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THE CURIOSITIES OF THE MICROSCOPE ; 
 
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 ILLUSTRATIONS OF MINUTE PARTS OF CREATION. 
 
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PLATE. 2. 
 
 T. Sindairs 
 
OR, 
 
 THE 
 
 MICROSCOPIST; 
 
 3Jtattttfll 
 USE OF THE MICROSCOPE 
 
 FOR 
 
 PHYSICIANS, STUDENTS, 
 
 AND ALL 
 
 LOVERS OF NATURAL SCIENCE. 
 
 SECOND EDITION, IMPROVED AND ENLARGED. 
 
 WITH ILLUSTRATIONS. 
 
 BY 
 
 JOSEPH H. WITHES, M.D. 
 
 PHILADELPHIA: 
 
 LINDSAY AND BLAKISTON. 
 
 LONDON: 
 
 TRUBNER & C0. 
 1853. 
 
Entered, according to Act of Congress, in the year 1853, 
 
 BY LINDSAY AND BLAKISTON, 
 In the Clerk's Office of the District Court for the Eastern District of 1'ennsylvania. 
 
 C. SHERMAN, PRINTER. 
 
TO 
 
 PAUL BECK GODDARD, MJD., 
 
 DISTINGUISHED BY 
 
 HIS ARDENT AND SUCCESSFUL PROSECUTION 
 
 OP 
 THIS AND KINDRED STUDIES, 
 
 IS RESPECTFULLY INSCRIBED 
 BY 
 
 THE AUTHOR. 
 
 M354533 
 
PREFACE 
 
 TO THE SECOND EDITION. 
 
 THE rapid sale of the first edition of this work, both in 
 England and the United States, proves its adaptation to the 
 wants of the scientific community, and justifies the care and 
 extra expense with which this second edition has been prepared. 
 
 Although the first edition was unusually large, it is not at 
 all probable that the demand has been exhausted. But a little 
 more than a year has elapsed since its appearance, yet sufficient 
 time has been afforded for the author to make a number of 
 important additions, which increase the value of the work to 
 the student of nature. 
 
 The facts relating to microscopic science are not the result 
 of one man's labors, or of a single generation, but have been 
 gradually accumulating for many years ; yet at the present the 
 number of indefatigable observers is very considerable, and the 
 author is presumptuous enough to think that the preparation 
 of this manual has increased that number, by diminishing the 
 difficulty of the study, and pointing out the most judicious 
 methods of observation. 
 
V1H PREFACE. 
 
 For the flattering notice taken of this work by the medical 
 and scientific journals, the author is under many obligations, 
 many prominent periodicals having spoken of it in terms of the 
 highest praise. 
 
 It has formed no part of the design of this book to describe 
 the mechanical arrangements of different instrument-makers; 
 yet sufficient directions have been given to enable any one pos- 
 sessed of a microscope, of any mechanical form and arrange- 
 ment, to use it to the best advantage. , Whatever be the 
 favorite pursuit of the student, whether Botany, Zoology, 
 Anatomy, Physiology, or Pathology, the present manual gives 
 information, by means of which the microscope may be profit- 
 ably employed. In addition to this, the chapters on Minute 
 Dissection, Injection, &c., will be of interest to many. 
 
CONTENTS. 
 
 CHAPTER I. THK HISTORY AND IMPORTANCE or MICROSCOPIC IN- 
 VESTIGATION, .... .- 13 
 II. THE MICROSCOPE, .... 22 
 
 III. ADJUNCTS TO THE MICROSCOPE, . . .41 
 
 IV. How TO USE THE MICROSCOPE, . . 51 
 V. ON MOUNTING AND PRESERVING OBJECTS FOR EXA- 
 MINATION, . . . . .55 
 
 VI. ON PROCURING OBJECTS FOR THE MICROSCOPE, 67 
 
 VII. TEST OBJECTS, . . . . .110 
 
 VIII. ON DISSECTING OBJECTS FOR THE MICROSCOPE, 118 
 
 IX. THE CELL-DOCTRINE OF PHYSIOLOGY, . . 129 
 
 X. EXAMINATION OF MORBID STRUCTURES, ETC., 139 
 
 XI. ON MINUTE INJECTIONS, . . . 158 
 
 XII. EXAMINATION OF URINARY DEPOSITS, . .169 
 
 XIII. ON POLARIZED LIGHT, . . . . 188 
 
 XIV. MISCELLANEOUS HINTS TO MICROSCOPISTS, . 196 
 

THE MICEOSCOPIST. 
 
