the structure of human
placenta, referred to, 446-449
Davy (Dr. ), on the torpedo, 344
Dexiotrope movements, 260
Diacentric sclerotome, 111
Diaphragms (electric) in torpedo, 290,
291 ; in gymnotus, 292, 293
Diatomacece, their mode of reproduction,
212
Dicotyledonous plants, electrical currents
in, 310, 311
Digestion, functions of, 400, 401
Diplostomum volvens, Nordman, 500
Discs of mass on each side of tail of
skate, their structure, 295
Diseased structure in one animal iden-
tical with normal structure in another,
62, 63
Diskostoma acephalocystis, 483-502
" Distal" margin in movements of joints,
248
Distoma clavatum, Owen, 499
Dodo, Dinornis, and other extinct birds,
structure of bones of head, 152, 153
Donne, opposite electrical conditions of
different parts of vegetables, 308 ; on
electric phenomena of membrane and
gland, 319-321
EAR, structure of parts of, 282-288
Echinococcus hominis, 480 ; E. veterin-
orum, 481
Echiurus vulgaris, caeca of, 416
Ecker, communication on Bilharz's ana-
tomy of electric Nile fish, 294, 299
Edentulous mammals likely to have
germs of teeth in foetal state, 54
" Edinburgh Dissector," referred to, 35.
Electric organ, various opinions on its
action, 338-341 ; fishes do not feel
electric discharges produced by them-
selves or other individuals of the same
species, 343
Electrical apparatus in torpedo, gymno-
tus, and other fishes, 289 ; disturb-
ances in the processes of living organ-
ised bodies, as noticed by Galvani,
Matteucci, and Du Bois Reymond, 299
Electricity (organic), a brief review of
the present state of, 306-350 ; pecu-
liar character of that evolved from the
batteries of the fish, 342
Electrotonic state of nerve, 333-335
Elephant, successive dentitions conducted
in a cavity of reserve, 41 ; on bullets
and other bodies inclosed hi the tusks
of, 56-65.
Embryo of sixth week, dental arches in,
1 ; seventh week, 4 ; second month,
6 ; nine weeks old, 8 ; tenth week,
9; llth or 12th week, 10; 13th
week, 11 ; 14th week, 12 ; 15th week,
14 ; 16th week, 16 ; fifth month, 18 ;
forms must be studied in morpho-
logical inquiries, 83
Enamel pulp of Hunter, 33 ; deposition
of, 54
Endogenous growth of ivory, 59
Entomosome, a segmented animal, 84
Entozoa (cystic), Harry Goodsir on their
anatomy and development, 476-503
Equiangular spiral, its characteristic
property, 253
Eruptive stage of dentition, 44
Erdl, dissertation on Helix algira, 413
Ethmoidal sclerotome, 122-148; remark-
able modification of, in the bird, 127-
130 ; in the chelonian, 130 ; in the
crocodiles, 131 ; in lacertians, 136 ;
in ophidians, 137 ; in amphibians,
138 ; views hitherto taken of it, 139-
143
Exogenous growth of cement of elephant's
tusk, 59
518
INDEX.
