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1 2 3

LABORATORY

OF THE

DEPARTMENT OF THE INSTITUTES OF MEDICINE,

MeGILL COLLEGE.

The following Practical Courses may be taken by Students : —

I. Practical Physiology, including practical exercises in Physio-
logical Chemistry and a series of demonstrations, with apparatus,
illustrating important physiological laws.

Winter Session — Saturdays, 2-4 P.M.

II. Normal Histology. — The examination and preparation of the

healthy tissues. Microscopes and reagents provided.

Winter Session — Bi-weekly.

III. Morbid Anatomy. — A series of demonstrations on the coarse
(macroscopic) appearance of organs and tissues in a diseased
state.

Winter Session — Saturdays, 10 A.M.

IV. Clinical Microscopy.— A course specially designed to meet
the requirements of the practitioner, including examination of
sputa, urine, blood in disease, tumours, &c.

Summer Session — Bi-weekly.

WILLIAM OSLER, M.D., Professor.

T. WESLEY MILLS, M.A., M.D,, Assistant.

DEPARTMENT OF INSTITUTES OF MEDICINE MeGILL COLLEGE.

STUDENTS' NOTES.

NORMAL HISTOLOGY

FOR

LABORATORY AND CLASS USE.

WM. OSLER, M.D.,

Member of the Royal College of Physicians, London; Fellow of the
Royal Microscopical Society, London; Professor of the Insti-
tutes of Medicine McGill University; Physician and
Pathologist to the General Hospital, Montreal.

MONTREAL:
DAWSON BROTHERS, PUBLISHERS.

1883.

¥%

P 'g rl

/yo

TO THE STUDENT.

A practical course on Normal Histology is advantageous in
many ways : it affords you a practical acquaintance with the appear-
ance and modes of preparation of tissues in health ; it familiarizes
you with the use of the Microscope, and it assists in the formation
of those habits of accurate observation which should form an
important part of your training. Keep in mind, from t'he outset,
that you are not to become Histologists, but Practitioners ; so
regard this course as one among many means to the end which
should be ever before you, viz., proficiency in the diagnosis and
treatment of disease. Once in active practice, and not a day will
pass without an opportunity of using the Microscope to assist in
the diagnosis of obscure affections. It is of equal importance with
the Stethoscope, the Opthalmoscope and the Laryngoscope, and
ignorant of its teachings you cannot practice with due credit to
yourself, or with full justice to your patients. To become expert
in its use requires time and patience — not more time, however,
than, with judicious economy, the hard-worked student can well
afford, and not more patience than should "possess the soul"
of any one who aspires to such a profession as medicine.

These Notes will also be, I hope, of use in the lecture-room
and in the weekly Demonstrations on Histology. For fuller details
in microscopic technology the student is referred to the manuals
of Schafer, Rutherford and Stirling ; for additional information on
the structure of tissues, to the works of Klein, Ranvier, Frey,
Strieker, Satterthwaite and others, which are accessible in the
Laboratory.

/VO/8

INTRODUCTION.

Jl i

The Microscope. The most essential requisite in histological work
is a good microscope, of a magnifying power of at least 300
diameters. The instrument which I, prefer, and which is used
in the Laboratory, McGill College, is the III. A. of Hartnack
(now Prazmowski), i Rue Bonaparte, Paris; it costs about $40.
Other microscopes which I can recommend are Swift's (Univer-
sity street, Tottenham Court Road, London), and Parkes'* (Bir-
mingham) ; Pillischer, of Bond street, London ; Zeiss, of Jena ;
and V^rick, of Paris.

The stand should be firm and solid ; the horse-shoe of
the Hartnack model is steadier, I think, than the tripod.

The stage should be plain, without other accessories than a
pair of clips to hold the glass slip when the pillar of the instru-
ment is bent at an angle. Moveable stages of all kinds are
unnecessary, and are greatly inferior to the fingers when once
properly educated by practice.

The pillar of the instrument is usually provided with a
hinge, but for the greater portion of the work of an histology
class the stage must be kept level.

The optical part of the instrument consists of the lens or
objective and the eye-piece or ocular. The lenses of foreign
makers are distinguished by numbers, i, 2, &c. ; those of
English makers by their focal length, i^-inch, i^-inch, &c. With
Hartnack's IIL A., Nos. 4 and 7, with Swift's or Parkes' a i-inch
and a ^th, are provided, and are designated respectively the high
and low powers. The No. 7 or the f^th is a high enough power for
the ordinary purposes of a medical student or practitioner. For
special studies, when higher powers are required, the No. 9 or

* Messrs. Frothringham & Workman, St. Paul street, Montreal, keep a supply of
this maker's instruments. 1 have recommended them to a number of medical men,
to whom they have given great satisfaction.

VIII

1 1 immersion of Hartnack or the F. of Zeiss may be used. An
immersion lens is one in which a minute drop of water, oil or gly-
cerine is placed between the lens and the top cover. The sharp-
ness of definition and the illumination is thereby increased.

The eye-pieces, of which two are usually provided, are num-
bered I, 2, 3, &c., in the foreign instruments, and A., B., &c., in
those of P^nglish makers. The shorter the eye-piece, the higher
the magnifying j)ower. Nos. 3 and 4 are usually provided with
Hartnack's III. A., and A. and B. with the English instruments.
When using a high objective it is best to have a low eye-piece.
The No. 7 r^artnack goes, in ordinary use, with the No. 3 eye-
piece, and gives a magnifying power of about 300 diameters.

The adjustments, two in number, the coarse and fine,
are the means by which the focus is obtained. The former is
effected by pushing down the tube which bears the ocular and
objective until it approximates the slide. 'I'iiis should be done
carefully, with a scrcnti-like motion, otherwise the tube is apt to
go down too fast. The brass must be kept quite bright, else
the motion is hard and jerky. In larger instruments this is
effected by means of a rack and pinion. When the objective is
brought to within a short distance of the slide, the fine adjust-
ment is used. This is usually in the form of a milled-head screw
at the upper part of the supporting pillar of the microscope, by
the rotation of which the horizontal piece bearing the tube is
slowly elevated or depressed.

Illnmination. ^y a mirror under the stage in the case of
transparent objects, and by a bidPs-eye condenser in opaque
specimens. The mirror is usually a little concave, and the
light is best reflected from the blue sky or a white cloud ; never
direct sunlight. For artificial illumination, an ordinary lamp
with a good flame will sufl^ce; a whiter light is obtained by
using a light-blue chimney-glass. A diaphragm is placed under
the stage, with apertures of various sizes, by which the amount
of light can be regulated. It is well to examine objects with
different degrees of illumination. With high powers use one of
. the smaller apertures.

The following details are to be followed in examining
an object, as a drop of milk .—See that the glass slip and

the top-cover are quite clean ; place the drop in the centre
of the former, and with the finger or foiceps apply one
edge of the top-cover to the margin of the drop, and let it
down slowly, so as to avoid enclosing air-bubbles. See that the
quantity is only just enough to fill the space between the top-
cover and the slide ; any superfluous fluid is to be absorbed by
blotting-paper. Place the slide on the stage, being careful to
lift up the tube, so as to get the objective out of the way.
Arrange the mirror for illumination, a little manipulation being
necessary to get the light properly reflected through the dia-
phragm. Then gently rotate the coarse adjustment until the
faint outline of the object on the slide can be seen, and with
the fine adjustment bring it clearly into view, or focus. Where
there is only a small quantity of material on the slide, it is
perhaps better for beginners to push the tube down until
the objective (No. 7) is about ^th of an inch from the
top-cover, and then use the fine adjustment. In the examina-
tion of specimens it is well to get into the habit of grasping the
edges of the slide firmly with the forefinger and thumb of the
left hand, and with those of the right the railled-head fine adjust-
ment. By this means the various parts of the slide can be
rapidly brought into view, and the focus quickly altered. In
removing the slide always lift the tube up.

Drawing. It is of paramount importance for the student to
learn to draw the various objects he sees, and for this purpose he
should provide himself with a sketch-book and an H. B. and 4 H
pencils. The rule is, draw the object just as it looks. The camera
lucida may be employed to ensure greater accuracy.

For the theory of the Microscope, consult Rutherford's
Manual ; for description of various microscopical accessories.
Carpenter's Text-book and the Histological part of Sanderson's
Hand-book for the Laboratory.

;ial

PREPARATION OF TISSUES.

Indifferent fluids. It is a good rule always to examine
specimens in a fresh state. For this purpose certain reagents
are used, which do not alter materially the appearance of the
tissues, and are called indifferent fluids. The chief of these are
solution of common salt, ^%,— the most useful and generally
employed ; blood serum, or aqueous humor from eyes of sheep
or ox, and blood serum with a {q^n drops of iodine— iodized
serum.

Teasing. Fresh specimens are usually examined after the
process oi teasing, an art of some delicacy and rarely well learned
by the student. Take a small bit of the tissue, and place it on a
slide with a small drop of salt solution or serum ; with one
needle fix it, and with the other tease away a small fragment, and
repeat this process until the portion is separated into minute
parts. In the case of a fibrous tissue separate the elements, as
far as possible, in the direction of the fibres. For transparent
objects tease on a dark background ; for stained specimens place
a piece of white paper beneath the slide. With a small drop of
fluid the bits can be more readily manipulated, and then, if
required, more can be added before mounting.

Hardening. Most tissues require to go through a process of harden-
ing, in order to render them firm enough to cut thin sections.
Two methods are employed : —

(i.) Freezing. Applicable to most tissues, and a very
speedy and convenient way. During the winter months in this
country it is only necessary to expose an organ to the air for a
few hours, or place it over night between the double windows,
and it freezes hard enough to cut sections with a cold razor.
One of the many forms of freezing microtomes serves the same
purpose, and has the advantage of being always available.
(2.) Various hardening fluids, the chief of which are :

Bichromate of potash, 2% solution, 20 grms. in a,ooo c.c.
of water. Solution should be changed every three or four days.
Hardens tissues in about three weeks.

MulUr's fluid. Bichromate of potash, 25 grms. ; sulphate
of soda, 10 grms. ; water, 2,000 c.c. A most useful fluid ; alters
the tissues very slightly ; hardens slowly, and does not require
to be changed so often.

Chromic add, Yt^ \.o \io/o solutions. It is best to make a
one per cent, solution, 10 grms in 1,000 c.c. of water, and dilute
this as required. It makes the tissues more brittle than the
bichromate or Miiller's solutions.

With these the rule is to put small bits of the tissue at first
into small quantity of the solution for a day, and then into a
large amount. Changing the fluid every fourth or fifth day is
often enougii, and in from two to three weeks I. , hardening
should be complete. The bits are then transferred to alcohol, in
which they can be kept until needed. After taking the bits out
of the above fluids it is well to let them soak in water for an hour
or so to remove the superfluous solution.

Chromic acid and spirit. Chromic acid ?/^%, i part;
methylated spirit, 2 parts. This fluid hardens more rapidly, in
from six to ten days, and is very generally employed for the
solid organs.

Bichromate of ammonia, 2% solution. Useful for brain
and cord.

Ammonium chromate, 5% solution. Hardens quickly, and
is specially used for the kidney to show Heidenhain's rods in the
cells, and also for demonstrating the inter-cellular net-work in
cells.

Alcohol. The ordinary methylated spirits obtained here can
be used, but absolute alcohol is better. It is well to put tissues
in dilute alcohol first, and then in stronger solution, and finally
in absolute alcohol. Some tissues, as mucosa of stomach, pancreas
and salivary glands may be put in the strong alcohol at once ;
but for most organs a preliminary hardening in Miiller's fluid or
the chromic acid and spirit solution is advisable.

XII

Picric acid-B. saturated watery solution-stains the tissue
of a yellow color. It removes the lime salts, and is used as a
aecalcifymg agent.

Osmic acid, %% solution. Hardens quickly, within 24
hours, and stams fatty matters and the myelin of nerve fibres
black. It is very useful for embryonic tissues, retina, nerve
fibres, &c. After hardening wash in water, and keep in alcohol.

Softening Solutions. To soften bone and teeth use picric acid
saturated solution ; specially good for foetal bone ; or chromic and
mtric acid fluid, % % chromic acid solution, and to each 200 c c
add 2 c.c. of nitric acid. It decalcifies bone in about two weeks
if solution is changed once or twice. After softening, wash
thoroughly to get rid of the acid, and then transfer to spirit.

Dissociating Fluids. These are useful for separating the elements
of the tissue or softening the cement substance, so that the fibres
can be more readily teased. Ihe most suitable are :—

Iodized serum, very dilute chromic acid, and bichromate of
potash solutions, i to 5,000 ; dilute alcohol, i to 2 parts of water.
Very small bits should be placed in the fluid, and usually
twenty-four or thirty-six hours is sufficient for the process.

Cutting Sections. Tissues hardened in the above-mentioned ways
are ready for section which is most conveniently done "by
hand " with an ordinary razor; one of those " made for the anny,"
with a thin broad blade, is the best. If the bit is large enough
it may be held in the hand ; if small it must be enclosed in some
easily cut material of about the same consistence as itself. For
this purpose a convenient way is to make a slit in a piece of
carrot or elder pith, or, better still, a bit of hardened liver, and
enclose the tissue to be cut. Usually some form of imbedding
mixture is employed, either white wax and olive oil, equal parts;
or paraffine four parts, lard, one part. Cacao butter or gum'
may be used in the case of some delicate tissues, and in embryo-
logical work.

In imbedding proceed as follows :— Make a small oblong
box of paper, i>^ x ^ inches, and fill it with the melted
mixture, which must not be too hot. Take the bit of tissue from

XIII

the spirit, dry it thoroughly with blotting paper, and fix it in the
wax and oil, near one end of the box, by means of a needle ;
then pour in enough of the mixture to cover the specimen ; set
aside for a few minutes until the tluid becomes firm, when the
paper may be removed.

In cutting sections attend to the following directions: —
Hold the wax mass in the left hand, between the fore-
finger and thumb, the razor in the right hand, grasped with
the fingers and thumb, not held tightly in the palm. Cut
rapidly from left to right, drawing the razor from heel to tip.
The sections can be floated off" the razor into spirit, with which,
also, the blade must be kept constantly wetted. Keep the
surface of the wax mass as level as possible. The razor must be
very sharp, and requires frequent stropping. To become a
successful section-cutter requires practice and some little dexte-
rity. It is a good plan for the student to practice for some time
on a large bit of hardened liver.

For cutting a large number of sections microtomes are
employed, the chief of which are those of Rutherford, Williams,
Schiefferdecker, and Ranvier. They are usually adapted for
freezing with a mixture of snow and ice ; some are arranged for
freezing with an ether spray.

Staining. In order to demonstrate details of structure it is essential
that the sections should be steeped in some coloring fluid. Of
these, the two most serviceable are carmine and logwood.