 CHAPTER I. 
 
 THE HISTORY AND IMPORTANCE OP MICROSCOPIC 
 INVESTIGATION. 
 
 FROM the earliest period of scientific research, the magnify- 
 ing properties of lenses have been used to penetrate the arcana 
 of nature, and with most striking results. A vast amount of 
 information, which could have been obtained in no other way, 
 has been added, by microscopic observation, to almost every 
 branch of natural science. 
 
 To the Christian philosopher, the microscope reveals the 
 most amazing evidence of that Creative Power and Wisdom 
 before which great and small are terms without meaning. He 
 rises from the contemplation of the minutise which it displays, 
 feeling more strongly than ever the force of those beautiful 
 words " If God so clothe the grass of the field, which to-day 
 is, and to-morrow is cast into the oven, shall he not much more 
 clothe you ? ye of little faith !" 
 
 To the geologist, it reveals the striking, yet humbling fact, 
 that the world on which we tread is but the wreck of ancient 
 
14 THE MICROSCOPIST. 
 
 organic creations. The large coal beds are the ruins of a 
 luxuriant and gigantic vegetation; and the vast limestone 
 rocks, which are so abundant on the earth's surface, are the 
 catacombs of myriads of animal tribes which are too minute 
 to be perceived by the unassisted vision. It exhibits, also, 
 that metallic ore, as the Bog Iron Ore, and immense layers of 
 earthy and rocky matter, are formed merely by the aggregation 
 of the skeletons or shields of Infusoria ; while beds of coral 
 rocks are still in the process of formation, the architects being 
 tiny marine polypi. Further, by this instrument, the nature 
 of gigantic fossil remains is often determined, and by it they 
 are assigned their true place in the classification of the 
 naturalist. 
 
 To the student of vegetable physiology, the microscope is an 
 indispensable instrument. By it he is enabled to trace the 
 first beginnings of vegetable life, and the function of the dif- 
 ferent tissues and vessels in plants. 
 
 The zoologist finds it also a necessary auxiliary. Without 
 it, not only would the structure and functions of many animals 
 remain unknown, but the existence of numerous species would 
 be undiscovered. 
 
 It is to the medical student and practitioner, however, that 
 the microscope especially commends itself for its utility. A 
 new branch of medical study histology has been created by 
 its means alone ; while its contributions to morbid anatomy and 
 physiology, or pathology, are indispensable to the student or 
 physician who would excel, or even keep pace with the progress 
 of others, in his profession. To such the following remarks 
 will doubtless be interesting. 
 
 Histology is that science which treats of the minute or ulti- 
 mate structure and composition of the different textures of 
 organized bodies. It is derived from itfros, a tissue or web, 
 and Xoyoc:, a discourse. 
 
HISTORICAL INVESTIGATION. 15 
 
 The attempts made by the early microscopic observers to de- 
 termine ultimate structure, were in general of little value, 
 partly on account of the imperfections in the instruments em- 
 ployed, and partly from the mistakes they made in judging of 
 the novel appearances presented to their view. This last cause 
 of error still exists, and inexperienced observers may very 
 readily be led astray. By such, a fibre of cotton upon the 
 stage of the microscope, moving in obedience to the hygrometric 
 influence of the breath or of a moist atmosphere, might be re- 
 garded as a living animal ; or the influence of various reagents 
 on pus, mucus, blood, or other matters, might lead to error. 
 This last was the case with the celebrated Borelli, who was 
 the first to apply the microscope to the examination of struc- 
 ture. 
 