External lamella of Blake, 33
Eye : on the raode in which light acts on
the ultimate nervous structures of the
eye, and on the relations between sim
pie and compound eyes, 273-281
FACETS of patellar surface, peculiarity of,
234
Faraday on the power of gymnotus to
strike fish motionless, 304 ; his re
searches on electricity, 306 ; on the
atmosphere of power around fish at
the time when electric organs are dis-
charged, 343
Figures, Mr. D. E. Hay shows how they
might be drawn in good proportion,
214-219
Filamentary layer of the retina, 267
Fin-rays of fishes, 105
Final causes, the study of, furthering the
progress of biology, 206
Fishes, bony rays of, 104 ; composition
of head, 113 ; from size of organs of
vision have great development of prin-
cipal frontal, 156
Flower, electrical condition of, 314
Follicular stage of dentition, 44 ; in
ruminants, etc., 53-55
Food, changes of, in gut, of a chemical
nature, 400
Formation and growth of ivory, 60
Fox, Natural History of the Human Teeth,
referred to, 33
Frog, Galvani's observations on electrical
contractions in the muscles of, 322 ;
Nobili on electric current in nerve
and muscles of, 323, 328, 330, 334 ;
palatals in 161-163
Fruit, Donne's observations on electrical
condition of, 315
GALATHEA, testis in, 431, 434
Galvani on animal electricity, 319, 322
Gelatinous body between pulp and sac
of teeth, 20
Generation of Sarcina, 358 ; (organs of)
in male crustacean, 429
Geoffrey St. Hilaire detects tooth-germs
in foetus of whale, 54
Geometrical formation of shells shown
by Professor Moseley, 209-211 ; cha-
racter of the configuration and move-
ment of central articular facets, 247-264
Germinal membrane, 391-392, 400;
spot of the ovum, centre of nutrition,
389
Germination of plant, electrical rela-
tions of plant to soil and air reversed |
after, 310
Germs of the teeth, 43 ; of canine and
upper incisors in embryo of cow and
sheep, 53
Giraffe, antlers of, 149
Gland, electric relations of, 321
Goethe on the elements of three distinct
cranial segments, 197
"Go-lines" of ankle-joint, 237
Gold ball found at Amsterdam in ele-
phant's tusk, 57
Gold-fish, on the confei-va vegetating on
the skin of, 345-350
Gonidium, a genus of Ehrenberg's, 360
Gonium, how its square form is pro-
duced, 211 ; characters of the genus,
359 ; G. hyalinum, glaucum, pectorale,
punctatum, tranquilhim, 360
Goodsir (Harry), paper on the develop-
ment and metamorphoses of caligus,
referred to, 424 ; the testis and its se-
cretion in the decapodous crustaceans,
429-435 ; the mode of reproduction
of lost parts in the Crustacea, 471-
475 ; on the anatomy and develop-
ment of the cystic entozoa, 476-503
Granulations of surgical pathologists, in
reproduction of bone, 469
Gray cellular layer of the retina, 266
Growth and secretion, centripetal, 418
Gruby, microscopic character of morbid
products referred to, 378
Gymnorhynchits horridus in liver of sun-
fish, 494
four batteries in, 291
Hdbenula sulcata, 283 ; denticulate,,
284
Haemal arch, Goodsir's remarks on Pro-
fessor Owen's view of, 97-100
Haemaipod, Goodsir's term for a verte-
brate animal, 85
Haemome, hsematome, terms of Good-
sir's, 86
Hannover on .conferva of frog and newt,
350
Havers (Clopton) on vascular fringes of
synovial membranes, 437, 438
Haversian canals in bone, 406, 462 ; in-
flammatory changes, 468 ; glands or
synovial pads, 227, 228, 235
Hay (D. R.) examined the geometric
outline of the human body, 213-219
Head (vertebrate), morphological con-
stitution of its skeleton, 88-197
ffelianthus Merosus, electrical currents
in tubers of, 313
Helicoid curve of movement in knee-
joint, 238, 241
Helix algira, cells in kidney of, 413 ;
INDEX.
519
ff. aspersa, cells in liver, 414 ; kidney
of, 415
Helmholtz on reflected light acting on
the grey cellular layer of the retina,
269
Henle, System of Anatomy referred to,
231 ; on epithelium-cells of glands
and follicles, 412
Hip-joint, general mechanism of, 513,
514
Human anatomy supplies keys for mor-
phological solution of parts in pre-
sphenoidal sclerotome in birds, etc.,
157
Human body, beauty of, arising from
certain symmetrical and geometrical
forms, 215-219
Hunter (John), account of the Gymnotus
eleclricus referred to, 292 ; Natural
History of Teeth referred to 20, etc.