Carmine. Beale's fluid is very useful for fresh specimens,
and is thus prepared : Dissolve carmine, grm. i, in liq. ammon.
fort, 3 c.c, gently warm, and add aqua, distillat., 120 c.c, and
then filter. Add best glycerine, 30 c.c, and rectified spirit, 120
c.c. Keep in well-stoppered bottle.

Bits of tissue placed in this fluid stain in from twelve to
twenty-four hours.

Klein's formula is as follows : —

Carmine, grms. 2 ; rub up with aqua, distillat., and then add
liq. ammon. fort., c.c. 4., and aqua, distillat., c.c. 48. Mix and
filter. Keep in a stoppered bottle. For staining, one drop of
this in nine or ten of water. Sections from alcohol tint in about
Sixteen nours.

''M

XIV

For rapid staining the sections may be placed in the
undiluted fluid, in which they tint in a few minutes.

Logwood. I prefer the fluid made after Klein's formula. It
is very constant, and the tint is a good violet. The solution is
made as follows : Extract. Haematox, grms. 6 ; alumen, grms. i8.
Mix thoroughly in a mortar. Add gradually, whilst stirring :
Aqua distillat., c.c. 28. Filter, and to the filtrate add spirit,
rect. 5i.

For staining, add five or six drops to half a watch-glass of
water ; about dilute enough to enable print to be read through
the solution. The dilute fluid must always be filtered. Sections
from alcohol stain in from ten to fifteen minutes.

Other useful dyes are Picro-carmine, which has the advan-
tage of giving a double tint to the tissues, some parts of which
are stained yellow by the picric acid, others red, by the carmine.
Thus the stroma of the frog's blood-corpuscles is stained yellow,
and the nucleus red.

Among the aniline dyes* are several of great value, as
Mythyl-aniline, used as a strong watery solution. It gives a
double stain, a red violet and a blue violet. It is most service-
able in the examination of tissues which have undergone the
pathological change known as amyloid degeneration. Any
elements affected in this way are tinted red violet, the healthy
parts blue violet. Sections can be mounted in Parrant's solution
or glycerine — not in balsam, as the oil of cloves destroys the
color.

Aniline blue-black, i % solution in water ; very useful for
nerve tissues.

Aniline blue, Iodine green and Rosein are other dyes occa-
sionally used.

Magenta (rosaniline nitrate) is useful for tinting fresh tissues,
and in the irrigation of specimens when under observation.

Silver nitrate — Y2-% % solution. It stains the cement
substance between the cells and the intercellular substance of
connective tissue and cartilage, the black oxide being deposited
under the action of light. Tissues must be fresh, and should be

* R. & J. Beck, of Philadelphia, keep a good supply of all staining fluids.

laced in the

i formula. It
e solution is
en, gttns. i8.
'1st stirring:
s add spirit.

;ratch-glass of
read through
:d. Sections

s the advan-
irts of which
the carmine,
ained yellow,

at value, as
It gives a
most service-
dergone the
ration. Any
;, the healthy
ant's solution
destroys the

:ry useful for

tx dyes occa-

fresh tissues,
vation.

the cement
substance of
ng deposited
id should be

\% fluids.

first washed in distilled water to remove the chlorides, and then
placed in the solution for five or ten minutes until they have a
greyish-white appearance. Remove, wash in v/ater, and expose
to bright light, when the tissue becomes brown, owing to a pre-
cipitation of the silver.

Gold chloride. 3^-2 % solutions. Of great service in
staining nerve fibrils and connective tissue cells. Tissues require
to be steeped in it for half an hour to an hour, then expose to
the light in water slightly acidulated with acetic acid. Stirling
recommends the preliminary steeping of the tissue, as the cornea,
in lemon juice for five minutes, then in the gold for half an hour ;
wash, and place in a mixture of formic acid, one part to four of
water. In twenty-four hours the gold is completely reduced.

Osmic acid. ^-^ % solution. Hardens as well as stains.
Useful for nerve fibres, the myelin of which it blackens, and for
fatty tissues.

For details of double and treble staining the advanced
student may consult the work of Mr. Henage Gibbes.

Mounting. Sections which have been hardened in alcohol and
stained are, as a rule, mounted in dammar or Canada balsam.
The method of procedure is as follows : —

(i.) Remove from the staining fluid to water, in order to
wash away the superfluous dye. A minute or two is suflicient.

(2.) Transfer to alcohol— absolute is preferable. In this
the section can remain for an indefinite period, but a few minutes
will suffice to drive out the water.

(3.) Pick one or two of the thinnest sections, and place
them on the centre of a glass slip ; absorb the superfluous spirit
with blotting paper, and add a drop of oil of cloves, which
gradually clarifies the section by displacing the alcohol. A little
practice soon enables one to tell when the specimen is sufficiently
translucent.

(4.) , Absorb the oil of cloves, and add a drop of balsam or
dammar, and apply the top cover, being careful to exclude air-
bubblco.

Dammar is made as follows : Mix equal parts of mastic,
dammar, chloroform and turpentine, and filter.

% -

i t,

XVI

The Canada Balsam is made by mixing equal parts of good
Canada balsam and chloroform, and warm ; then filter.

Many preparations are mounted /resh from water or staining
fluid in glycerine, glycerine jelly, or Farrant's solution, and they
often show the minute details better than in balsam.

Farranfs solution consists of equal parts of glycerine and a
watery solution (saturated) of arsenious acid. To this add gum-
arabic, and allow the mixture to stand for several weeks, when it
is filtered, and is then ready for use. It has the advantage over
glycerine that it becomes hard, and so fixes the top cover. Bits
of fresh tissues stained in Beale's carmine and mounted in glyce-
rine will keep for years, if properly sealed at the edges. I have
slides prepared in this way twelve years ago, as good now as
when mounted.

To cement the edges of glycerine slides use balsam or
gold-size, which may be applied with a small camel-hair brush.
Be careful to remove all the superfluous glycerine from the
margin of the top cover, otherwise the gold-size will not stick,
and the preparation will eventually leak.

Carefully label each specimen, and keep the slides flat not

on their edges.

The student will need the following : —

Pair of small, fine-pointed scissors ; fine-pointed forceps ;
two needles in handles ; a razor ; a section-lifter, made by flat-
tening out the end of a bit of copper wire ; glass slips and top-
covers; watch glasses {j4 dozen) ; ladels, and a small box with
trays, capable of holding loo slides.

••■ ■

NORMAL HISTOLOGY.

AIR BUBBLES, GRANULES, &e.

Air Bubbles. Examine drop of saliva. Most of them are circular ;
border is dark, centre clear. Press top cover down and get a
variety of irregular forms. Study carefully, as they are of com-
mon occurrence in slides.

Oil Drops. Milk; circular globules of variable size ; contrast with
air bubbles. Yolk of egg; still smaller droplets of fat, with large
yolk spheres among them. Chyle, from Thoracic duct ; fine
molecular fat.

Granules. Rub up gamboge or Indian ink with water. Fine
granule has no light centre ; coarse granule has light centre and
dark border. Granules in fluid exhibit Brownian or molecular
motion, due to thermal currents.

Fibres. Cotton, flat, twisted ; linen, straight, often fissured ; wool,
cylindrical, with characteristic imbrications ; woody ; examine
slice of lead pencil, bits of boiled cabbage, turnip and carrot.

Dust. Examine slides of dust collected from different localities.
Note the great diversity of irregular particles, bits of hairs and
fibres of various sorts.

Starch. — Potato ; scrape cut surface. Observe concentric lamina-
tion ; nilus, so-called nucleus, is eccentric. Add dilute iodine.
Gra;., --^ are large, shaped like an oyster shell. Wheat) grains
smaller, striae faint, shape round or lenticular. Examine also
rice, arrowroot, sago and oatmeal.

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PROTOPLASM; CELLS.

Typical Animal Cell. Tiny mass of gelatinous substance, proto-
plasm, which is contractile and in which a nucleus can commonly
be seen. There may or may not be an investing membrane, cell
wall.

Study it in (i) the Amceba or Proteus animalcule, from
meat or hay infusion, or stagnant water. Observe outer hyaline
border, ectosarc, inner granular part, endosarc ; nucleus ; con-
tractile vesicle, a clear space which appears and disappears ;
foreign bodies, diatoms, &c., inside it ; change of form by pro-
cesses or pseudopodia; change of place, locomotion. Sketch
at intervals of 30 seconds.

(2) White blood corpuscle (blood amceba), vide infra.

These two bodies form the most suitable objects for study-
ing the simple undifferentiated animal cell. The ultimate
structure of protoplasm is reticular (intra-cellular network of
Klein and Heitzmann). To see, examine superficial cuticular
layer of frog or newt, after hardening in alcohol and staining in
logwood.

Cells of the adult body are arranged in the form of tissues,
as epithelium, gland tissues, etc. They do not often present
a definite cell wall, with double contour, but the outer layer of
protoplasm is more condensed and hardened. A delicate
investing membrane can be seen in some epithelial cells. In
many structures the cells have become differentiated to such a
- degree as to be scarcely recognizable ; for example, muscle and
nerve fibres.

Vegetable Cell, Only the very young cells of the embryo resemble
the typical animal cell. All others have a distinct cell wall. Ex-
amine edge cells of leaf of Vallisneria. Observe cell wall, double
contour ; clear or slightly granular cell contents with a few green

rectangular cells for the rotation of the protoplasm— o'^/<;«>.
The chlorophyl grains are carried in the protoplasmic currents.
Examine cells of thin cuticle of sheath of onion. Observe the
currents of protoplasm radiating from nucleus.

Cell Multiplication. Fission. May be seen occasionally in white
blood corpuscle. In slipper animalcule {Paramecium aurelia)
can be well followed. Get from gelatinous scum which forms
in meat infusion after 4 or 5 days. Consult Klein's Atlas for
neuclear changes in proliferating cells.

Gemmation, budding. Yeast plant ; vide infra.
Endogenous mode ; fission within cell membrane ; look for
m many unicellular plants, and in ova of snails and many
entozoa.

Vacuolation. Examine preparation of mesoblast of embryo
chick, or bit of rapidly growing sarcoma or cancer ; clear
spaces form in the protoplasm of the cell, and within this new
cells originate either as buds from the wall or perhaps from the
nucleus.

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FUNGI.

Their study important ; (a) in relation to certain skin diseases ; {b)
as agents in fermentation ; (i) as the supposed germs in many
diseases.

Lower forms divided by Nageli into three groups : —

( 1 ) Moulds. Examine common mould, PenicilHum glaucunu
Observe mycelium, dense felt-work of interlacing fibres ; hyphce,
the individual filaments of the mycelium, each hypha consisting
of elongated cells with partitions between them ; vacuoles in the
protoplasm ; aerial hyphae bearing spores or conidia.

The Achorion Schonleini oi Favus, Trichophyton tonsurus of
Ringworm, Microsporon furfur of Pityriasis vesicolor and O'idium
albicans of Thrush belong to this group.

(2) Sprouting Fungi, Saccharomycetes. Examine drop of
yeast. Observe unicellular bodies, the Torula or S. cerevisiae.
Some are single, others arranged in chains. Each consists of
granular protoplasm (with vacuoles) surrounded by a cell wall.
Irrigate with magenta, protoplasm only stains. Note the buds or
gemmae ; they increase by gemmation.

These little bodies are the active agents in alcoholic fer-
mentation ; they require O, and to get it have the power of
breaking up such compounds as sugar, and in the process the
constituent atoms of sugar re-arrange themselves into molecules
of ethyl alcohol and carbonic dioxide.

(3) Cleft-Fungi., Schizomycetes, — Bacteria. Examine hay or
meat infusion. Most of the forms can be seen in " fur" on the
tongue. The following varieties are distinguished : —

{a) Micrococci or spherical bacteria. Examine epithelium
of tongue. Observe among the scales, some which are very
darkly granular, being infiltrated with minute spherical, motion-
less bodies, which resist the action of aether and acetic acid.
They often occur in colonies or groups, and are common in all
decomposing organic matters.

(d) Elongated Bacteria. Bacterium termo. Examine any
decomposing infusion. Minute rod-shaped bodies, often in
couples ; length about twice or thrice the breadth ; they move
with an irregular progressive motion.

Examine the scum in top of decomposing infusion. Observe
Bacteria, spherical and elongated, imbedded in a gelatinous
matrix.

{c) Bacillus. Examine hay infusion ; straight filaments,
longer than Bacterium, jointed ; motile : B. anthracis of Splenic
fever resembles closely and perhaps is only a variety of B. subtilis
of the hay infusion. Bacilli filaments— often called leptothrix—
occur in " fur " of tongue.

{d) Vibrio; resembles the bacillus, but it is bent at the joints.
Motion is undulating.

(<?) Spirillum ; spiral filaments, unjointed ; motion screw-
like, often rapid.

The members of the two last groups constitute what are
known as the morphological or organized ferments, in contra-
distinction to the chemical or unorganized, as pepsin.

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BLOOD.

Human. To get drop, compress firmly the base of last phalanyx of
ring finger with the thumb and other fingers, and prick the
congested pad with a sharp needle. Try to proportion the size
of the drop so as to form a thin uniform layer beneath the top
cover; if too thick a layer, absorb with blotting paper. Watch
the corpuscles running together to form rolls or rouleaux —
process of fiumimilation. If layer is too thin this cannot take
place, and if too thick it is not well seen. In blood during high
fever and in some violent diseases the corpuscles do not form
rouleaux, but aggregate into irregular clumps.

Observe the following elements : —

Red Corpuscles. Circular biconcave disks. Watch an
individual corpuscle and cause it to roll over by touching the
top cover ; in profile it is a short, blunt rod ; the depressed
centres and thick edges can be well seen. Owing to its bicon-
cavity it presents a dark centre and light border, and vice versa,
as the focus is changed. Do not mistake this appearance for a
nucleus ; color a light reddish yellow. Corpuscle is a semi-solid,
viscous mass, without cell membrane or nucleus, and consists of
a uniform stroma infiltrated with a coloring matter, haemoglobin.
Measure ; average diameter ^nW to j-fi'dTs of an inch, or 7 • 5 to 8 mic-
romillimeters. Smaller forms are not Uiicommon in some healthy
individuals, while in certain diseases very small red corpuscles
(microcytes) are met with, -uW to Wcrj of an inch. On the other
hand, larger forms may pccur, ygW to -r^-^ of an inch (giant
forms).

Action of reagents. Add water ; coloring matter diffuses,
and leaves the pale stroma. Corpuscle seen then with difficulty.
Study carefully, as these decolorized forms are frequently seen
in urine and ejecla.

Add salt solution (i or 2 per cent.) ; rouleaux do not form.
Corouscles become irregular, with iaeeed edffes. rrenated.. .Same

is seen if slide is exposed for a few minutes before the top cover
is put on.

Add I per cent solution of Tanin ; coloring matter separates
from the stroma and collects at the margin in one or two small
dots.