 Borelli was born in 1608, and lectured as professor in the 
 University of Pisa in 1656. In his day a general idea pre- 
 vailed, that diseases were occasioned by animalculse existing in 
 the animal tissues and fluids. An examination of abnormal 
 fluids with the microscope favored this idea, as the globules 
 were immediately taken for living beings. Borelli described 
 the pus globules as animalcules, and even says he has seen them 
 delivering their eggs. It will be seen that this was a very 
 natural mistake, when we remember that these globules contain 
 several minute granules, which make their escape when the 
 external envelope is broken or dissolved. In this way we 
 often find the germs of truth in the curious speculations of the 
 early microscopists. 
 
 Malpighi was the first to witness the most beautiful sight 
 which the microscope can reveal, the actual circulation of the 
 blood, thereby demonstrating the reasoning of Harvey to be 
 true. The first work he published, in 1661, comprises his 
 microscopic observations relative to the structure of the lungs. 
 Between this period and 1665, he published other tracts on the 
 
16 THE MICROSCOPIST. 
 
 minute anatomy of the kidneys, spleen, liver, membranes of 
 the brain, &c., and several of the structures still retain his name. 
 He also paid attention to the anatomy and transformations of 
 insects, the development of the chick in the egg, and the struc- 
 ture of plants. It will be perceived from the last remark, that 
 the intimate connexion between animal and vegetable physiology 
 was even then acknowledged. This connexion has led to the 
 establishment of the cell doctrine, or the theory of the develop- 
 ment of all organized tissues from cells. 
 
 Lewenhoeck has sometimes been called the father of micro- 
 graphy. He was born at Delft, in Holland, in 1663, and 
 appears to have received a rather indifferent early education. 
 He first brought himself into notice by the skill with which he 
 ground glasses for microscopes and spectacles, and for improve- 
 ments in those instruments ; thus affording a good model for 
 microscopic observers : first attending to the optical and 
 mechanical construction of the instrument he was to employ. 
 In 1690 he discovered and demonstrated the capillary blood- 
 vessels. He opposed the chemical doctrines which then reigned 
 in medicine, which attributed disease to fermentation in the 
 blood. He objected ; that if fermentation existed, air bubbles 
 would be seen in the vessels, which was not the case. He 
 showed that the blood-globules were of different sizes and forms 
 in various tribes of animals ; examined the brain and nerves, 
 the muscles, the crystalline lens, the milk, and numerous other 
 textures and fluids ; and made the interesting discovery of the 
 spermatozoa, which he conceived to be of different sexes. There 
 can be no doubt that he made numerous errors, but the whole 
 subject being new, his errors were excusable; and his contribu- 
 tions to science are still of the highest interest. 
 
 Swammerdarn, Lyonet, and Ellis, after this period, greatly 
 extended our knowledge of the lower tribes of animals; while 
 
HISTORICAL INVESTIGATION. 17 
 
 Lieberkuhn, Fontana, and Hewson labored successfully in the 
 department of histology. 
 
 To Lieberkuhn we owe the first good account of the anatomy 
 of the villi, and of the minute tubular glands of the small 
 intestine, which still bear his name. As a minute injector he 
 has never been surpassed. 
 
 Fontana examined the brain, nerves, muscles, and several 
 other textures, with great care, and his observations were ex- 
 tremely accurate. 
 
 Hewson is celebrated for his accurate observations on the 
 blood and lymph corpuscles. He first demonstrated that the 
 blood-globules were flat, with a central nucleus, and not round, 
 as had been previously supposed. < -' 
 
 Nearly all the celebrated men alluded to, made use of the 
 simple microscope. At this period the compound microscope 
 was very defective. It was more of a toy than a scientific 
 instrument. 
 
 From an ignorance of many phenomena connected with the 
 microscope which are now well understood, many errors re- 
 sulted. Optical illusions were mistaken for natural appear- 
 ances, as was the case with Monro. In his discoveries respect- 
 ing the brain and nerves, he describes them as being formed 
 of convoluted fibres, and in his examination of other textures 
 he saw the same fibres and always mistook them for nerves. 
 The fact was, that he made his observations while the direct 
 rays of the sun were transmitted through the substance under 
 examination, and the optical phenomena which were produced 
 led to the mistake. He afterwards found them on the surface 
 of metals, and then frankly acknowledged his error. 
 