Hi/as, testis of, 430 ; spindle-shaped
cells, 432
Hydatula gadorum, Kathke, 497
INCISIVES (central), how they pass
through the gum, 37 ; (superior)
teeth, tardy development of, 45
Inductive philosophy promoted the ad-
vance of physical science, 206
Infant eight or nine months old, state of
teeth in, 24
Inflammation of membranes, 438
Infusorial animalcules on filaments of
conferva of gold-fish, 350
Intermaxillary bones and incisors, 46,
47
Internal lamella of Blake, 33
Internuncial cord in electrical fishes, 289
Intestinal glands, on a diseased condition
of the, 372-378
Intestinal villi, the structure and func-
tions of, 393-402
Ivory of elephant's tusks, musket-bullets,
etc., inclosed in, 56-65
JACOB'S membrane of retina, 274
Janthina fragilis, mantle and its secre-
tion, 416, 425
Joint-surfaces of mechanicians and of
organic structures, differences of, 246
Jonquil, electric current at time of
flowering, 315
KEY (Aston) on the ulcerative process
in joints referred to, 408
Kidney and liver, structure and patho-
logical changes in, 379-383 ; appendix
to this paper, 383-386 ; granular de-
generation of, 379-381
Kiernan, researches into the healthy and
morbid structiTre of human liver, 381
Klockner, gold ball found in tusk of
elephant, 57
Knee-joint, anatomy of human, 220-230 ;
mechanism of, 231-245
Knees in female brought together, 218
Knox (Dr.) on tooth-substances, 62 ; on
the troughs in gymnotus, 292 ; (F.)
tooth-germs in foetus of whale, 54
Kolliker on the rods and cones as the
seat of the impression of light in the
retina, 269
Lcemodipoda, testis in, 433
Lamina spiralis of the cochlea, 282-288
Land-crabs of tropics, 429
Langer forms continued screws from
upper articular surface of astragalus
in horse, etc., 237
Lathy rus tuberosus, electrical currents
in tubers of, 313
Law of the excitation of nerves by
electrical current, 337, 338 ; of
force, how made out by Sir Isaac
Newton, 212 ; of production, what
may prove to be, 213
Laws regulating the development of
pulps and sacs, and period of appear-
ance of each tooth-germ, 48-50
Lawrence on growth of orifices produced
by balls in ivory, 58, 59
Leaves, Becquerel's observations of
electrical currents in, 314
Leptopodia, testis of, 430
Leydig on structure of simple and com-
pound eyes, 279
Liebig on power possessed by vapours
of carrying along with them portions
of bodies which in their solid form
resist dissipation by very high tem-
peratures, 362
Light, mode in which it acts on the
retina, 273-281
Lily (white), electrical current at time
of flowering, 315
Limbs, Goodsir on the morphological
constitution of, 198-203 ; organ in
crabs which supplies germs for, 472
Limitary layer of the retina, 267
Liver, observations on structure and pa-
thology of, 381-386 ; the natural habi-
tat of the acephalocyst, 476 ; (human)
nucleated cells of, 415, 416
Logarithmic spiral in shells, 209-211 ;
probably the law at work in the in-
crease of organic bodies, 213
Loligo sagittata, secreting membrane of
ink-bag, 413 ; liver of, 415
520
INDEX.