White corpuscles. Proportion to colored ibout i to 400 or
500. Look for them in the clear spaces of the rouleaux ; small
masses of granular protoplasm, circular when first seen ; a little
larger than red corpuscle, but the size is very variable. Nucleus
often indistinct. Amceboid movement begins a few minutes after
withdrawal. Corpuscle attaches itself to the glass, and become
flattened ; outline gets irregular from the protrusion of processes.
To appreciate the changes, sketch at intervals of a minute. A
slow creeping movement takes place. Corpuscle may become
very flat ; note then the finely granular nature of the protoplasm,
the nucleus, and often small vaculoes or clear spaces. The
movement takes place slowly at ordinary temperatures, and is
much more lively on the warm stage. A corpuscle with very
coarse, dark granules, only partially filling the protoplasm, may
sometimes be seen.

Examine mucous corpuscle from mucus of nose or mouth,
or from mucus-cloud of urine, and pus corpuscles from abscess.
They resemble closely the white blood corpuscle, and when
warmed display amceboid changes. The term leucocyte is
applied to these cells indifferently.

Action of reagents. Water causes the corpuscle to
become pale and swell up. Acetic acid makes the nuclei very
distinct. Magenta stains them. Atropia i to 2 % causes them
to throw out peculiar, hyaline processes (Osier, Quart. Journal,
Micr. 1874). A similar appearance is sometimes seen in
mucous and pus corpuscles in urine.

Feeding white corpuscles. This is best done with newts
blood. Add salt solution, in which fine particles of carmine or
Indian ink are suspended, to a drop of blood ; surround top
cover with parafine, and, if human blood, place on warm stage.
The corpuscles are seen to take up the dark granules into their
With newts blood nrilk globulus may be substituted

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for the Indian ink. A striking experiment, which sometimes
succeeds with active corpuscles of frog or newt, is to mix the
blood with a tiny drop of human blood, the red corpuscles of
which may be " eaten " by the colorless cells. I have seen a
colorless corpuscle of the newt with four red corpuscles in its
interior.

Study in connection with this the following : —

(i) The phlegm first hawked up in the morning ; many of
the mucus cells contain dark grains which they have ingested.

(2) Specimen of carbonized lung, or, better still, of lung in
Anthracosis. Note how many of the carbon grains SlXQ fixed in
cells, some of which may be stretched and deformed to acctn/jruu-
date a large bit.

(3) Specimen of tissue near a recent extravasation. Note
how many of the connective tissue cells have taken up the blood
corpuscles. Section of brown induration of lung illustrates the
same thing.

Fibrinfibrils. Within two or three minutes after with-
drawal, the blood drop coagulates by the separation of the
fibrin, the delicate fibres of which are seen to pass in the clear
spaces between the rouleaux. Beginners often have difficulty in
seeing them. Sometimes the fibres are coarse, and the net work
very dense ; this is particularly well seen in blood of patients
with pyaemia.

Schultze's Granule Masses. In the blood of most persons,
irregular aggregations of colorless granules can be seen in variable
numbers. The masses range in size from a colorless blood cor-
puscle to collections 1 5 or 20 times as \ r t They are usually
regarded as represeiuing dibris of co^ ;*1 'puscles, ou'. I

have shown that they are aggregation l: .ijautc discoid bodies,
the nature of which is as yet unknown. They abound in many
cachectic states and in the blood of many animals, notably young
rats. Consult Schultze, Arch. f. Micros. Anat. Bd. I. ; Riess,
Reichert's Archiv, 1872. Osier, Proceedings of Royal Soc. 1874.)

An hour or so after eating the blood often presents numerous

Nucleated red blood corpuscles. Examine blood of foetus or
new-horn child. Here and there among the or(hnary forms, a
colored corpuscle may be found with a granular nucleus. They
are comnu-nly larger than the non-nucleated corpuscles. In
adults they are never found in the blood in health, but I have
met with them in cases Leucocythemia and in Pernicious
Anajmia. They abound in ordinary red marrow which forms the
most suitable object for their examination. In this tissue they are
regarded as transitional forms between the colorless marrow
cells and colored elements. Vide Marrow.

OrHEft Mammals. All have blood elements similar to those of man,
red, circular disks, except in camel tribe, in which corpuscles
are elliptical. There is, however, a great difference in size.
Measurements in micro-millimetres are as follows : Dog, 7 • 30 ;
Ape, 7 "35; Rabbit, 6*90; Sheep, 5*00; Horse, 5*43; Ox,
5*95; Cat, 5 • 50. Measure five corpuscles each of blood of cat,
dog and man.

Birds, Reptiles, Amphibia and Fishes. Red corpuscles are oval
and nucleated, the nucleus central, and causes a bulging on
either side of the cell. Examine a slide of each. Frogs blood
is particularlj' suitable for study of ama'boid movements of
colorless elements and the action of reagents. Still better are
the enormous corpuscles of the Menobranchus lateralis — the
large " lizard of the lakes," common in the rivers and lakes of
this continent.

Blood Counting. Estimate number of red globules in a cubic
millimetre with Cowers Haemacytometer or Malassez's Compte
Globule. Average number per cubic mill, 5,000,000.

Color Estimation. Use apparatus of Cowers or of Quincke.

Blood Crystals. Ifcemoglobin. Add small drop of rats blood to
a drop of water, put on a top cover and surround with parafine.
Haemoglobin diffuses from the corpuscle and crystallizes, at first
in small needles, which in time become large and form beautiful
stellate masses.

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Blood of guinea-pig may be treated in same way. The
crystals do not keep well, but if mounted dry or in balsam may
retain shape for some time.

Healthy human blood does not crystalize readily. From
blood in Leucocythaemia beautiful crystals may be obtained.

Hcemin. Crystals of this derived coloring matter may be
got in the following way : Dry a drop of blood on a slide, add a
few grains of finely powdered salt, put on top cover and let a
few drops of acetic acid run under ; warm gently over spirit
lamp until bubbles are developed. When examined, a number
of short prismatic crystals of a deep red color may be seen.
Sometimes the acid must be added again or even a third time,
and the slide again warmed before the crystals appear. This
forms an important test for blood stains, as the presence of the
crystals is positive evidence of the presence of blood, though, of
course, it affords no infonnation as to the creature from which it
was derived.

Hcematoidin, examine corpus luieum, or any old extrava-
sation.

'• I

EPITHELIUM.

Squamous. Examine (i) scraping of surface of tongue ; Observe
large flattened cells isolated or in groups of 4 to 8 ; edges often
folded. Nucleus small, centric.

(2) Vaginal mucus — cells have same appearance, often more
folded.

(3) Cuticle of Frog — stain in carmine, mount in glycerine.
Observe cells in contact, forming a continuous membrane, nuclei
stained.

(4) Examine section of skin or cornea to see stratification
of epithelium and gradual flattening of the cells as the suiface
is approached.

The squamous lining of serous membranes, blood and lymph
vessels and lymph spaces is known as endothelium.

Demonstrate as follows by the silver method. Kill the
animal, rabbit or frog, by bleeding; pencil the omentum or
mesentery with y^ % solution of silver nitrate, or, better,
immerse in the solution for 5 or 10 minutes. Wash in water,
expose to light until membrane becomes brown. Cut into small
pieces, float from the water on to slide, absorb the water, and
cover with and mount in glycerine. When examined, the silver
is found to have stained black the uniting material between the
cells, which are in this way beautifully mapped out. The nuclei
are not stained. Note that the cells from only a single layer, and
are not stratified as in epiliielium. To demonstrate endothelium
of lymphatics, kill rabbit by bleeding ; brush central tendon of
diaphragm with salt solution, and then pour over it ^ % silver
solution, and allow it to remain for 8 or 10 minutes ; excise tendon
and expose to light in distilled water. Cut pieces and mount,
silvered side up, in glycerine.

Glandular. Tease bit of deeper part of mucosa of stomach in salt
solution. Cells are spheroidal. Examine teased bits or scrapings
of liver and kidney. Cells are irregular in shape, protoplasm
granular, nuclei distinct.

;f f. .

Columnar. Tease very finely bit of mucosa of intestine of recently
killed animal. Cells are cylindrical, tapering ; ends pointed or
bifid ; base presents a seam or hem, which with very high power
is seen to be striated. Protoplasm finely granular, nucleus oval,
well defined. Cells are often seen in groups, and when looked
at with bases uppermost they present a beautiful mosaic. These
cells are very delicate, and the mucosa may require to be soaked
in bichromate of potash for 24 hours. Good specimens may be
obtained from intestine of child. Cells with swollen bases, or
with basal hem removed, can be seen ; they are called chalice or
goblet cells, and result from the transformation of the protoplasm
into mucin, which svvells and may rupture the base of the cell.

Transitional. Scraping of human bladder or pelvis of kidney.
Observe flattened cells, with curved markings, granular proto-
plasm and large nuclei ; others club-shaped with long tail-like
processes, others again oval in shape. Study carefully, as all
varieties are frequently met with in the urine.

Ciliated. Obtain from mouth of frog, gill or beard of oyster, or
trachea of recently killed animal. Examine in salt solution.
May be either spheroidal or columnar. The cilia are in constant
motion, and cannot well be seen until the movement slackens or
stops, when they appear as delicate hair-like outgrowths from
the free border of the cell.

-III

!■

CONNECTIVE TISSUES.

Areolar, fibrous and elastic tissues, cartilage, bone and dentine are
grouped together in this category. They all develop from the
mesoblast, and frequently pass by substitution into one another.

Areolar Tissue. Snip off a small bit of the subcutaneous tissue of
a young animal and spread out carefully on glass slip, to which
it will adhere and remain extended ; add salt solution and cover.
Observe the delicate fibres passing in all directions, some single,
others in wavy bundles. Numerous interspaces, or areolae,
filled with lymph, exist between the fibres, and in this the con-
nective tissue corpuscles can be seen ; which are of two kinds,
(t) the amoeboid and (2) the fixed. Former are round, and
resemble the colorless blood corpuscles, and are probably
derived from the blood. The fixed are of very various shapes —
spindles with long fibrils attached, or flat plate-like cells, with
longitudinal divisions. Add acetic acid; the areolar fibres
swell up and become indistinct, the corpuscles become more
distinct.

The following tissues may be studied in connection with
this : Mucoid or gelatinous tissue, which is found in the umbilical
cord (Wharton's Jelly), in foetal skin and in vitreous humour.
The tissue yields mucin on boiling. Tease bit of navel string in
salt solution ; observe the branching and anastomosing cells
forming a sort of reticular net-work, in the meshes of which is
the mucoid material.

Adenoid tissstie^ which forms the supporting framework
of lymph glands and spleen and exists as diffuse areas in other
parts. It consists of a dense net-work of fine fibrils, the
meslies of which are closely filled with the lymph cells, which
must be removed before the fibres can be seen. At the nodal
points in the reticulum, nuclei are seen, but these probably
belong to endothelial cells applied to the fibres. Vide lymph
glands.

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Neuroglia. The delicate net-work of fibres which supports
the elements of the central nervous system. It appears to par-
take rather of the nature of elastic tissue. Examine transverse
section of white substance of sp. cord.

White Fibrous Tissue. Exists in tendons, ligaments and fibrous
membranes. Consists of fasciculi or bundles of fibres, the
ultimate elements of which are parallel fibrils, identical with
those of areolar tissue.

Tease finely a small bit of any tendon, then add salt solution
and cover. Note the wavy, parallel course of the fibres. The
fibrils are indistinct, as they are united by a cement substance.
Dilute acetic acid, i per cent., brings out oval nuclei. The
intrafascicular spaces — which are lymph channels — with the
tendon corpuscles can be well seen by cutting a transverse
section of dried tendo Achillis ; stain in Beale's carmine fluid,
and mount in glycerine.

Elastic Tissue. Tease bit of ligamentum nuchae of sheep in salt
solution. Fibres are coarse, branch and anastomose ; ends
curled. Add acetic acid ; no change. Scrape off mucosa of
trachea, and then strip off thin submucous tissue. Observe fine
net-work of elastic fibres. Examine elastic layer of intima of
artery — fenestrated coat of Henle. For continuous elastic
membrane, study anterior lamina of cornea. In ordinary areolar
tissue, after the addition of acetic acid, elastic fibrils may fre-
quently be seen.

Adipose Tissue. Study silver preparation of mesentery. Numerous
fat cells enclosed in a sort of mesh work of areolar tissue. Each
cefl- Consists of a membraneous vesicle filled with oil; often
• radiating crystals of margarin can be seen. Stain a bit of omen-
tum in Beale's fluid, and mount in glycerine; the nuclei
of the fat cells appear at one pole. Study in sub-cutaneous
tissue of young rats the gradual conversion of the connective
tissue corpuscles into fat cells, by the development of oil drops
in the protoplasm.

Pigment Tissue. Examine section of retina, the outermost layer of
which consisted of flattened polygonal pigment cells. In rete
mucosum of skin, cells are spheroidal. Tease bit of choroid of
pig for stellate pigment cells. Examine tail of tadpole or web
of frog's foot.

■tm

Cartilage. Protoplasmic cells imbedded in a matrix of variable
character.

Varieties are ; Cellular, Hyaline, Fibrous and Elastic.

Cellular. Examine (i) drum of ear of small frog. Cells
closely packed, with little or no intervening matrix. . (2) Section
of chorda dorsalis of embryo.

Hyaline. Exists in laryngeal, tracheal, costal, articular and
embryonal cartilages. Cut thin sections with a razor and
examine fresh, in serum. Cells fill the spaces in the matrix,
often 2 or 3 in one lacuna. When fresh the nuclei are large and
distinct ; the protoplasm is in close contact with the matrix, but
it soon shrinks away unless immersed in some fluid, as auric
chloride, which fixes them in position. In costal cartilages, oil
drops are common in the cells. In epiphysal cartilage of tibia
of young animal, the cells are fusiform, or elongated. In ossi-
fying cartilage they are grouped in parallel rows. The matrix is
homogeneous, or finely granular, with a dim ground-glass appear-
ance. Picric acid preparation of human costal cartilage shows
zonular arrangement of matrix round the cells. It is probable
that the matrix is interpenetrated with a net-work of lymphatic
lacunae and canals.

Fibro-cartilage. Section of intervertebral disk or interartic-
ular meniscus, hardened in alcohol, and stained with picrocar-
mine. Nucleated protoplasts scattered in a matrix of fibrous
tissue, which may present a concentric arrangement round the
cells. Examine a fresh bit teased in serum ; add acetic acid,
the fibres swell and become indistinct.

Elastic cartilage. Examine section of lobe of ear or
epiglottis, hardened in alcohol or picric acid, and stained with
picrocarmine. Cells are large, often fall out of the spaces in the
preparation : the matrix consists of interlacing elastic fibres.

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In epiglottis, part of the matrix is hyaline, and this variety may
be regarded as hyaline cartilage permeated by elastic fibres.
Examine fresh section in serum ; add acetic acid, the fibrils are
unaffected.