 Another source of early errors was the treatment to which 
 their preparations were subjected before examination. It is 
 now well known that animal tissue should be examined while 
 fresh and transparent. What result is it possible to draw from 
 
 2* 
 
18 THE MICROSCOPIST. 
 
 the observations of those who boil, roast, macerate, putrefy, 
 triturate, and otherwise injure the delicate tissues ? Most of 
 the tissues contain albumen, which, so treated, gives origin to 
 globules, and flakes of different forms ; a circumstance which 
 has led several anatomists to conceive the basis of animal 
 structures to be globular. Several late observers have also 
 made this mistake. 
 
 Messrs. Todd and Bowman, the learned authors of " The 
 Physiological Anatomy and Physiology of Man," present the 
 following sensible remarks respecting this subject, " To make 
 microscopical observation really beneficial to physiological 
 science, it should be done by those who possess two requisites : 
 an eye, which practice has rendered familiar with genuine 
 appearances as contrasted with those produced by the various 
 aberrations to which the rays of light are liable in their passage 
 through highly refracting media, and which can quickly 
 distinguish the fallacious from the real form; and a mindj 
 capable of detecting sources of fallacy, and of understanding 
 the changes which manipulation, chemical reagents, and other 
 disturbing causes may produce in the arrangement of the ele- 
 mentary parts of various textures. To these we will add 
 another requisite, not more important for microscopical than 
 for other inquiries ; namely, a freedom from preconceived 
 views or notions of particular forms of structure, and an ab- 
 sence of bias in favor of certain theories, or strained analogies. 
 The history of science affords but too many instances of the 
 baneful influence of the idola spectis upon the ablest minds ; 
 and it seems reasonable to expect that such creatures of the 
 fancy would be especially prone to pervert both the bodily and 
 the mental vision, in a kind of observation which is subject to 
 so many causes of error, as that conducted by the aid of the 
 microscope." 
 
 The invention of the achromatic object-glasses for micro- 
 
HISTORICAL INVESTIGATION. 19 
 
 scopes formed the beginning of a new epoch in histological pur- 
 suits. Since that period, the confusion and opposition which 
 formerly existed among observers have diminished, and at 
 present only those differences remain which are incident to the 
 pursuit of any other branch of scientific study. 
 
 In our own times, the Germans seem to have taken the lead 
 in histological observations; and the reputation of the well- 
 known names of Ehrenberg, Miiller, Schwann, Schulz, Wagner, 
 Weber, and Valentin, principally depends on the discoveries 
 they have made by means of the microscope. 
 
 In England, the names of Carpenter, Todd, Bowman, Owen, 
 Cooper, Busk, Quekett, Bowerbank, and others, are connected 
 with microscopic research. 
 
 In our own country, a spirit of emulation seems excited 
 which promises great advantage. Professor Bailey of West 
 Point, and our townsmen, Drs. Leidy and Goddard, may be 
 mentioned among others who have contributed to this result. 
 The recent lectures of Dr. Goadby (late minute dissector to 
 the Royal College of Surgeons, England), on microscopic 
 science have done much to increase a desire on the part of 
 medical students and others to become practically acquainted 
 with this subject. His lectures to the students of the Phila- 
 delphia College of Medicine, and at other places, were well 
 attended ; as likewise were his private classes. Of his valu- 
 able suggestions I have frequently availed myself. 
 