Louis and Chomel on matter distending
intestinal glands, 378
Lymphatic glands, structure of, 439-444
Macroura (Crustacea), organs of genera-
tion in, 431, 433
Magnet formed by electricity of fish, 342
Malapterurus, electric batteries in, 293,
294, 302
Male and female figures, how they differ
in harmonic ratio, D. R. Hay's views,
217, 218
Malpighion secreting glands being formed
of tubes with blind extremities, 412
Mammary gland of bitch, 416
Mathematical modes of investigation in
the determination of organic forms,
two lectures on the employment of,
205-219 ; principles on which shells
are constructed, 209-211
Matteucci on the dependence of the
electromotor energy of electric appa-
ratus in fishes on the nervous centre,
300 ; electric properties in muscle
due to its own texture and not to
nerves, 323
Mechanism of knee-joint, Goodsir's me-
moir on, 231-245
Meckel's cartilage, 187-190
Membrane and gland, electric pheno-
mena in connection with, 319-322
Mercury, effects of, on teeth, 38
Metasomatomic openings defined, 85
Meyer, on the peculiar curvature of the
inner condyle of the. femur, 22 0-22 4,
232 ; his Mechanics of the Human
Skeleton referred to, 220, 232-234
Microcosm, electrical disturbances in,
represented by similar but grander
phenomena in macrocosm, 338
Milk incisives, growth of, 36
Milk-teeth, production of, 48, 50, 55
Modiola vulgaris, liver of, 414
Molars in man and elephant, their
growth, 41 ; the anterior permanent
molar the most remarkable tooth in
man, 45
Mollusca, Moseley on the logarithmic
curve in the shells of, 209-211 ; eye
in, how acted on, 280
Monitor-lizards, "palatines" in, 160
Morphological constitution of the skele-
ton of the vertebrate head, 88-197
Moseley (Professor) on the geometrical
formation of shells, 209-211
Mouth, position of, fundamental differ-
ences between morphological relations
of annulose and vertebrate nervous
systems, 80, 82
Movement (primary) or " along the
thread," what it means, 248 ; (second-
ary) or " across the thread," 248
Mucous membrane, electric relations of,
320, 322
Miiller on cyclostomous fishes, 174 ; on
absorption, 397 ; on secreting glands,
412
Miillerian filaments of the retina, 269 ;
not nervous structures, 270
Muscle, electric properties of, 322-331
Musket-bullets and other foreign bodies,
how inclosed in tusks of the elephant,
56-65
Musical harmony in proportions of human
frame, D. R. Hay's theory, 216-219
Myome, myotome, terms of Goodsir's,
86
Nautilus, the form of the shell in, 211
Nares, relative position of external and
internal, 165
Nasal chamber in bird, 169 ; fosste,
their constitution, 165-173 ; passage
of cyclostomous fishes, 173, 175
Nasmyth (A.) on resemblance of ossified
pulp to diseased ivory, 62
" Negative" movement in joints, 249
Nereis, biliary apparatus of, 415
Nerves of batteries in electrical fishes,
289-291 ; in gymnotus, 298
Nerve-filament, the doctrine of Du Bois
Reymond on, 276
Nerve, electric properties of, 331
Nervous centre in electrical fishes, 289 ;
force and electricity equivalent, 331 ;
system in the annulose and vertebrate
types, morphological relations of,
78-87
Neurome, neurotome, terms of Goodsir's,
86
Neuronaia monroi, 493 ; John Good-
sir's account of, 495-501
Neuropod, Goodsir's term for an annu-
lose animal, 85
Newton from the geometric forms made
out the law of the force, 212
Nobili on electric current in nerve and
muscle of the frog, 323, 328
Noise, sound heard merely as noise in
vestibule of ear, 287
Nostrils of chelonian more of the or-
nithic than mammalian conformation,
171 ; of crocodiles, peculiar position
of, 118, 119
Nucleated cell, secretion a function of,
413-416, 428
Nutritive centres of textures permanent,
390 ; of organs embryonic, 390
INDEX.