Bone. Examine good transverse sections of fibula of child or of
small animal. With low power, observe medullary canal, sur-
rounded by compact bone tissue, which presents a number of
small, dark, circular spots — the Haversian canals — and little dark,
oat-shaped bodies, the lacunae, arranged concentrically around
them. Note how the Haversian canals open on the periosteal
and medullary surfaces by transverse branches. A lamellar
arrangement can be seen at inner and outer margin (circum-
ferential lamellae). With high power observe, (i) the Haversian
canal, which in fresh state contains a blood and lymph vessel ;
(2) aroi. id it in concentric rings are the lamellae (primary), often
not distinctly seen ; (3) oval spaces in the lamellae, the lacuna,
which have numerous fine prolongations, (4) the canaliculi,
passing in all directions, opening into the Haversian canals and
joining contiguous canaliculi. Each canal, with its lamellae,
lacunae and canaliculi, is termed an Haversian system, and is
more or less isolated from adjacent ones by intervening areas of
bone, which are also laminated (interstitial lamellae). A longi-
tudinal section shows the Haversian canals in their long axis ;
they have many anastomosing branches. In these specimens
all the spaces appear dark by transmitted light, as they are filled
with air and dirt which has got in during the grinding of the
section. Other important details may be ascertained in sections
of bone decalcified in chromic acid {y2 %) and nitric acid (i %)
solution, which must be changed frequently. Saturated picric
acid solution answers same purpose. Stain sections in logwood
or picrocarmine. The corpuscles in the lacunae and the con-
centric laminae are well shown. Sharpey's perforating fibres^
which pin or peg the lamellae together, can be found by stripping
off thin laminae from the decalcified bone. The perforating
fibres may be seen projecting from some of the laminae like nails
through a board. A good preparation showing the bone cor-
pucles in the lacunae mav be made from the thin parietal bone

of a small animal (mouse) stained in Beale's carmine fluid and
mounted in glycerine.

Study sections of developing bone, (a) in cartilage, from
tibia of child ; (d) in membrane — from parietal bone of embryo.

Marrow. Two kinds ; red, in most spongy bones of adult
and in all bones of infant ; yellow, in long bones of adult. Examine
a small drop squeezed from a rib with bone forceps ; put on
the top cover without any reagent, and get a uniformly thin
layer. Observe (i) colorless elements — marrow cells — of
various sizes, with large clear nuclei. Most of them are larger
than colorless blood corpuscles, others smaller— lymphoid.
Some of these elements are colorless blood cells. (2) Red cor-
puscles, usually very numerous. (3) Nucleated red corpuscles —
larger than ordinary red cells, with distinct granular nuclei,
sometimes eccentric. They are believed to be intermediate or
transitional forms (Neumann) between the colorless marrow cells
and the ordinary red corpuscles. I have traced the steps in the
process (Centralblatt f. d. med. Wissenschaften, 1878; Lancet,
Aug. 5rd, 1878). (4) Myeloplaxes, or giant cells, large proto-
plasmic masses with many nuclei. (5) Peculiar groups of red
corpuscles, enclosed in indistinct cells, the so-called cells con-
taining red blood corpuscles. The blood corpuscles undergo
atrophy and ultimately become converted into collections of
yellowish pigment, which may be seen in most specimens.
(6) In marrow which has begun to decompose, Charcot's
crystals may be seen — spindle-shaped — probably composed of
tyrosin. (7) A few fibre cells of the matrix.

Yellow marrow consists chiefly of fat cells, with a few
lymphoid cells.

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MUSCULAR TISSUE.

Two forms, the unstriped or smooth and the striated.

Unstriped. Met with in walls of gastro-intestinal canal, arteries
uterus, bronchi and skin.

Soak bit of intestine or uterus for a couple of days in dilute
bichromate of potash solution, or in a 20 % solution of nitric
acid for 24 hours, in order to loosen the adhesion of the fibres.
Tease a small bit very finely. The fibres are either fusiform,
broad at the middle and tapering at the ends, which may be
bifid, or they are flat ribbon-like. A rod-shaped nucleus exists
in each fibre. A faint longitudinal striation can be seen in some
cells. The bladder of frog or intestine of ascaris lumbricoides,
denuded of epithelium, stained in carmine and mounted in
glycerine show the fibres and nuclei very distinctly. Vide
arteries and intestines for arrangement of the fibres.

Striated. Tease bit of sartorius of frog in salt solution.

Observe cylindrical fibres with distinct transverse striation ;
slight longitudinal striation may be visible. Irrigate with
water, when in a short time a clear swelling may be seen at the
edge of the fibre ; this is the sarcolemma or fibre sheath, dis-
tended by imbibition of the water. Or it may be better shown
by teasing out fibres, keeping them parallel, and laying the
needle gently across them so as to break the muscle substance,
which then retracts, leaving the clear sarcolemma. Add dilute
acetic acid, observe the elongated nuclei, just within the sheath.
In another specimen, study the arrangement of the sarcous sub-
stance in a fibre the striae of which are very distinct. The
striation is due to the existence of broad, dim bands {the con-
tractile disks), alternating with narrow, clear bands (the inter-
stitial disks.) In each dim band or contractile disc there may
be seen in some specimens fine vertical rods (muscle rods of
Schafer). In the narrow, bright band a fine dark line divides

it transversely into two parts. This is Krause's membrane, a
transverse membranous septum passing from the sarcolemma.
By means of these septa the fibre is divided into a number of
muscie compartments, each of which consists of a dim, contrac-
tile disk, bounded on either side by a clear disk. What is known
as the cleavage of the fibre may take place in either direction ;
if longitudinally, dividing the fibre into a number of fibrils, in
each of which the alternate light and dim areas can be seen ;
if transversely, splitting the fibre into a number of disks.
Soaking muscle in i % chromic acid solution favours the
former, and hydrochloric acid, r to 50, for a week, the latter.
In the muscle fibres of the lobster it may sometimes be seen
without any preparation. If the cleavage takes place in both
directions at once little square bodies result — the sarcous
elements of Bowman. To study living muscle, examine fibres
of leg 01 Dytiscus marginalis or Hydrophilits — (the common
water beetles). Observe the waves of contraction passing along
the fibres. The same may be seen in sartorius fibres of a
recently killed frog.

Muscle of Heart. Tease finely bit of heart muscle from
person recently dead. Observe (1) the short fibres, con-
sisting of oblong or square muscle cells, which are joined
end to end by narrow band of connecting substance ; (2) the
ovoid nucleus, centric, often very pale ; (3) absence of sarco-
lemma ; (4) some of the fibres branch.

The striae are very fine, and tliere are often tiny fat droplets
or brown pigment grains in the fibres.

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NERVE TISSUE.

There are two varieties : (i) nerve fibres ; (2) nerve cells.

Nerve Fibres. (a) Mediillated or white, (d) Non-medullated
or grey.

Medullated. Exist in cerebro-spinal nerves and in white
substance of brain and spinal cord.

Tease carefully bit of sciatic nerve of frog in serum or salt
solution ; a good preparation will show nearly all details.

Each fibre consists of (i) an external elastic membrane,
the sheath of Schwann. In some fibres, hard to see, and repre-
sented only by the delicate outer line. Oval nuclei occur at
intervals beneath it ; best seen by subsequent irrigation with
picrocarmine. (2) The medulla or white substance of Schwann,
composed of a highly refractile, viscid material, called myelin.
It is situated just within the sheath of Schwann, and may be
recognized by its double contour. The myelin soon changes,
and may be seen exuding in drops from the cut ends. These
alterations are best seen in white matter of brain or spinal cord,
where the medulla has no sheath. The medulla presents inter-
ruptions in its course, the sheath of Schwann dipping in and
forming a constriction — the node of Ranvier. The portion of
the nerve between the nodes is called an interannular segment.
The medulla is penetrated by a fine network of fibres (Kiihne
and Ewald). (3) The axis cylinder, a pale, narrow band in the
centre of each fibre. It is sometimes seen projecting for a
short distance from the divided end of the nerve. It is com-
posed of deHcate fibrillae (Schultze), and a faint longitudinal
striation may indicate their presence. The axis is the essential
part of the fibre, and is continuous through the interannular
segments.

Study specimens stained with osmic acid and with silver
nitrate to show Ranvier' s nodes.

Study transverse section of sciatic, hardened in chromic

acid and spirit solution, then in alcohol and stained in logwood or
carmine. Observe the numerous nerve bundles surrounded by
the neurilemma or epineurium ; each bundle or fasciculus has a
special connective tissue ^^v^axh— perineurium, while between
the individual fibres of each bundle there is a delicate tissue, the
endoneurium. The axis cylinder alone of each fibre is stained.
Non-meduUated. Exist in sympathetic system, olfactory
nerve, and here and there as isolated fibres in cerebro-spinal
nerves. Examine fresh and osmic acid preparations. Fibres
form pale, flat filaments, with only the axis cyUnder and the
sheath of Schwann. The nuclei are numerous, and the fibres
are faintly striated.

Nerve Endings, (i) In fine plexus of fibres, representing
probably the fibrillae of axis cylinder. Study section of cornea
treated with gold chloride ; minute beaded fibrils between the
epithelial cells. (2) In modified cells, as in retina, cochlea and
olfactory membrane. (3) In peculiar terminal organs, as
{a) Tactile corpuscles (Wagner, Meissner,) in papillae of skin.
(J>) End bulbs (Krause) found in conjunctiva, lips, glans penis
and clitoris ; peculiar ovoid bodies enclosed in a connective
' tissue capsule, {c) Pacinian corpuscles. May be got in nerves
of fingers, but most readily in mesentery of cat, where they can
be easily seen as clear, oval bodies. Examine fresh, or in gly-
cerine after staining with Beale's carmine. W'th low power observe
general concentric lamination ; the nerve penetrating the centre.
With high power it can be seen that only axis cylinder enters ;
the medulla disappears. (4) In striated muscle, by granular
nucleated bodies beneath the sarcolemma — motorial end-plate.
Best seen in subcutaneous muscles of snakes. In unstriped
muscle, nerve fibres have been traced between the cells, and
according to some authors a penetration of the protoplasm
takes place.

Nerve Cells. In grey matter of brain and spinal cord, and in
ganglia of sympathetic system.

Examine (i) ganglion of sympathetic of small animal,
teased carefully in serum. (2) Bit of grey matter of anterior
comu of spinal cord of man or ox. soaked for ^8 hours in

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Mailer's fluid or H % bichromate of potash. The cells are some-
what difficult to isolate with the processes intact, and they are
perhaps better studied in sections of hardened cord. Nerve cells
vary much in size ; the largest are those of anterior cornua of
spinal cord and in the cerebellum, the smallest are in grey matter
of cerebrum. The protoplasm is granular, faintly striated, often
impregnated with pigment grains, the nucleus large, vesicular,
the nucleolus distinct. They possess a variable number of pro-
cesses, and have been divided into uni — , bi — , and multipolar
cells. It is not easy to trace the processes, but there can be
little doubt that directly or indirectly they become continuous
with nerve fibres, all of which may be said to originate in
nerve cells.

Spinal Cord. Harden bits of fresh cord of man or of cat in either
Muller's fluid, bichromate of potash solution, 2 ^, or bichro-
mate of ammonia, 3 or 4 % . Finish the hardening process with .
spirit. Stain sections in logwood, carmine or aniline blue-black.

Examine section with low power first. Observe, (i) the
anterior and posterior median fissures. (2) The pia mater, sur-
rounding the cord and sending prolongations into the fissures,
and at irregular intervals into the substance. (3) The central
grey matter, with anterior and posterior cornua and commissure
(grey), in middle of which is (4) the central canal. The grey
matter is usually the most deeply stained. (5) The white matter,
anterior, posterior and lateral columns, and anterior white com-
missure. (6) The nerve roots, which may perhaps be seen.

With high power, observe in white substance, (i) the cut
ends of the nerve fibres, consisting of the axis cylinder deeply
stained, surrounded by an unstained medulla ; they vary much
in size ; compare the large ones of anterior with those of the
posterior columns. (2) The connective tissue, enclosing the
fibres in a sort of mesh-work. This is the neuroglia which is
continuous with the septa dipping in from the pia mater. It
appears to consist of a matrix traversed by fine fibres, among
which small branched corpuscles may be seen. Some elements
of the neuroglia resist peptic digestion, and are probably
of an elastic or keratoid nature (Kiihue and Ewald). In

grey matter, observe (i) the nerve cells, collected chiefly
into certain groups, of which there are three well marked
in anterior cornu, and one in posterior horn, just behind the
grey commissure, known as Clarke's column. 'I'hose of anterior
horns are large, and present numerous processes. One of these
is unbranched, and may be traced for some distance ; it is called
the axis cylinder process, and is believed to represent the origin
of one of the nerves of the anterior root. The other processes
(called protoplasmic by Gerlach) branch and divide ; their fine
ramifications are believed to unite with those of other cells.
Strieker, however, regards them as connective tissue processes
and fibres. The cells of posterior horns are few in number and
small. The space about some of the cells is regarded as a lymph
space. (2) The nerve fibres, very minute, chiefly non-medul-
lated, passing in all directions ; they are best seen in the grey
commissure. (3) The neuroglia, which appears like a granular
matrix, but is probably reticular. It is abundant at one part of
posterior cornua — the substantia gelatinosa. The central canal
varies in size and shape. It is lined with cylindrical ciliated cells.

Cerebrum. Same modes of preparation as cord. Great care must
be taken to get vertical sections, or rather to get them exactly,
in the plane of the fibres.

The cerebrum is made up of (i) the grey cortical layer;
(2) the white medullary substance; (3) the basal ganglia.

A section of cortical grey matter usually shows five layers :
'Wit first layer, external, ^ the thickness of whole cortex, is com-
posed chiefly of neuroglia fibres, with very few cells. The
second layer consists of small, closely packed pyramidal cells
with processes. The third layer, wider than the second, con-
tains nerve elements of the same kind, but they are larger (some
very large, the so-called giant cells of the cortex), and not so
closely packed ; hence this layer looks lighter. The apices of
the cells point to the cortex, and from the base processes are
given off, one of which forms an axis cylinder. The fourth
layer, narrower than the third, consists of small, closely packed,
angular cells. In some convolutions larger cells occur. The
fifth layer, broader than the fourth, gradually shades into the

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white substance. It contains irregularly fusiform cells. This
five-laminated arrangement of the cortex is best seen in the con-
volutions of the motor area. According to Bevan Lewis, over
the greater part of the hemispheres there are six layers ; the
additional stratum, placed between the third and fourth layers,
consists of small pyramidal and angular cells. In the third layer
some of the nerve fibres may be seen to take a downward course
towards the white matter, and in the fourth and fifth strata they
form delicate bundles passing between groups of the cells. The
neuroglia appears as a homogeneous or granular matrix, but in
good preparations it can be seen to be fibrillar, and contains
small branched cells.

The white matter is composed of medullated fibres of
various sizes ; most of them much smaller than spinal or
peripheral nerve fibres. They often present varicose or bead-
like swellings.

The basal ganglia are made up of grey and white nerve
matter of essentially the same structure, but differing in
arrangement.