 The advantage of a practical acquaintance with the micro- 
 scope by medical men may be easily seen, and is readily 
 acknowledged. Dr. Bennet, of Edinburgh, to whom I am 
 indebted for much of the histological part of this introduction, 
 says " I have lately had many opportunities of satisfying 
 myself that death may be occasioned by structural changes in 
 the brain which are altogether imperceptible to ordinary vision 
 and which have escaped the careful scrutiny of the first morbid 
 
20 THE MICROSCOPIST. 
 
 anatomists in this city. Again, who would have imagined that 
 porrigo favosa, mentagra, aphtha, and other diseases, consist of 
 cryptogamous plants growing on the skin or mucous mem- 
 branes ? Surely facts like these hold out a strong inducement 
 to the histologist who prosecutes pathological inquiries." In 
 another place he relates the following circumstance, which tends 
 to illustrate the same point : " A gentleman who had an ab- 
 scess in the arm, observed one morning his urine to be turbid, 
 and to deposit a considerable sediment. The practitioner who 
 attended him thought it looked like purulent matter, but before 
 finally forming his diagnosis, he asked me to examine it with 
 the microscope. I did so ; but instead of finding pus corpus- 
 cles, discovered a large quantity of irregularly formed granules, 
 which I recognised to be fibrinous. I immediately suggested 
 that the abscess was on the point of resolution, and I after- 
 wards learned, that from that time it rapidly disappeared. 
 The fact that fibrin exuded into the tissues, and, subsequently 
 absorbed, passes off by the kidneys, was determined by the 
 microscopic observations of Schonlein and Zimmerman in Ger- 
 many/' 
 
 Many other instances might be adduced, were it necessary, 
 to show the importance of the microscope in diagnosis and in 
 practical medicine. It is not too much to hazard the assertion, 
 that in a few years the practitioner will find it as essential in 
 finding out the nature of disease, and the state of the system, 
 as the most valuable articles of the niateria medica are useful 
 in medical treatment. The following example will illustrate 
 the delicacy as well as utility of this mode of investigation. 
 A few evenings since, while entertaining a friend with some 
 microscopic views, he expressed a wish to see the red globules 
 of the blood ; so, pricking the tip of his finger with a lancet, a 
 drop was extracted, which, after covering with thin glass, was 
 placed upon the stage of the microscope. Observing the glo- 
 
HISTORICAL INVESTIGATION. 21 
 
 bules, with a greater tendency than usual, to run together into 
 rows, like piles of coin, I remarked to him that his blood 
 assumed an inflammatory or a feverish appearance. He replied, 
 that he had been for about thirty-eight hours without sleep, 
 having sat up with a sick friend the night before, and having 
 some gastric irritation in addition, he had felt feverish all the 
 evening. Observations on pus, mucus, the urine, and the 
 various forms of malignant tumors, &c., all exhibit the value 
 of this instrument to medical science. 
 
 In medico-legal researches the microscope has already proved 
 a valuable auxiliary. It has several times been employed to 
 ascertain the true nature of spots suspected to be blood-stains, 
 &c. ; and in cases where human life was suspended upon its 
 decision. 
 
 In 1837, M. Ollivier was directed to ascertain whether any 
 human hair was attached to the blade of a hatchet seized in 
 the house of a person suspected of murder, and if this were 
 the case, to determine the color of the hair. With the micro- 
 scope, M. Ollivier ascertained that the filaments attached to 
 the hatchet were the hairs of an animal, and not of a human 
 being ; and this was afterwards fully proved. 
 
CHAPTER II. 
 
 THE MICROSCOPE. 
 
 THOSE who have examined a common magnifying glass (or 
 lens) know that it is necessary to hold it exactly at a certain 
 distance from the object viewed through it, in order that such 
 object may be seen with distinctness. The point at which the 
 object must be placed is called the focus of the lens, and the 
 distance from the middle of the lens to the focus is the focal 
 length, or focal distance of the lens. 
 
 The cut represents sections of the different forms of lenses. 
 A, is a plano-convex lens. B, double convex. C, plano-con- 
 cave. D, double concave. E ; a meniscus. 
 
 Fig. 1. 
 C 
 
 The effect of the convex lens or of the meniscus is to cause 
 the rays of light which pass from any object through them, to 
 converge towards a point or focus ; and the eye receiving those 
 
THE MICROSCOPE. 23 
 
 rays after passing through the lens, sees the object apparently 
 magnified. This principle is the basis upon which all micro- 
 scopes are constructed. 
 