521
Oken, views on cephalic limbs held by
Carus, 193
Olfactory chambers in head of birds,
153 ; sense, its seat, 168
Operculum of the shell, its importance
in regulating the form, 210, 211
Opuntia, current passing from stamen
to pistil at time of flowering, 315
Organic electricity, present state of,
306-350
Organised and inorganised bodies, dif-
ference in the mode of studying, 207
Organs that have once acted an im-
portant part never altogether dis-
appear so long as they do not inter-
fere with other functions, 39
Osseous texture, 461
Ossific juice repairing injury in ele-
phant's tusk, Blumenbach's opinion,
58
Ossification round balls in tusks of
elephant, 60
Owen (Professor) on the relations of the
endo and exo-skeleton, 79 ; structure
of head of dodo, dinornis, apteryx, etc.,
152-154 ; views on limbs, remarks of
Goodsir on, 198 ; description of a
microscopic entozoon infesting the
muscles of the human body, referred
to, 494 ; on the anatomy of Distoma
clavatum, 499
Owl, bones of the head, 152
PACraion electrical diaphragms, 290,291,
292, 302, 303
Pagurus, generative organs of, 431, 432
Palatal arch and pterygoids in the bird
158, 160 ; in reptiles and amphibians,
160
Palate-bone of bird, lacertian, and am
phibian, 136
Parelectronomic layer of Du Bois Eey
mond, 327
Patella, movements and relations of, as
observed by Goodsir, 223-227
Patella vulgata, liver of, 415
Peach and apricot, electrical current in
315
Pecten opercularis, bile-like fluid in
pouches, 414
Pectoralina hebraica, a composite ani
mal, 360
Peptome, peptatome, terms of Goodsir's
86
Periosteum as an element in formation
and economy of bone, 463, 465, 470
Permanent teeth of independent origin,
51 ; developed from inner surface of
cavities of reserve, 53
2
eyer's glands, Boehm and Krause on,
413 ; patches, ulceration of, in con-
tinued fever, 372-378
Phallusia vulgaris, hepatic organ of,
415
Photaesthetic bodies of retina, 275, 278 ;
surface, 278
Photogenic rays, 277
Pig, follicular stage of dentition in, 53 ;
gastric glands in, Wasmann on, 413
Pirena prunum, hepatic organ of, 414
Pituitary body, Eathke on, 82
Placenta (human), Goodsir's memoir on
the structure of, 445-460
Plant, soil, and atmosphere, electrical
reactions of, 309
Polarisation of nerve, to what is it due ?
336
Positive" movement in joints, 249
Post-stomal cephalic sclerotomes, 175-
197
Potato, electrical currents in tubers, 313
Pouillet's experiments on electrical deve-
lopment in young plants, 308 ; in old
plants, 309
Prawn, seminal fluid, 434
Pre-sphenoidal sclerotome, 148-158 ; in
birds, 149-154 ; in chelonians, 154 ;
in crocodiles, 154 ; in lizards, 155 ;
in ophidians and batrachia, 155 ; in
fish, 156 ; haemal arch in fishes, 163
Primary or fibrous sclerome, 93 ; se-
creting cell, 417
Primitive dental groove, 27-30
Principal frontal of birds, what, 149
Proboscidian mammals, simplification of
sclerotome in, 111
Proboscis of elephant and tapir more
than a mere elongation of external
nose, 111
Progressive development, phases through
which the tooth-pulp passes, 30
Proximal margin in movements of joints,
248
Pterygoid in fishes, 164
Pulmonic blood, electric relations of,
322
Pulps and sacs of human teeth, their
origin and development, 1-52
Purkinje on secreting function of part of
the gland-ducts, 412
QUADRATE-JUGAL bone of bird, Owen's
analysis, 189
KABBIT, follicular stage of dentition in,
53
JRaia, tail of, peculiar structure on the
sides of, 295
M
522
INDEX.