Cerebellum. Vertical section, prepared in same way as cerebrum.
With low power, notice the foliated or dendritic appearance.
Three layers are to be seen in the grey matter; (i) an external,
composed of a neuroglia framework, a few nerve cells, and
numerous branched processes of, (2) the cells of Purkinje,
which form the second layer. These are large ganglion cells, the
extensions of which are chiefly into the outer layer, but an axis
cylinder process is stated to pass down into the next ; (3) the
granular layer, made up of closely packed small corpuscles. The
white matter is like that of the cerebrum.

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BLOOD VESSELS.

Arteries. General structure of a medium-sized vessel is as follows :
There are three coats, (i) Tutiica intima, consisting oi {a) a.n
endothelial lining, composed of flattened cell plates ; {b) sub-
endothelial connective tissue with corpuscles, branched and
unbranched ; (c) an elastic lamina, often perforated, the fenes-
trated membrane of Henle. (2) Ttmica media, made up of
circularly arranged muscle cells, with a variable amount of white
fibrous and elastic tissues. (3) Tunica adventitia, conr^os^^oi
fibrous and elastic elements, and in large vessels muscle fibres.
In large arteries the elastic, in small arteries the muscular, tissue
predominates.

Examine (i) small artery of pia mater of human or sheep's
brain in salt solution. The straight arteries passing in at the
perforated spaces are the most suitable, as with care a long
vessel may be obtained, and the transition from medium-sized
artery to small arteriole can be traced. Add acetic acid to
develop the nuclei of muscle fibres and to determine the elastic
elements. Stain a bit in carmine and mount in glycerine.
(2) Sections of the aorta and the radial artery, hardened in
bichromate of potash or chromic acid and spirit ; stained in log-
wood. In aorta, notice in the media the alternate arrangement
of elastic laminae rnd muscle fibres. (3) A silvered prepara-
tion showing the elongated endothelial cells.

Yeins. Essentially the same structure as arteries ; the chief points
of difference are in the thinness of the coats, and the slight develop-
ment of the muscle fibres in the media and of the internal
elastic layer, which is seldom fenestrated. The adventitia is
sometimes provided with muscle elements.

Capillaries. Minute tubules, composed of endothelial cells, inter-
posed betwreen the arteries and veins. The cells are elongated,
with dentated margins, and require for their demonstration the
action of silver nitrate.

Examine (1) bit of grey matter of cerebrum, teased gently

in salt solution. The capillaries are seen as structureless tubules,
with oval nuclei. (2) A silver preparation for the endothelia.

In certain parts are ensheathed arteries and capillaries in
a membrane — lymphatic — which can be shown to be lined by
endothelium. This is what is known as the perivascular l)rmph
space. It can be seen in mesenteric vessels of frog, in those
of the nictitating membrane of same animal, and in the vessels of
the pia mater.
Circulation of Blood. Study in web of foot, tongue, mesentery
or lung of frog or tail of tadpole. The first and last objects are
the most suitable for the student. Inject into the dorsal lymph
sac of a small frog 4 or 5 drops of curare solution {}( %).
When the animal is paralysed place it on a bit of card-board,
6X2 inches, with a V-shaped notch cut out of the middle of
one end. Fix the web over this by threads tied round the toes,
and made fast in litde slits in the card-board. Wet the web, and
put on a small, thin bit of top cover. If a tadpole is used, put
it in a watch glass with a few drops of the curare solution for a
few minutes until it ceases to wriggle. Place on slide with a little
water, and put a thin cover glass on the tail.

With low power, observe the arteries breaking up into the
capillaries. The stream in these is very rapid, and it may be
noticed to be more so in the centre than near the wall (still layer).
The veins have thinner walls and the blood current is slower.
The stellate pigment cells are well seen. With high power,
study the capillary stream. The corpuscles pass in single file
and wriggle in and out through the devious paths, often bending
and displaying the elastic nature of the stroma. The colourless
corpuscles pass along less briskly, and in the veins may
frequently be seen hugging the vessel wall, as if reluctant to
move on. For studying the migration of the white blood
corpuscles the tail of the tadpole is most suitable, and the pro-
cess may be watched without difficulty. Patience, however,
is required, as it may take a couple of hours for a corpuscle
to pass through. The mesentery and tongue of frog may also be
used for this purpose ; stimulation with a tiny drop of ammonia
quickly excites the process, and the red corpuscles also pass out
(diapadcsis) at the focus of inflaiuiaatiou so excited.

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•'I I

LYMPHATIC SYSTEM.

Lymph Vessels. Capillary lymphatics are best studied in a silvered
preparation of central tendon. {Vide^. ii.) They consist of
a single layer of squamous cells, united by a cement substance,
which is stained by the silver. Observe the plexus of large and
small vessels, some with bulgings in their course. In the larger
ones a valve may be seen. The capillaries are believed to
originate in the interspaces of the tissues {serous canaliculi).

The lacteal vessels can sometimes be well seen in villi
removed from an animal killed during digestion.

Examine transverse section of thoracic duct of horse ; struc-
ture same as that of a vein.

Lymph Sacs. The subdural and subarachnoid spaces of brain and
cord, the pleura, pericardium and peritoneum are in reality
lymph sacs. The former, with their extensions around the
cerebral and spinal nerves, constitute a closed system. (Key
and Retzius.) The latter stand in open communication with the
lymph vessels by means of orifices called stoniata. These are
best seen in the silvered septum of the large lymph sac in the
abdomen of frog.

Lymph Glands. They may be regarded as nodes or collections of
adenoid tissue in the course of the lymph vessels. An afferent
branch enters, and an afferent leaves, each gland. A firm
capsule of fibrous tissue surrounds it and sends prolongations,
trabeculce, into the substance, dividing it into alveoli, which
consist of a delicate net-work, in the meshes of which are the
lymph corpuscles. In the cortical part the adenoid tissue in the
spaces between the septa forms ovid or globular bodies — the
lymph follicles ; but in the deeper or medullary part is arranged
as cord-like structures — the follicular cords. The lymph passes
through the gland in certain spaces or sinuses, lined with
endothelium, which exist between the trabecular and the gland

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Tease in salt solution a bit of fresh lymph gland. Observe
the lymph corpuscles — leucocytes — isolated and collected into
dense groups. They are a little smaller than white blood
corpuscles, and the nucleus is proportionately larger. Other
larger cells may sometimes be seen. At edges of well teased bits
the fine adenoid reticulum may perhaps be seen, and here and
there a nucleated fibre cell of the trabeculfe.

Harden gland in Miiller's fluid (ten days) or picric acid
(24 hours), and then in alcohol. Cut very tliin sections, stain in log-
wood or picrocarmine. The lymph corpuscles crowd the meshes
so closely that the details are not well seen until some of them
are removed, either by prolonged shaking oi die section in a test
tube with water, or by pencilling. The lymph sinuses can be
shown by injecting a gland with Prussian-blue solution.

The Spleen, Thymus and Thyroid glands and the Supra-renal
capsules may be considered with the lymphatic glands; they
form the so-called ductless or blood-vascular glands.

Spleen. Tease a small bit of fresh spleen pulp of man in serum or
salt solution ; or, better still, take a very small portion and let
the top-cover flatten it out as a thin layer. Observe (i) the red
blood corpuscles, very numerous. (2) Colourless elements, some
of which are white blood corpuscles ; others, a little smaller, are
the cells proper of the pulp. They vary a good deal in size ; the
nuclei are usually distinct ; smaller forms, without nuclei, may
be seen. (3) Cells containing red blood corpuscles. Very
variable ; in some specimens rare, in others abundant. All
stages can be traced between cells holding perfect corpuscles and
those enclosing yellowish brown pigment. The red corpuscles
undergo disintegration in this way. (4) Nucleated red corpuscles,
similar to those of the marrow, but not so abundant or so con-
stant as in that tissue. (5) Elongated fibre cells of the trabeculae.
From a gland in which they are distinct, pick out carefully a
Malpighian corpuscle and tease in salt solution. Observe the
lymph cells — leucocytes — of which it is composed.

For sections, harden bits of gland of cat in MuUer's fluid or
dilute chromic acid, ^^ to ^ %, and then in alcohol. Observe
(i) capsule made up of fibrous tissue, in some animals mingled

with elastic fibres and muscle elements. It sends prolongations into
the substance — the trabeculae — which constitute the framework,
the meshes of which enclose the spleen pulp. (2) The Malpighian
corpuscles, locaHzed accumulations of lymph cells in the course
of an artery. (3) The spleen pulp, which makes up the great mass
of the section, and in logwood specimens appears composed of
blue-stained cells, with red blood corpuscles. The arrangement
of the elements of the pulp is hard to make out. There is a
reticular net-work in the meshes of which the cells lie. No
capillaries exist, but the smaller arterial branches open directly
into the meshes of the pulp, and from the same the veinlets take
their origin. The arrangement is similar to the lymph sinuses in
the lymphatic glands.

The adenoid net-work is well seen in the enlarged and hard
spleen of chronic valvular disease or of leucocythemia.

Thymus. Examine section of gland of infant, hardened in Miiller's
fluid and alcohol. Observe the capsule, with its prolongations
enclosing the follicles, which consist of a reticulated adenoid
tissue with lymph corpuscles. In the central part the concen-
tric corpuscles of Hassall may be seen, curious concentrically
arranged epithelial cells, resembling the cell-nests in epithelioma.

Thyroid. Harden in same way as Thymus.

A section shows numerous gland vesicles, surrounded by
trabecular prolongations of the capsule. Each vesicle consists
of a basement membrane, lining which is a layer of epithelial
cells, somewhat columnar in form. The central space of the
vesicle or alveolus is filled with a yellowish fluid, often mixed
with the dibris of cells and blood corpuscles. The vesicles are
frequently filled with a semi-gelatinous colloid substance, and it
is the great increase of this which causes goitre.

Supra-renal Capsules. Prepare in same way as Thymus. Two
portions can be recognized, cortical and medullary. A firm
capsule invests the gland and sends sepia into the substance,
which divide the cortical part into a number of elongated com-
partments, in which the gland tissue is included. Near the
capsule these are small, like closed vesicles, but in the deeper

II:

parts they form elongated cell-cylinders. The cells differ in
appearance ; in the outer part they are coarsely granular, with
fat droplets in their interior ; in the deeper parts they often con-
tain brown pigment. The medulla consists of a matrix of con-
nective tissue, with corpuscles of irregular forms in its meshes ;
some are rounded, others branched, and some present a remark-
able resemblance to ganglion cells.

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ALIMENTARY CANAL AND ITS GLANDS.

Tooth. Prepare in same way as bone. In a longitudinal section
observe : (i) Pulp-cavity ; (2) Dentine ; (3) Enamel ; (4) Crusta
petrosa.

The dentine or ivory everywhere surrounds the pulp cavity,
and is composed of an animal matrix, impregnated with lime
salts. A series of tubes, the dentinal canals, pass through it
from the pulp cavity, running at right angles, dividing dichot
omously and anastomosing with each other. Delicate sheaths
(Neuman's) line the canals which contains the dentine fibres,
prolongations of the odontoblasts of the pulp. At the outer
margin of the dentine irregular spaces are seen — interglobular
spaces of Czermak.

The enamel surrounds the dentine above the gum line, and
consists of a series of polyhedral columns set upon, and at right
angles to, the dentine. Wavy markings or stripes cross the
enamel prisms. In cross section they look li.o a tesselated
pavement.

The crusta petrosa surrounds the dentine in the socket ; its
structure is that of bone.

The pulp. Break across a tooth of a young animal.
Examine fresh or after immersion in ^^ % solution of osmic acid
for 24 hours. It is made up of a delicate connective tissue, with
numerous blood vessels and nerve fibres ; the latter pass towards
the dentine, but it is doubtful whether they enter its tubes. Towards
the surface of the pulp there is a layer of cells — odontoblasts —
which send off numerous procciaes into the dentine tubes,
forming the dentinal fibres, and into the pulp, uniting with
other cells.

Tongue. Harden bit of organ of man or of cat in chromic acid and
spirit solution for ten days.

Mucous membrane is covered with squamous cells — best
seen in a scraping of the surface — and presents three varieties of

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papillae— the filiform, fungiform and circumvalate, together with
numerous mucous glands. Smaller papillae, similar to those of
the skin, exist all over the membrane and in the larger papillae.
In the epithelial coating of the fungiform and circumvalate
papillae, ovoid, flask-shaped bodies occur, the so-called taste-
goblets ; these are curious structures, composed of modified
epithelial cells, which are believed by many to be connected
in some way with the nerves. At base of organ, about the
circumvalate papillae, are numerous elevated bodies, consisting
of aggregations of lymphoid or adenoid tissue.

The muscle fibres of the tongue are striated, and often
branch. The section through cat's tongue makes a beautiful
preparation, from the numerous muscle bundles running in
different directions. Good prepartions, showing papillae with
nerves, and the branching of the muscle fibres can be obtained
from the tongue of the frog— preferably the tree frog — stained in
Beale's carmine and mounted in glycerine.

Salivary Glands. Two classes. (Heidenhain, Hermann's Hand-
buch, Bd. v.) (i) The true salivary glands, which furnish a
thin, fluid secretion, usually amylolytic. To this belong the
parotid of man and most mammals and the submaxillary gland
of the rabbit. (2) Mucous glands, which secrete a tenaceous
fluid, rich in mucin ; to this class belong the submaxillary and
sublingual. The submaxillary gland of man is of mixed
character — mucosalivary. Tease fresh specimens in serum.
Sections may be made after hardening in absolute alcohol or the
chromic acid and spirit solution. They are compound acinous
or racemose glands, lobulated, and intersected with connective
tissue septa. The ducts ramify through the lobules, and the
acini are grouped about their terminations. Each acinus con-
sists of a basement membrane (tunica propria), composed of
branched and flattened cells, within which are placed the true
secreting cells. These vary in appearance in the different
glands, and in states of rest and activity. In the true salivary,
they are round or polygonal, with dark granules and angular
nuclei. In the mucous glands two kinds of cells are dis-
tinguished j large, clear epithelial cells, nearly filling the lumen

Hi'

of the acinus and with a small nucleus close to the basement
membrane; and very granular cells, dispersed at intervals
between the mucous cells and the membrana propria ; they are
of an irregular, half-moon shape, and are known as the semi-
lunes of Gianuzzi. The gland ducts are at first small and have a
flattened epithelium ; in the larger branches the cells are
columnar. The termination of nerves in the cells of the glands,
as described by Pfliiger, has not been confirmed.

Tonsils. Harden in chromic acid and spirit for two weeks.

Each tonsil consists of from lo to i8 nodular masses of lym-
phoid tissue, very like a Peyer's gland. On the surface are small
crypts or slit-like depressions, and it is about these that the little
glands are arranged. The crypts are often filled with epithelial
i/3ris, particularly in slight inflammatory conditions, when the
lymph follicles enlarge and discharge a greyish-yellow material.
Squamous cells cover the surface of the gland.