 The concave lens produces a precisely contrary effect to that 
 described above. The rays of light diverge on passing through 
 it, and the object appears diminished in size. 
 
 SIMPLE MICROSCOPES. 
 
 A piano or double convex lens, especially when mounted, or 
 arranged with conveniences for viewing objects, is called a 
 simple microscope. 
 
 The magnifying power of a simple microscope is in propor- 
 tion to the shortness of its focal length. Thus, a lens of 2 
 inches focal distance, magnifies 5 diameters (or the superficies 
 25 times) of 1 inch focus, 10 diameters |ths of an inch, 15 
 diameters inch, 20 diameters i inch, 40 diameters gth 
 inch, 80 diameters J^th inch, 100 diameters. 
 
 This table of magnifying powers is not invariably correct, 
 owing to the difference of vision in different individuals, but it 
 is sufficient for all practical purposes. 
 
 Simple microscopes are mounted in a variety of ways, ac- 
 cording to the purposes for which they are intended. Some 
 are made to turn upon a hinge into a case, so as to carry in the 
 pocket; and others are fixed on a handle, with a pin or small 
 pair of forceps in the focus, on which a small object, as an 
 insect, &c., may be placed. 
 
 The cut, Fig. 2, exhibits the arrangement of Dr. Withering's 
 Botanical Microscope, which is valuable from its simplicity. 
 It consists of three brass plates, a, I, c, parallel with each other, 
 
24 THEMICROSCOPIST. 
 
 to the upper and lower of which the stout wires, d, e } are rivet- 
 ted. The middle plate, b, which forms the stage for carrying 
 the objects, is made to slide up and down on these wires. The 
 upper plate, a, carries the lenses, i, and the lower one, c, some- 
 times carries a mirror, for reflecting the light of a candle or of 
 the sky through any transparent object which may be placed 
 on the stage. Into the stage a dissecting knife, h, a pointed 
 
 Fig. 2. 
 
 instrument, /, and a pair of forceps, </, are made to fit, and can 
 be readily taken out for use by sliding the stage down nearly 
 to the mirror. 
 
 A very useful kind of simple microscope was that invented 
 by Mr. Wilson ; an early form of which is represented by Fig. 
 3. The body, A, A, A, A, which was made either of ivory, brass, 
 or silver, was cylindrical, and about two inches in length, and 
 one inch in diameter. Into the lower end, B, the magnifiers 
 are screwed, and into the upper end screws a piece of tube, D, 
 carrying at the end, C, a convex glass, and on its outside a 
 male screw. Three thin plates of brass, E, are made to slide 
 
THE MICROSCOPE. 
 
 25 
 
 easily in the inside of the body to form the stage. One of 
 these plates, F, is bent semicircularly in the middle, for the 
 reception of a tube of glass, for viewing the circulation of the 
 
 Fig. 3. 
 
 blood in small fish, while the other two are flat, and between 
 these last the object-sliders, K, are introduced. Between the 
 stage and the end of the body, B, is a bent spring of wire, H, 
 to keep the stage and object steadily against the screw-tube. 
 The object is adjusted to the focus by turning the screw D. 
 This instrument was held in the hand in such a position that 
 the light of a lamp or candle might pass directly into the con- 
 
26 
 
 THE MICROSCOPIST. 
 
 densing glass. It was afterwards improved by the addition of 
 a handle placed at right angles to its body. 
 
 The best form of the simple microscope for viewing opaque 
 
 Fig. 4. 
 
 objects, is that represented by Fig. 4 : a is a flat piece of brass 
 attached to the handle, p', it supports the lens-holder, i t and 
 through it passes the screw, &, which is connected to the back- 
 plate, c ; a spring, e, keeps the plates, a, c, apart, and the nut, 
 
THE MICROSCOPE. 27 
 
 d, adjusts the lens to the focus of the object, either on g or h. 
 But the chief merit in its construction consists in a concave 
 speculum or mirror of silver, &, highly polished, to the centre 
 of which, at Z, the magnifying glass is adapted. This is screwed 
 into the ring i, and so held that a bright light, as from a can- 
 dle or white cloud, is received upon the speculum (called a 
 Lieberkuhn, from the name of its inventor). The light so 
 received is concentrated upon the object, which is brightly 
 illuminated; and is adjusted to the focus of the lens by turning 
 the nut d. 
 