Rathke on pituitary "body, 82 ; on bran
chial clefts and quadrilateral bodies
on each side of chorda dorsalis, 89
Ray, Hallman on the testicle of, 413
tail of, 295
Reflection of light from bottom of eye,
270
Reid (Dr. John) on placenta, obser-
vations of, 457, 458
Remak, observations on dorsal quadri-
lateral bodies, 89, 90
Reproduction of lost parts in the crus-
tacea, Harry Goodsir on, 471-475
" Reserved " and " restricted," terms
employed in distinguishing the ar-
ticular elements in their respective
conditions, 247, 261
Respiratory mucous membrane, electric
relations of, 322
Retina, memoir on the, 265-272 ; how
light acts on the, 273-281
Retzian tubes of ivory, 61
Retzius on microscopic structure of
dental substances, 62
Reymond (Du Bois), on the law of the
muscular current, 324; electric cur-
rents in nerves, 331-338
Rhinal sclerotome in mammals, 115 ;
rudimentary in crocodiles, 117
Right angle, division of, enables artist
to get a proper succession of lines in
drawing, 214, 215
Robin on organs in the tail of the ray
fishes, 297
Robison (Sir John), specimens of bullets
in ivory presented by, 56
Rods of retina, 265 ; seat of impression
of light, 269, 274 ; Goodsir's opinion
not nervous structures, 270, 274
Root, electrical currents in, 313
Rokitansky, on matter peculiar to typhus
fever, 378
Rudolphi on the troughs in gymnotus,
292 ; on the prisms in torpedo and
gymnotus, 301
Ruminants, follicular stage of dentition
in, 53-55
Ruysch figures bullets in ivory, 58
SACCULAB stage of dentition, 44
Sarcina ventriculi, history of a case in
which a fluid periodically ejected from
the stomach contained vegetable or-
ganisms of an undescribed form, 351-
371 ; definition of genus and species,
361 ; how its form is produced, 211
Savi on the elementary filaments of the
nerves in battery of electrical fishes,
290
Scseotrope movements, 260
Schonlein, " general pathology " re-
ferred to, 378
Schwann on the secreting organs of
mucous membranes, 412
Sclerome of Goodsir, 85 ; in vertebrate
embryo, its sources and modes of
origin, 88, 93 ; sclerotome, 85
Screw-configuration of articular surfaces
of elbow, ankle, and caleaneo-astraga-
loid joints, 237. ; movements in knee-
joint, 243-245
Scrofulous disease of joint, 410
Secondary dental groove, 30-41 ; teeth,
55
Secreting structures, Goodsir's memoir
on, 412-428
Secretion differs from absorption mor-
phologically, 398
Secretions, three orders of, 423
Semilunar cartilages of human knee-joint,
their movements and relations, as ob-
served by Goodsir, 227-229
Seminal secretion of decapod Crustacea,
development of, 427
Serous membranes, structure of, 436-438
Serres, 1'Anatomie et la Physiologie des
Dents, referred to, 22 ''.
Shaft of a long bone, on the mode of re-
production after death, 465
Sharpey (Dr.), on impregnated uterus,
452 ; on the entozoa of nerves of had-
dock and whiting, 496, 497
Sheep, follicular stage of dentition in,
53^; supra-renal, thymus, and thyroid
bodies in the embryo of, 68 ; entozoon
found in its brain, 487
Shells of molluscous animals examined
geometrically by Professor Moseley,
209
Simple eye, its physiological superiority
to compound eye, 281
Simplicity of natural law consists in the
comprehensiveness of its general prin-
ciples, 185
Skate, fusiform mass on each side of the
tail in, exhibiting all the structural
characteristics of an electrical battery,
295 ; nervous twigs, 299
Slough in soft parts separated from
living textures, 406
Somatome of Goodsir, 84
Spear-head found in tusk of elephant, 64
Spheroidal bodies on brain are entozoa,
495
Sphairidionacephalocystis, 487, 492, 503
Sphenoidal turbinated bones, 158
Spongiole of root of plant, an active
organ of growth and of absorption, 401
INDEX.