CEsoPHAGUs. Distend a portion of gullet with chromic acid and
spirit solution. Suspend in the same. In this way the folds are
obliterated. Finish the hardening in alcohol.

Sections show (i) mucosa, composed of stratified squamous
cells. (2) In its deeper part the muscularis mucosae, consisting
of longitudinal unstriped cells. (3) Sub-mucosa, of areolar tissue,
with numerous mucous glands, the ducts of which may be traced
through the epithelium. (4) The muscular coat, consisting of
imstriped fibres arranged in an outer longitudinal and an inner
circular layer. In the upper part the muscularis is made up of
striated fibres. The nerve supply is abundant, and in the
striped fibres the motorial end-plates are very numerous.
(Ranvier).

Stomach. Harden bits from pyloric end and fundus, either at once
in absolute alcohol or after a preliminary immersion in the
chromic acid and spirit solution. Stain in logwood.

Section, examined with low power, shows (i) the mucosa,
tubular glands set side by side. (2) The muscularis mucosae, a thin
layer of unstriped muscle fibres, placed at the bases of the tubules
and sending up fibres between thorn, (3) The sub-mucosa, com-

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posed of connective tissue, and containing the blood vessels and
nerves. (4 ) The muscular coat, made up of two layers, longitudinal
and circular, of unstriped fibres ; in some places a third layer can
be seen. (5) The serous or peritoneal coating. With high power
examine mucosa, which presents (t) the surface epithelium,
cylindrical in form, narrow basal border, protoplasm clear in
outer, granular in inner, part. They are mucus-forming cells, and
often present clear dilatations or appear open at the end —cup or
chalice cells. This probably represents their active condition.
These cells show well in the sections, but it is better to study
them in fresh state, teased in serum. (2) The peptic glands,
which exist over the entire mucosa except in the pyloric region.
Each consists of a simple tubular gland, with basement mem-
brane and cells. The columnar epithelium of the surface
extends for about one-fourth of the length of the tube ; this is
called by some the duct, and it is separated from the lower part
by a narrow portion, the neck. Two sorts of cells line the
gland proper, one finely granular, cubical or polyhedral in form,
and occupying a more central position — the central cells or
principal cells of Heidenhain ; the other larger, coarsely granu-
lar, irregularly placed, more external, and frequently form-
ing irregular bulgings on the side of the gland; these are
called the parietal or peptic cells. The central cells are the
most numerous. The parietal cells arc small in the fasting
state, and increase in size during digestion. Heidenhain
adduces evidence to show that the pariet^'. cells secrete the acid,
and the central cells the pepsine j The pyloric or mucous
glands are larger, longer, often branched at the end, and are
lined throughout with columnar epithelium. In the deeper parts
the cells are more cubical, and resemble somewhat the central
cells of the peptic glands. They secrete mucus, and probably
also pepsine, as this substance can be obtained from the pyloric
mucosa.

liOcalized collections of adenoid tissue, lymphoid follicles,
sometimes occur in the mucosa. I have seen them in children
as distinct as the solitary glands of intestine.

Small Intestine. Prepare in same way as stomach. Study trans-

verse section Oi heum, ijrst witu low powsi

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ment of coats similar to stomach, serous ; muscular, two layers,
inner circular and outer longitudinal ; submucous and mucous!
With high power study the mucosa, which presents the following
parts for examination :—(i) The sur/ace epithelium, columnar,
with numerous goblet cells. The free border of each cell pre-
sents a distinct band or seam, which is striated. Whether these
striae represent pores, or rods, or extensions of the fibrils of the
cell protoplasm (Klein), is not yet settled. When /// situ, and
looked at from above, the cells are seen to be polyhedral, and
the ends, united by a cement substance, form a beautiful pave-
ment mosaic. Keep a kitten without food for five or six hours,
then give it milk, and two hours after examine teased bit of the
upper layer of mucosa in serum. The epithelial cells are seen
to be loaded with fat globules. These cells are the immediate
agents in the absorption of fat. Watney states that the fatty par-
ticles pass through the cement substance. (2) Lieberkiihn's glands,
simple tubular structures, which occur throughout entire mucosa
of both small and large bowel. Each consists of a structureless
niembrana i)ropria, on the inner surface of which are columnar
epithelial cells, some of which are of the goblet variety. At
the bases and between the tubules there is a delicate adenoid
tissue. (3) Villi, minute conical projections of the mucosa, com-
posed of {a) cap or coating of cylindrical cells ; {b) a matrix of
connective tissue ; {c) a rich plexus of capillaries just beneath
the epithelium ; {d) a few unstriped muscle fibres, which pass
up from the muscularis mucosae ; (<?) a central lacteal vessel,
which probably originates in the lymph spaces of the connective
tissue stroma. (4) Peyer's glands, consisting of solitary or
lenticular follicles, and agminated or patches of Peyer, which
only occur in the lower part of jejunum and ileum. A " patch"
is meftly an aggregation of the solitary glands. They are
spheroidal, or pear-shaped, and exist in the mucosa and sub-
mucosa ; they often project on the surface, and are then only
covered with the epithelium. Each is made up of a delicate
fibrous sheath, enclosing lymph cells in an adenoid reticulum.
They are in reality minute lymph glands.

Brunner's glands, seen in section of first part of duodenum,
resemble somewhat the ovloric elands of the stomach, but are

a 11

larger, and lie in the sub-mucosa. They are compound tubular
structures, and the diverticula — lined with columnar cells — dis-
charge by a common duct.

The muscu/atis mutosce resembles that of stomach.

In the sub-mucosa, besides the connective tissue and blood-
vessels, there may be seen groups of ganglion cells, the nerve
corpuscles of Meissner's plexus.

Laroe Intestine. Prepare as stotnach. Its structure is similar to
that of small bowel, except that it has no villi or patches of
Peyer ; the longitudinal muscle coat is collected into three bands,
and the serous coat contains in places collections of adipose
tissue (appendices epiploicai). The solitary follicles are nume-
rous ; the crypts of Lieberkiihn contain a larger number of goblet
cells, and are probably only mucous glands.

Blood-vessels of stomach and intestines. Examine injected
specimens. Observe the rich plexus of capillaries in the villi,
and in an opaque preparation the dense net-work about the
orifices of the peptic glands and of Lieberkiihn's crypts.

Nerves. A double plexus can he demonstrated by means
of gold chloride. Auerbach's exists between the circular and
longitudinal muscle coats, and forms a beautiful wide-meshed
plexus, in the nodal points of which are numerous ganglion cells.
A similar network, plextis myentcricus of Meissner, exists in the
sub-mucosa.

Pancreas. Harden in absolute alcohol, and stain in carmine.

It is a compound tubular gland, made up of lobules,
united by connective tissue ; each lobule is composed of a
number of tubular alveoli, arranged around a terminal duct,
the epithelium of which is flattened, while that of the larger col-
lecting ducts is cylindrical. The alveoli are lined with columnar
or blunt-pointed cells, placed on a basement membrane, and
arranged round a very narrow lumen. The external part of the
cell-protoplasm, next the membrana propria, is clear, and stains
deeply ; the internal portion is darkly granular. The appearance
of the cells changes remarkably in different states of the gland,
i.e., when active during digestion, and when quiescent in fasting.
In the latter state the granular zone occupies almost the entire

■-.-^ ilx

cell, and at this time the gland is rich in ferments. During
digestion the granular part becomes much less, and the cell
smaller. Heidenhain thinks that the granular matter represents
the zymogen or mother ferment of the Trypsin, the proteolytic
ferment of the secretion. Fine passages between the cells have
been described (Langerhans), but their significance is doubtful.

Liver. Harden bits of liver of pig and of man in Miiller's Huid (two
weeks), and then in alcohol.

The liver is made up of small lobules or acini of secreting
cells, together with connective tissue, blood and bile vessels.

The acini are irregular polyhedral masses, about 4 x i mm.,
placed on small branches of the hepatic veins as sessile berries
are on their stalks. 'I'hey are best seen in the liver of the pig,
as in that animal the lobules are invested by a distinct fibrous
sheath, whereas in man the acini are not thus isolated. Observe
with low power in the section how the liver cells are arranged in
columns or cords passing radially from the central vein of the
acinus ; the vessels of the lobules run between the spaces.
Tease a bit of fresh liver in salt solution ; the cells are large,
13-20/'., irregularly polyhedral ; protoplasm soft, granular, with
one or two distinct nuclei, and frequently fat drops or yellow
pijnnent granules. Twelve or fourteen hours after a heavy meal
the cells contain glistening flakes or clumps of glycogen, which
stain dark brown with iodine (Heidenhain).

The connective tissue forms the capsule and sends a pro-
longation into the organ at the hilus, the sheath of Glisson,
which encloses the artery, portal vein and duct. In the human
liver the amount of connective tissue between the lobules is very
slight. In the disease called cirrhosis it is greatly increased.
Compare sections of normal and cirrhotic human liver. A deli
cate fibrous tissue surrounds the central vein, and a few fibre
cells exist between the columns.

The blood vessels must be studied in injected specimens.

The portal vein subdivides, and its terminal branches
ramify between the lobules, interlobular veins. From these
vessels a rich plexus of capillaries arises, which penetrates the
lobule, pa.Hsing between the liver cells. In the centre of the

i I

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acinus the capillaries unite to form a vessel, intralobular or
central vein, which runs in the axis of the lobule and opens into
one of the sublobular veins, and the union of these forms the larger
branches of the hepatic veins.

The branches of the hepatic artery ramify in the capsule
and in Glisson's sheath ; its capillaries supply nutriment to the
vessels, ducts and connective tissue, and end in venules which
discharge into the intralobular veins.

Bile vessels can be demonstrated by injection through
hepatic duct, or by injecting indigo-carmine into the veins, when
it is eliminated through the bile ducts, which are in this way
injected. A successful preparation shows the lobules pervaded
with a small meshed net-work of delicate tubules— the bile
capillaries. They are very much smaller than the blood capil-
laries, measuring only i to 2 ^., and are never in contact with
them, but run between the surfaces of the liver cells. They
appear to possess fine structureless walls. At the periphery of
the lobule the capillaries join the interlobular ducts, »vhich unite
to form the larger bile vessels, which possess a distinct mucosa,
with cylindrical epithelium, numerous mucous glands, a wall of
connective tissue, and, in the larger ducts, unstriped muscle

fibres.

A transverse section of wall of gall-bladder shows the same
elements as the larger ducts. The mucosa presents numerous
cross ridges.

The lymphatics of the liver follow the course of the portal
vein, and entering the lobules encircle the capillaries.

The nerves can be followed to the interlobular areas, and
some observers have traced them into the lobules, but their mode
of termination is doubtful.

.1 a

ill

RESPIRATORY SYSTEM.

I vj;

With a syringe or large pipette distend lungs of cat or lobe of human
lung with f4 % chromic acid solution ; tie the trachea, and sus-
pend in large quantity of same fluid ; change after two days for
a ^ % solution, or the chromic acid and spirit solution ; and
in 8 or 10 days cut into small pieces and complete the harden-
ing in alcohol.

Trachea. In transverse section, observe (i) series of incomplete
cartilaginous rings imbedded in a fibrous layer which completes
the lube behind, and in this region is strengthened by smooth
muscle fibres. (2) Sub-mucous or glandular layer composed of
areolar tissue, in which many mucous glands are imbedded, and
collections of adipose tissue. Immediately beneath the mucous
coat there is a layer of elastic fibres, longitudinally disposed,
often, in the human trachea, collected into bundles, and showing
clearly to the naked eye. (3) The mucous membrane, composed
of a basement membrane, very distinct in man, upon which are
several layers of epithelium, the lower cells small, oval or
rounded in shape, the most internal columnar and ciliated with
interspersed goblet cells.

A section of a bronchus shows essentially the same struc-
ture, but immediately below the elastic fibres is a continuous
ring of unstriped muscle cells, which form a conspicuous and
important hyer in the bronchi.

Lung. Prior to imbedding and cutting, soak the bit of lung in the
gum or hot wax, in order to fill the air spaces ; otherwise it is
difficult to get thin sections.

The lung is composed of a series of lobules ; the peripheral
ones can be seen mapped out on the surface as irregular poly-
gonal spaces, separated by the interlobular connective tissue
septa. With each lobule a terminal bronchus or bronchiole
stands in relation, forming a narrow tube '20 to '30 mm. in
diameter, from which the cartilage rings have disappeared, but

\ HI

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which still retains the muscular and elastic elements, with a layer
of low, cubical, ciliated cells. Within the lobule the bronchiole
opens into two or three tubular passages or canals, the alveolar
passages, which have lateral and terminal extensions, the infun-
dibula. The walls of the alveolar passages and infundibula are
not defined and membranous, as in the bronchiole, but are
uniformly beset with the air cells or vesicles, which open into
them by wide orifices, and which form rounded or hemispherical
sacculi, from i to 4 mm. in diameter. The walls of the alveolar
canal, infundibula and air cells are covered with a squamous
epithelium placed upon a basement membrane. Numerous
elastic fibres exist in the walls, surrounding the orifices of
the air cells, and extending over them as a branching net-
work. Muscle fibres are also present in variable numbers,
and are increased in certain diseased states. The alveoli are
bound together by a deUcate connective tissue, in which round and
stellate connective tissue corpuscles can be seen. They frequently
contain carbon grains, and I have found them in large numbers in
specimens of miner's lung (anthracosis). Most of the above
details can be followed in good sections of cat's lung. To see
the mode of termination of a bronchiole it is, of course, necessary
to find one cut in a longitudinal direction. Immediately beneath
the epithelial elements of the air cells there is a dense plexus of
capillary blood-vessels, derived from the branches of the pulmon-
ary artery. So close is the network that the interspaces are
narrower than the vessels. In the membrane between adjoining
air cells there is only a single plexus. The capillaries of the
bronchial arteries are distributed upon the bronchi, the blood-
vessels, the connective tissue and pleura, and discharge into the
bronchial veins, in some places uniting with the radicals of the
pulmonary veins. The lymphatics form three sets (Klein), peri-
bronchial, perivascular and sub-pleural, all of which empty into
the bronchial lymph glands. Dr. Klein describes pseudostotnata
in the alveolar walls, small, round spaces between the epithelial
cells, and in connection with the lymph lacunae.

Tease a bit of fresh human lung in serum ; observe care- •
fully the elastic fibres, their size, the curved course, and the
joining of bundles from contiguous air cells. Boil a bit of lung

in a test tube with io% caustic potash solution ; examine a
teased portion for the elastic elements ; note them particularly,
as in the sputa of phthisis, and other lung affections elastic
tissue is sometimes met with, and its presence affords important
information.

ii II

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11 i m

SKIN AND APPENDAGES.

Skin. Harden in chromic acid and spirit mixture, changing every
second day for a week, and then transfer to alcohol ; or in osmic
acid, }(%, for 24 hours, and then in alcohol. It is well to take
bits from different regions, finger tips, scalp, ala nasi and scrotum.