 For minute dissection of animal or other tissues, which is 
 generally performed under water, as hereafter described, the 
 
 Fig. 5. 
 
 microscope of Mr. Slack, with the improvements of Dr. H. 
 Goadby, F.L.S., is the most efficient. The following is a de- 
 scription of the instrument employed by the latter gentleman 
 in his microscopic researches ; and with which he has made a 
 
28 THE MICROSCOPIST. 
 
 great number of beautiful preparations in minute anatomy, 
 entomology, &c. It consists of a box or case, which is repre- 
 sented by A, Fig. 5. The upper surfaces r, r, are sloped off to 
 form arm-rests. The front of the case (which is not seen in 
 the cut) is furnished with a flap or door, which has hinges at 
 the bottom and a lock at the top ; so that the various parts of 
 the instrument may be packed up inside. 
 
 In the top of the box is a round hole, B, into which fits the 
 short piece of tube atttached to the tin box, C, which is designed 
 to hold the water in which the dissection is made. The ring, 
 D, is the lens-holder, which is adjusted to the proper focus by 
 means of the milled head, E, which moves the rack, F, up and 
 down, working inside the box A. The lens-holder has also a 
 horizontal motion, by means of the rack and pinion, G* Another 
 horizontal motion is produced by a swivel joint attached to F. 
 Inside the box is a mirror, directly under the hole B, so that 
 the light can be directed upwards through any transparent 
 object at B. 
 
 When moderate power only is needed, a simple microscope 
 is the best instrument which can be used ; and for the purpose 
 of making minute dissections it is also the most convenient; 
 but when a very high magnifying power is needed, combined 
 with distinctness of observation, a single (or simple) micro- 
 scope is found to be imperfect : although very small lenses 
 have been made, which magnify exceedingly quite enough 
 for all useful purposes. Good lenses, of a high magnifying 
 power, may be made by drawing out a very narrow strip of 
 glass in the flame of a spirit lamp, and upon the end of the 
 thread thus formed, running a small globule by means of the 
 flame, which may be detached from its thread and placed be- 
 tween two thin plates of metal in which a small hole has been 
 drilled. 
 
THE MICROSCOPE. 
 
 29 
 
 Optical Improvements in the Simple Microscope. There are 
 imperfections of vision attending the use of all common lenses ; 
 arising either from the shape of the lens, or from the nature of 
 light itself when passing through a refracting medium. These 
 imperfections are termed respectively, spherical and chromatic 
 aberrations. To lessen or destroy these aberrations various 
 plans have been proposed, with various success. Mr. Cod- 
 dington proposed a lens in the form of a sphere, cut away round 
 the centre, as at A, Fig. 6. This is an excellent form for a 
 hand lens, but is not often to be procured in this country, 
 opticians preferring to dispose of the Stanhope lens, seen at B, 
 
 k C} 
 
 which is more easily made than the Coddington lens, but is 
 inferior to it. C and D are doublets proposed by Sir John 
 Herschell; the first of which consists of two plano-convex 
 lenses, a, 5, whose focal lengths are as 2-3 to 1, with their 
 convex sides together; the least convex next the eye, D, 
 consists of a double convex lens, , next the eye, and a meniscus, 
 b. When these lenses are used for forming images the lenses 
 marked a should be next the object. 
 