523
Sgualus cormMcus, testicle of, 416, 419-
422
Stages into which dentition is divided,
43
Stark (Dr.) on organs in the tail of the
rays, 296, 297
Stomach : fluid ejected from the stomach
of a patient which contained vegetable
organisms, 351, 371
Strix flammea, optic foramina in, 152
Sun, his relations to the earth and other
planetary bodies, 206
Supra-oesophagal ganglion, pre-stomal
character of, 86
Supra-renal bodies, 66-77
Syme (Professor) on the power of the
periosteum to form new bone, quoted,
465
Symmyotome, synhsematome, synneura-
tome, terms of Goodsir's, 86
Synovial pads of the human knee-joint,
their movements and relations, as
observed by Goodsir, 227, 228
Synpeptatome, syssclerotome, syssoma-
tome, terms of Goodsir's, 86
TEETH (human), origin and development
of the pulps and sacs, 1-52
Terms in morphology must be precise,
84
Thigh-muscles action of certain, 222 ;
and leg rotate in opposite directions at
the close of extension and commence-
ment of flexion, 234
Thomson (Dr. Allen) on primitive con-
dition of gastric and intestinal gland,
413 ; follicles of stomach and large
intestine originally closed vesicles,
426
Thymus, how formed, 66-77 ; Sir Astley
Cooper on, 74
Thyroid, a portion of the membrana
intermedia of Eeichert, 66
Tooth-sacs (permanent), 35
Tooth-substance, deposition of, in embryo
of sixteenth week, 18, 34
Torpedo, batteries in, 289 ; will of the
fish, 302
Transition-teeth, 55
Triangulares (Crustacea), generative
organs in, 429-433
Trichina spiralis, 493 ; Owen on its
cyst, 494
Tropceolum tuberosum, electrical currents
in tubers of, 313
Tufts of human placenta, 445-449
Tulip, electric descending current at
time of flowering, 315
Tumour : description of an erectile tu-
mour, 504, 505 ; of the testis, de-
scription of a congenital one, 506,
507
Turbinated shells, how their form is pro-
duced, 211
Turbines, the logarithmic spiral curve
possessed by these shells ascertained
by Professor Moseley, 209
Tusks of elephant, bullets and other
bodies inclosed in, 56-65
Tusk-pulp of elephant, wounding of, 60
Twin-elements, what Professor Goodsir
means by term, 247
ULCERATION, nature of, 404-407 ; in ar-
ticular cartilages, 408-411 ; of Peyer's
patches in continued fever, 372-378
Upper jaw dentition precedes that of
lower jaw, 45
Uraster rubens, secreting organ in sto-
mach, 414
Urine, where first formed, 379
Uterus, mucous membranes of, 452 ;
dissection of vessels, 457
VALENTIN, Handbuch, referred to, 11,
etc. ; on the structure of the laminae
in batteries of electric fishes, 290,
298 ; on the action of, 301
Vascular border in gum, 38
Vegetables, electrical phenomena in, 30 7-
318 ; organisms in fluid from stomach,
351-371
Vertebra (typical), applicability and
convenience of Professor Owen's terms,
95
Vertebrate type, on morphological rela-
tions of nervous system in, 78-87
Vertebrata, eye in, how acted on, 280
Vestibules of ear, sound heard merely as
noise, 287
Villi (intestinal), structure and functions
of, 393-402
Vision, organ of, there are three funda-
mental forms of, 273
Vomer, its complete development in
mammalia, 117
Vomerine sclerotome in mammals, 117 ;
in crocodiles, 118 ; in the lizards,
119 ; in birds, 119, 120 ; in chelonian
reptiles, 120, 121 ; in the osseous
fishes, 121, 122
WAGNER (Eudolph) on structure of ele-
mentary filaments of nerves in bat-
teries of electrical fishes, 290
Walrus, substance in pulp-cavities of
tusk, 62
Walsh on the electricity of the torpedo,
524
INDEX.
300 ; determined the shock to be of
the electric character in 1772, 318
Wartmann on electric currents in vege-
tables, 308, 314
Water decomposed by electricity of fish,
342 ; condition of water surrounding
the fish at the moment of discharge
of the electric organs, 343
Weber : the brothers Weber on the me-
chanism of the human knee-joint,
220, 231
White cellular layer of the retina, 266 ;
Bowman on, 268
Will of the electric fish determines flow
of nervous force into spaces of bat-
tery, 301
Wilson (Erasmus) on Eckinococcus ho-
minis, 480
Wilson (Dr. George), analysis of liquid
in which the Sarcina ventriculi was
found, 361-370
Wisdom-teeth, 40 ; sometimes decay at
an early period, 45
Wolffian bodies, formation of, 67
Wollaston (Dr.) on the agency of elec-
tricity on animal secretions referred
to, 319
Wounds in tusks of elephants, 63-65
YOUNG (Dr. Thomas) on cochlea being
a "micrometer of sound," 287; on
the electric force, 320
ZANTEDESCHI'S observations on electrical
condition of different plants when
flowering, 315
Printed by R. CLARK, Edinburgh.
mm
m '