In a vertical section observe two layers, the epidermis or
external skin and the corium or true skin, beneath which there
is the sub-cutaneous areolar and fatty tissue. Epidermis is
placed upon the corium, and consists essentially of two layers :
(i) the rete mucosum or Malpighii, next the corium, composed
of strata of cells, the lowest columnar, the middle cubical, and
the upper ones somewhat flattened. The cells are large, proto-
plasm granular, nuclei distinct, and the margins present
filaments or prickles, which interlock the cells together (rib
or prickle cells of Schultze). The cells of this layer contain
the pigment grains upon which the color of individuals depends.
(2) The cuticle, horny or corneous layer, consisting of a series of
superimposed scale-like cells, which, on section, resemble
sinuous fibres, but on maceration in caustic potash, 10%, can
be isolated as flattened cells— the so-called epidermic scales.
These are best seen by scraping the skin with a knife, and
examining the " scurf" so obtained in salt solution, A granular
layer, which usually stains deeply, and a clear layer— stratum
lucidium — may be seen in the deeper part of the cuticle.-

The corium forms a dense layer of areolar tissue, arranged
in interlacing bundles, among which are elastic fibres, con-
nective tissue cells, fixed and amceboid, and, in some regions,
ihuscle fibres. A thin membrane invests its surface. It presents
numerous conical projections, the papillae, which are ensheathed
by the rete mucosum, and contain blood vessels or nerves.
They are best seen in section of skin of fijiger-tip, being most
abundant where tactile sensation is most acute. In the lower
part, and in the sub-cutaneous tissue, are sebaceous and sweat
glands, with hair follicles.

A sebaceous gland consists of a group of acini, arranged
round a short, wide duct, which usually opens into or in connec-
tion with a hair follicle. The cells are cubical or spheroidal,
and are usually loaded with fat droplets. A little parasite,
Acarus or Demodex fol/iculorum, may sometimes be seen in the
sebum.

A sweat or sudoriparous gland is a narrow tube, the end of
which, placed in the sub-cutaneous tissue, presents a tuft or coil,
the gland proper, which is invested by a loose connective tissue.
The secreting cells are cuboidal, and are placed upon a distinct
basement membrane. The duct passes vertically through the
corium, and in the epidermis pursues a spiral course, opening
on the surface by a funnel-shaped orifice.

The blood-vessels of the skin are very abundant, forming a
lower and upper plexus in the corium ; from the latter, branches
pass into many of the papillae.

The nerves of the skin terminate in the tactile corpuscles of
the papillae, in Pacinian corpuscles, and in the rete mucosum by
a fine inter-epithelial plexus.

Hair. Examine a hair of the head ; observe the cuticle, consisting
of a series of imbricated scales ; the cortex, densely packed
elongated scales, with different-colored pigment grains inter-
spersed among them ; the medulla or pith, not always present,
composed of granular polyhedral cells, which sometimes have
air bubbles between them. Hairs of the head are cylinders ;
those of the beard flattened, and with an oval section.

The hair is placed in a follicle or involution of the corium,
and has an epidermic sheath, corresponding to the epidermis ;
below it is attached to and grows from the papilla, a conical
projection, composed of connective tissue, numerous rounded
cells, blood-vessels and non-meduUated nerves. Muscle fibres —
erector pili — are connected with some follicles.

Examine hairs of cat, dog, rat, mouse, horse and ox.

Nails. Correspond in structure to the skin, and are only modifica-
tions of it. The matrix or bed— corium— presents numerous
highly vascular papillae, upon and between which is the rete

I II

mucosum, the cells of which by a gradual process of flattening,
become converted into the homy scales, composing the nail
proper. These can be isolated after maceration of the nail in
30% caustic potash solution.

'.I

GENITO-URINARY SYSTEM.

Kidney. Harden bits from organ of man and of cat in the chromic
acid and spirit solution, or Miiller's fluid (three weeks), and then
in alcohol. Neutral chromate of ammonium, 5 % , for two days,
then in alcohol to show the rod-epithelium of Heidenhain

For the epithelium and Henle's loops tease bits of kidney
of infant in serum, either fresh or after steeping in Miiller's fluid.

The organ consists of a series of complicated tubes — tubuli
uriniferi — and a rich supply of blood vessels.

Study first a median section of afresh kidney. Observe (i)
the ccrtical and (2) the medullary or pyramidal portions, the
latter being striated and forming cones, which terminate as the
papillae. The cortex is not uniform, but presents definite pro-
longations from the medulla in the form of bundles of tubules
— the medullary rays— and in the interspaces between these a
double row of small vascular bodies — the Malpighian tufts.

A iiriniferous tubule begins in the cortex, and after a series
of complicated windings opens at the apex of a papilla. It con-
sists of ( I ) a dilated, flask-shaped extremity — Bowman's capsule —
a structureless membrane, lined with flattened epithelium. (2)
The convoluted tube, joined to the capsule by a narrow neck.
This portion is wide, and pursues an exceedingly tortuous
course. It is lined with polyhedral cells, the outer halves of
which present peculiar rod-like structures, resting against the
basement membrane — the so-called rods of Heidenhain. (3)
The tube diminishes rapidly in size, leaves the cortex, and
enters the medulla to a variable depth ; then, gradually widen-
ing, returns to the cortex, forming the loop of Henle. The
descending limb is very narrow, and is lined with flattened cells,
the nuclei of which project and give a sinuous appearance to the
lumen. The ascending limb is much wider, and its epithelium
is essentially the same as in the convoluted tube. (4) The tube
again becomes convoluted, intercalated portion., and eventually
terminates in (5) a collecting tubule of medullary ray, which,

111

small at first, passes into the pyramid, gets larger, and uniting
with others, forms one of the large (6) discharging tubes. Ihe
epithelium of these varies somewhat in different regions ; in the
collecting tubules it approaches the cylindrical form ; m the dis-
charging tubes the cells are typical cyhnders

To see the general arrangement of the convoluted and
straight tubes, study large sections of cat's kidney under low
power Cross sections of the straight tubes show very well the
different size of the tubules and similar sections of the cortex
show the medullary rays in bundles among the convoluted
tubes To isolate the tubes, soak a bit, the size of a pea, in
pure hydrochloric acid for twelve hours, and then in water for a
day; tease in osmic acid, i %, and mount in Farrant's solution

^"^ ^^ood-vesse/s. A peculiar and beautiful arrangement of the
blood-vessels exists, the det^^ils of which can be followed in well-
iniected specimens. The medium-sized arteries run on the
surface of the pyramids, and send branches up mto the cortex
and down into the medulla. The former pass between the
medullary rays and give off little branches, each of which pene-
trates a capsule-z'a. aferens-~and breaks up into a coil of
capillaries, the Malpighian tuft or glomerulus, from which a
small vein arises, emerges from the capsule-z;^^ efferens--ntBX
the afferent artery, and then forms a dense network of capillaries
about the convoluted tubes, from which a vein arises. The
glomerulus has a delicate coating of flat epithelial cells. From
the arteries, at the bases of pyramids, other branches penetrate
the mtm\2^-arteriolcB rectce-^nd break up into capillaries

about the straight tubules. • , , •

The connective tissue of the kidney is scanty, particularly in
the cortex. In teased sections spindle-shaped corpuscles are not
uncommon, and in cross-sections of the pyramids a nucleated
connective tissue is seen separating the tubules. A delicate
layer, strongly developed in some cases of disease, exists about
the Malpighian capsules.
Ureter and Bladder. Distend separately with chromic acid and
spirit solution ; place in same mixture for several days, and then

111 CLl^^^lt^^^*

t>-i, rl

Ureter. A section shows an external fibrous sheath ; two
muscle layers, an internal longitudinal and an external circular ;
a mucous coat, with epithelium same as bladder.

Bladder has essentially the same structure, but a serous
membrane covers it in part, and the muscular coat consists of
numerous bundles of interlacing fibres, described as occurring in
three layers — circular, longitudinal and oblique. The epithelium
is important, and can be studied in sections or in fresh teased
specimens. That of the ureter and pelvis of kidney presents the
same appearance ; it is of the variety known as transitional.
(See Epithelium).

Prostate. Made up of saccular acini, lined with cylindrical epithe-
lium and surrounded with a large amount of connective tissue
and muscle fibres.

Testis. Organ of dog, rabbit or pig, sliced in several directions, and
hardened in chromic acid and spirit solution, and after a week in
alcohol.

To isolate the tubes, macerate, at about 30° C, in hydro-
chloric acid (one of acid to two of water) for 48 hours, and sepa-
rate carefully in water.

Section of gland shows a fibrous capsule, tunica albuginea,
which sends septa into the substance, dividing it into a number
of lobules, filled with the seminal tubes, which divide and sub-
divide, and are much folded. Each tube consists of (i) a
membrana propria, composed of flattened epitheloid cells. (2)
The seminal cells, arranged in several layers, the outermost
rounded and faintly granular, the inner polyhedral, granular and
present numerous developing spermatozoa — hence the term
spermatoblasts is given to them. The mode of their development
in the cells is still disputed, but it appears that the nuclei divide
into a number of portions, each of which forms a head, while
the tail results from the transformation of the granular proto-
plasm of the cell (Fleming. Archiv f. Micros. Anat., Bd. XVIII.)
In the tubes they can be seen in groups, heads together and the
tails forming brush-like extensions towards the lumen.

Spermatozoa. Obtain from vesiculce seminales or testicle of
man, or, in living state, by squeezing penis of dog, and at same

time placing slide against the glans. Can be mounted dry, or
in glycerine to which a few drops of alcohol have been added.

Observe ( i ) head, which is pear-shaped, flattened, and pre-
sents an anterior dark and a posterior lighter segment. (2) The
tail, consisting of an anterior thicker portion—in spermatozoa of
some animals very distinct, and known as the middle part or
body— and a long tapering thread, the tail proper. A delicate
vibratile filament, often spirally arranged, exists in the tail or is
attached to it by a thin membrane, and it is by means of this
that the active movements are effected. (Eimer, Jensen,
Gibbes.)

Ovary. Harden ovary of cat or dog in chromic acid and spirit
solution. If human ovary, make several cuts into it. It is best
to stain the sections in carmine. They must be handled very
carefully, as the ova are liable to fall out of the larger follicles.

The organ is made up of (i) an external epithelial coating
of low columnar cells. (2) The parenchyma, composed of dense
connective tissue, with some elastic and muscular elements.
(3) The Graafian follicles, situated in the outer or cortical part
of the stroma. They vary in size from a pin's head to a pea, and
in a large one the following parts can be seen : (a) fibrous coat-
ing, continuous with the stroma of the gland ; {b) a basement
membrane, lined by {c) several layers of granular cells— the
membrana granulosa. The ovum is usually attached to one
side of the follicle, and is surrounded by {d) the discus pro-
ligerous, composed of irregular granular cells, which completely
invest the ovum ; {e) the liquor folliculi, an albuminous fluid,
which fills the follicle. The ovum is a spherical body, consisting
of the vitellus or yelk, with a vesicular nucleus, the germinal
vesicle, which contains a nucleolus, the germinal spot. Surround-
ing the vitellus is the zona pellucida, a finely striated cell wall,
and on the outside of it a layer of cells— the epithelium of the

germ.

In the sections numerous small unripe follicles can be seen
near the surface, containing distinct ova but no follicular fluid.

Corpus luteum. After the rupture of the mature follicle and
the discharge of the ovum, certain changes go on in the sac,

which result in the formation of a stnicture known as the corpus
luteum. A section of a fully developed one shows (i) an exter-
nal convoluted wall of a yellow color, composed of irregular
cells, with yellow pigment grains ; sometimes large multinuclear
cells are seen. The precise mode of development of this
distinctive layer is still in dispute, whether from granulosa
remnants, cells of the stroma, or migrated white blood
corpuscles {2) A central mass, which results from the trans-
formation of the blood effused after the rupture, and which
consists of a rascular tissue (organized clot), with a few cells.
Color is variable, often light reddish brown in centre and a
pale, peripheral part. Haemaioidiii grains and crystals are
numerous, and are easily obtained from ovary of cow. Occasion-
ally a central cavity, containing serum, is found. The corpus
luteum which forms after menstruation reaches its full develop-
ment in about three weeks — corpus luteum of menstruation ; when
impregnation takes place the corpus luteum grows much larger,
reaches its full size in about three vc\oxi\.\\'6— corpus luteum of
pregnancy. Retrograde changes then go on, and, in the former
case in a few weeks, in the latter in four or five months, reduce
the corpus to the condition of a white cicatrix, often with a
dark centre. Frequently in sections deeply placed follicles are
seen, with rigid, white, puckered walls. These are \\\q false cor-
pora lutea (Dalton), which result from a saccular degeneration of
the follicles, and the term should not be, as it sometimes is, applied
to the corpus luteum of menstruation.

Fallopian Tube. Prepare in same way as ovary. In tranverse
section, (i) serous coat; (2) muscular, double layer, internal
circular, the thicker of the two ; (3) the mucous membrane, in
longitudinal folds ; epithelium is cylindrical and ciliated , direction
of the current is towards the uterus.

Uterus. Prepare in same way as ovary, or in case of small ani-
mals the solution may be injected into it, and the vagina tied.
The organ should be obtained as fresh as possible.

It presents for study (i) serous coat. (2) A very thick mus-
culature, disposed in several layers, the fibres being of the un-
striped variety. (3) The mucosa, a thin lining, closely united to the

/- r

muscular coat, which presents (a) a uniform covering of cylindrical
ciliated cells, (l>) a stroma of spindle-shaped cells, and (<•) tubu-
lar glands, often tortuous or branched, and lined throughout with
columnar ciliated epithelium.

Study with great care teased preparation?, of fresh mucosa
in serum ; sketch and observe the various sorts of cells. Isolate,
by teasing, the muscle cells (a) of unimpregnated (*) of preg-
nant uterus. This is greatly facilitated by soaking a portion of
the tissue in ,'o % bichrom. solution. The cells are fusiform or
flattened, in the unimpregnated organ about .045 mm. m
length, nucleus single, rod-shaped. The fibres are held
together by a cement substance of connective tissue, m which
small cells are to be seen. In the organ at term, or shortly after
delivery, the muscle cells are greatly enlarged, measure .660 mm.
in length, and look altogether broader and bigger.

Vagina. Study epithelium ; large squamous cells, often folded. In
sections muscular and fibrous layers can be seen outside of the
mucosa.

Mammary Gland. Harden in chromic and spirit solution, then in
alcohol, and stain with logwood.

It consists of a series of acinous or racemose glands, united
by a connective tissue framework, which separates the lobules
and encloses the vessels and ducts. Each lobule consists of a
group of acini, arranged round a terminal duct. The acini or
gland vesicles are rounded or polyhedral in shape, and present
a basement membrane lined by short columnar cells, which, in
the functionally active gland, may be seen to contain milk
globules. It is probable that the cells give exit to the oil
globules without undergoing destruction. The gland ducts are
lined with cuboidal cells ; near the nipple the large galactophorus
ducts present saccular dilatations.

'jMs

EYE.

Cornea. Prepare in Miiller's fluid and alcohol , staki 'm
carmine or logwood. For corneal corpuscles, soak m gotrf
chloride solution, ^ %, for an hour ; then in acidulated
water, and mount in glycerine. For lymph spaces, pencil with
solid stick of silver nitrate ; mount in glycerine.

In section, observe: (i) Anterior epithelium, stratified,
many of the cells "ribbed." (2) Bowman's membrane or
anterior elastic lamina, a clear homogeneous layer. (3) The
substantia propria, made up of lamellae of fibrous tissue, sepa-
rated by an albuminous cement, in which are the lymph spaces
and corpuscles. (4) The posterior elastic lamina or l>escemet's
membrane, a structureless, transparent layer, upon which there
is placed (5) the posterior epithelium, a single layer of cuboidal
cells.

The lymph canaliculi are flattened stellate spaces, which
anastomose with each other. They contain the fixed corneal
corpuscles, which are flat cell plates, with pointed processes.
Amoeboid cells are also found in the spaces.

The delicate nerve fibres end in a sub-epithelial and an
intra-epithelial plexus (Klein).

Sclerotic. Composed of interlacing bundles of fibrous tissue,
with a few elastic fibres.

Lens. Composed of elongated fibres, forming broad, flat
bands, hexagonal on section. They can be most readily studied
in the eye of any large fish ; boil the lens for a few minutes,
strip off a few fibres, and mount in glycerine. They present
numerous serrations, which interlock the contiguous fibres.

Choroid. This layer consists of a connective tissue paren-
chyma, a few elastic fibres, pigment cells, and numerous blood-
vessels.

Tease bit of fresh choroid of pig's eye in serum for the
branched pigment cells.

|~ jw ww i, « ywi iw>iw ww >l y ' *

!l I

t !

Ir r

Study the relation of the parts at the comeo-sderotic junc-
tion in a good horizontal section. Notice: (i) The transition
of the cornea into the sclera ; a small aperture at the junction,
the canal of Schlemm. (2) The choroid, lining the sclera
behind and' presenting folds, the ciliary processes ; in front it is
continuous with the iris. (3) The ciliary muscle, consisting of
a radial and a circular set of fibres, attached in front at the
corneo-sclerotic junction, and passing back to be mserted into
the choroid and its ciliary processes.

The iris resembles the choroid in structure, but has a double
set of smooth muscle fibres ; the sphincter, forming a ring near
the margin of the pupil, and the dilator, the fibres of which pass
radially towards the periphery.

Retina. Posterior half of eye of pig or fresh human eye in
MuUer's fluid for a week, and then in alcohol.

In a successful section observe following layers :—

(i.) Internal limiting membrane, next the vitreous.

(2.) Layer of nerve fibres, non-medullated.

(3.) Ganglion-cell layer, usually but one row. An axis-
cyUnder enters the inner side, and each cell sends off processes

into the next layer.

(4.) Inner molecular layer, composed of a homogeneous
substance, with numerous little spaces in it.

(5.) Inner nuclear layer, made up of oval nerve cells, with
distinct nuclei and a process from either end. There are also
some unbranched cells.

(6.) Outer molecular layer, similar to but much thinner than

the inner.

(7.) Outer nuclear layer, consisting of oval cells, which are
connected by fibres with the rods and cones.

(8.) External limiting membrane, a clear, well-defined line
at the base of the rods and cones.

• (9.) Layer of rods and cones. Rods are cylindrical, and
consist of an inner and outer part, the latter being transversely
striated. The cones are bottle-shaped, and consist of an inner cone,
and an outer cylinder, like that of a rod, but not of equal height.
(10.) Pigment layer, which receives the ends of the rods
and cones, forms a single stratum, of flattened hexagonal cells.

Layers 7 and 9 constitute the neuro-epit helium (Schwalbe),
in which the optic nerve fibres terminate.

A connective tissue framework supports these layers, chiefly
as the fibres of MuUer, which arise from the internal limiting
membrane, and pass through the whole thickness to the external
membrane. .

-'1 '

it ,

i j

EAR.

Externa/ meatus is lined by an extension of skin, which
presents numerous ceruniii»ous glands, resembling the sweat
glands in structure.

Membratia tympanL Three layers : External is a layer of
squamous epithelium ; middle, composed of fasciculi of fusiform
fibres, in several layers, with blood vessels, lymph channels and
nerves ; internal, a layer of flat epithelial cells.

Tympanum. Mucosa consists of a basement of connective
tissue, upon which is placed an epithelium, which, in places, is
columnar and ciliated, but on the roof, the membrana and on the
ossicula is squamous.

Eustachian tube. Mucosa is lined by a layer of columnar
ciliated cells.

Cochlea. Remove organs from guinea-pig, put in MuUer's
fluid for ten days, then in saturated picric acid until softened.
Transfer to weak spirit, and in twenty-four hours to strong
spirit (Scliafer).

The cochlea is a spiral tube, taking two and a-half turns
round a central axis— the modiolus. The canal is divided by a
thin partition, partly osseous, partly membranous— the lamina
spiralis, inio an upper part, the scala vestibuli, and a lower por-
tion, the scaia tympani. From the middle of the spiral lamina a
thin membrane passes to the outer wall of the scala vestibuli,
cutting off" a narrow triangle, known as the ductus cochlea.

The organ of Corti, a peculiar body in which the cochlear
nerve terminates, is placed in this duct, being situated upon
the basilar membrane— the membranous portion of the lamina
spiralis.

These three cochlear canals are lined with squamous epithe-
lium. The organ of Corti forms a complicated epithelial struc-
ture, projecting as a small arch on the floor of the ductus cochleae.

,l> .

It consists of an inner and an outer set of rods or pillars, inclined
towards each other, the heads interlocking and leaving a little
channel beneath. In connection with these rods are epithelial
cells with hair-like prolongations, four rows on the outer side of
the outer pillar, one on the inner side of the inner. Beyond
these the epithelium is cylindrical, and then cuboidal. The
nerves have been traced to the inner and outer hair cells.

Membranous semi-circular canals consist of (i) an external
connective tissue layer; (2) a middle tunica propria; (3) an
internal pavement epithelium.

In the ampulla the epithelium presents a number of colum-
nar supporting cells, between wHich are placed fusiform cells
provided with si\& cxXm— auditory hairs. These cells appear to
be in direct connection with the terminal filaments of the vesti-
bular nerve.

■'•^\

til

Ji "i1 II

NOSE.

Three regions : Vestibuluni nasi, pars respiratoria, and pars
olfactoria.

The vcstibvlum comprises the part just within the nostrils,
and surrounded by the cartilages. The membrane covering it is
an extension of the skin, which gradually merges into the
mucous layer. The epithelium is squamous.

The respiratory portion comprises the greater part of the
fossas, except the upper region. The mucosa, known as the
Schneiderian membrane, is composed of ciliated epithelium
placed upon a connective tissue stratum, which foiTns a perios-
teum for the nasal bones. In the fossae it is thick, and presents
mucous glands, with numerous blood-vessels, arranged, according
to some writers, as an erectile tissue. In the sinuses it is thinner.

The olfactory portion^ confined to the roof, upper part of
the septum and the superior turbinated bones, has a light yf^Mow-
brown color. The membrane is made up of a connective tissue
matrix, covered with two sorts of epithelium, one the olfactory
cells, elongated structures, with fine cilia on the surface, which are
connected below with terminal filaments of the olfactory nerve.
In mammals the cilia are absent. The other variety are ordinary
columnar cells. These cells are best studied in the newt or frog,
after immersion of the head, with the nostrils slit up, in Miiller's
fluid. Numerous pigment granules, and some pigment cells
exist in this part. Bowman's glands, tubular in structure, are
seen throughout the thickness of the mucosa.

INDEX.

PAOB

Acarus folliculorum ^^

Accessories — Microscopic xvi.

Achorion Schtfnlini .

Adipose tissue , , , . , i^

Adjustments yjjj

Adenoid tissue ••. • i ,

Air bubbles i

Air cells ^

Alcohol xi.

Alimentary canal ,i

Alveolar passages ^

Amoeba 2

Ammonium chromate xi.

Ampullae ce

Aniline djes xiv.

Areolar tissue i.

Arteries 2-

Arteriolae rectae 45

Auditory hairs ec

Auerbach's plexus ^5

Bacteria a

Baccillus c

Bichromate of potash xi.

Bichromate of ammonia xi.

Bile vessels 38

Bladder , 4»

Blood corpuscles — Man 6

" " — Other animals 9

" '• — Nucleated 9.17

Blood crystals q

" Counting o

Blood vessels 25

Bone 16

Bowman's capsule 45

•' membrane 51

" glands 56

" disks 19

Bronchus 39

Brownian movement ..,.,* 35

Brunner's glands

ix.

Camera lucida * * ,6

Canaliculi of bone 27

' ' Serous j^^j

Canada Balsam 25

Capillaries xiii.

Carmine fluids i ^

Cartilage ^

Cells 3

Cell multiplication

Cells with red-blood corpuscles ".'."".*.*'.'.'.'.'.'.'. 23

Central canal 23

Cerebrum 24

Cerebellum ] i^

Charcot's crystals 51

Choroid xi.

ChroUiic acid xi.

Chr. acid and spirit i

Chyle .S2

Ciliary muscle 26

Circulation 23

Clarke's column 54

Cochlea 13

Connective tissues 51

Cornea ^2

Comeo-sclerotic junction 54

Corti, organ of 48

Corpus luteum ^2

Corium i

Cotton fibres * " ' ' 5

Crenation ,1

Crusta petrosa '"" ^^^

Cutting sections 3

Cyclosis ji

Czermack's spaces

xi.

Dammar ^2

Demodex folliculorum • 31

Dentine ci

Descemet's membrane • xii.

DissocJftTing fluids ^^^^

Drawing' ^^

Ductus cochleae ,,.... i

Dust "

PAGB

Ear 54

Elastic tissue 14

Elastic fibres of lung 40

Elastic cartilage 15

Enamel 31

End bulbs 21

Endoneurium, 21

Endothelium 11

Epidermis 42

Epithelium, squamous , 11

" glandular 11

" columnar 12

" ciliated 12

" transitional 12

Erector pili 43

Eustachian tube 54

Eye 61

Eye-piece viii.

Fallopian tube 49

False corpora lutea 49

Farrant's solution xvi.

Fibrin fibrils 8

Fibrous tissue 14

Fibro-cartilage 15

Fungi 4

Genito-urinary system 45

Glomerulus 46

Gold chloride xv.

Gold size xvi.

Glycerine xvi.

Glycerine jelly xvi.

Graafian follicle 48

Granules i

Hair 43

Hardening fluids xi.

Haversian canals 15

Hsemin 10

1 Isematoidin 10

Haemoglobin 9

Hsematoxylin' xiv,

Heart, muscle fibres 19

Heidenhain's rods 45

(:(

, «»■»>*««.-■-«»»«!!';*' ;>.

PAOI

Henle'8 loop ^^ ^

Hepatic artery ^

. ^. viii.

Illumination

, , , Xll.

Imbedding mixtures

Imbedding ...'

Immersion lens

Infundibula '^

Indifferent flui Js

Intestine, small 3*

" large ^

Interlobular veins 37

Iodized serum

Iris • 52

Kidney ^^

Krause's membrane ^9

Lacunse ^

Lamina spiralis •'^^

Lens •^

Leucocyte '

Lieberkiihn's glands 35

Linen fibres *

Liver "

Logwood

Lung 39

Lymph vessels ^7

" glands ^7

" sacs ^7

Magenta '

Malpighian corpuscles ^°

tufts 46

Mammary gland •'*°

Marrow '

Meatus externus _ 54

Meissner's plexus 3°

Membrana tympani 54

Methyl-aniline ''*^-

Micrococci ^

Microcytes ,.

Microscope ^"*

Microtomes *'"•

Microsporon furfur 4

^»... I

aiiiK '

PAOl

Motorial end-plates 3i

Moulds ^

Mounting xv.

Mucoid tissue 12

Miiller's fluid xi.

Muscular tissue 18

Myeloplaques i»

Nails AX

Nerve cells 21

Nerve fibres 20

Nerve endings 21

Neuroglia ,4,22

Neurolemma 21

Neumann's sheath 7i

Objective vii.

Oil drops I

Olfactory cells c6

CEsophagus ^^

Osmic acid xii , xv.

Ovary ^8

Pacinian corpuscles 21

Pancreas ^5

Papillae, of finger 42

" of tongue ,2

Penicillium glaucum

Perineurium 21

Perivascular lymph space 26

Peyer's glands ,c

' ' patches , c

Picric acid xii.

Picro-carmine xiv.

Pigment tissue i c

Portal vein ,»

Prostate ah

Protoplasm 2

Pulp '. 31

Purkinje's cells .- 34

Ranvier, node of 20

Respiratory system ^q

Retina (-2

Rete mucosum 42

" Malpighii 34

Rods and cones C3

#imm>mlf*nm^"»it ^

Saccharomycetes

Salivary glands

Salt solution

Sarcous elements

Scala ■ di."*' -'

" lympRiU

Schivfer's rods

Schlemm's canal

Schizomycetes

Schneiderian membrane.

Schwann's sheath

Schultze's granules

Sclerotic

Sebaceous gland

Semi-circular canals

Serum

Sharpey's fibres,.

Silver nitrate

Skin

Small intestine

Softening solutions.

Spermatozoa

Spinal cord

Spirillum ■

Spleen

Staining fluids ■

Starch grains

Stomata

Stomach

Substantia gelatinosa.
Sudoriparous glands . .
Supra-renal capsules-.
Sweat glands

Tactile corpuscleR.

Taste goblets

Teasing

Testis

Thymus

Thyroid

Tongue

Tonsils

Torula

Trachea

Trichophyton tonsuraus .

PAOI

• 4

• 19

4
S6
20

8
51
43
55

xiv.

34
xii.

• 5
, 28
. xiii.

• 27

• 33

• 43
. 29

• '43

. 21

• ,P
. xi.

• 47

29
^9

32
4

39
4

PACW

... 4

... 33

... 19

• • •

... 52

... 4

... 56

. .. 20

... 8

... 51

• • • 43

• • • 55

, . . . X.
.... 16
... xiv.
. . . . 42
. . . . 34
. .. . xii.
. . . . 47
. . .. 22
.... s
. . . . 28

xiii.

.... 27

• •• • 33
.... 23
.... 43
.... 29
.... '43

.... ]2

.... xi.
.... 47

PAOR

Tubuli uriniferi 45

Tympanum 54

Ureter 47

Uteruft 49

Vacuolation 3

Vagina SO

Vegetable cell ^

Veins ^5

Vibrio S

White-blood corpuscles 7

White fibrous tissue •'* • H

Woody fibres *

Woollen fibres *

Yolk of egg ^