 Other forms of doublets have been proposed, but by far the 
 
30 
 
 THE MICROSCOPIST. 
 
 best arrangement of this kind is Dr. Wbllaston's Doublet, 
 which consists of two plano-convex lenses, whose focal lengths 
 are as 1 to 3 ; the plane sides of each, and the smallest lens, 
 placed towards the object. The lenses are set in separate cells 
 so as to adjust their proper distance apart, which is best done 
 by experimenting on their performance, although their distance 
 is about the difference of their focal lengths. Between them is 
 a diaphragm or stop, generally placed immediately behind the 
 
 Fig. 7. 
 
 anterior lens. The stop was not employed by Dr. Wollaston, 
 as his lenses were of such high power that they nearly touched 
 
THE MICROSCOPE. 31 
 
 each other ; yet it is, nevertheless, found to be essential to a 
 good doublet. 
 
 A, C, Fig. 7, represent the lenses of the doublet, and B is 
 the diaphragm or stop. The manner in which the light is 
 refracted by this instrument, is shown by the lines proceeding 
 from each end of the object, 0. The dotted lines represent 
 the blue or most refrangible rays of the spectrum ; the others 
 are the red rays. Those rays which pass through the centre 
 of the lens, A, are caused to pass through the hole in the dia- 
 phragm over to the margin of B, and those nearest the margin 
 of A, pass next the centre of B ; and so become nearly cor- 
 rected : the imperfection of one being made to counteract that 
 of the other. 
 
 An improvement was made upon this by Mr. Holland, and 
 is called Holland's Triplet. It consists of a doublet in place 
 of the first lens, A, in the last figure ; retaining the stop be- 
 tween it and the lens C. This form is the highest stage of 
 perfection which the simple microscope has ever yet attained. 
 The great objection to its use, however, is, that it must be 
 brought into such close proximity to the object, that it is im- 
 possible to cover such object except with the thinnest mica, 
 which is objectionable on account of its liability to be scratched. 
 
 Before dismissing the subject of single microscopes, it may 
 be well to remark, that for a low magnifying power, a double 
 convex lens is the best to use ; but for medium or high powers, 
 a plano-convex lens, with the convex side towards the object ; 
 or one of the doublets just described; is preferable. 
 
 THE COMPOUND MICROSCOPE 
 
 Consists essentially of two convex lenses ; an object-glass and 
 an eye-glass ; as represented in Fig. 8. 
 
THE MICROSCOPIST. 
 
 A is the object-glass, which forms a magnified image of the 
 object at 0, which is further enlarged by the eye-glass B. An 
 
 Fig. 8. 
 
 additional lens, D, is usually added; for the purpose of en- 
 
THE MICROSCOPE. 33 
 
 larging the field of view. It is called the field-lens. An 
 inspection of the dotted lines in the figure will show that many 
 of the rays pass beyond the reach of the eye-glass, B : an 
 image from these rays is represented at E. These rays are 
 intercepted by the field-glass D, and form an image at F, which 
 is viewed by the eye-glass. 
 
 In looking through a common microscope of this kind, the 
 observer will probably see rings of color round the edge of 
 the field of view, and also similar colors around the edges of 
 the object he is viewing. These defects arise from the decom- 
 position of common white light j and are called chromatic 
 aberration or dispersion. The colors round the field of view 
 are produced by the defects of the eye-piece ; and those round 
 the object, by the object glass. Again : if the object be 
 looked at through the instrument as before, its outline or 
 edges will be observed, not sharp and distinct, but thick and 
 confused. This is caused by the rays not being collected into 
 a perfect point as they were on the object itself. This defect 
 is called spherical aberration. "When an instrument has 
 neither its chromatic nor spherical aberration removed, it is 
 said to be uncorrected. 
 
 To conceal these defects there is generally a small hole or 
 stop behind the object glass. This is injurious to correct 
 vision, as it prevents a large portion of light from entering the 
 eye, and makes the objects appear dark, so that their true 
 structure cannot be made out. When this is the case, the 
 instrument is said to want angular aperture. The stop refer- 
 red to, however, is essential even to the moderate performance 
 of a common instrument. 
 
 To obviate all these difficulties, improvements have been made 
 both in the object-glasses and the eye-pieces. Wollaston's 
 Doublet has been found capable, when used as an object-glass 
 with the Huygenian eye-piece (hereafter described), of trans- 
 
34 THE MICROSCOPIST. 
 
 mitting a large pencil of light with great distinctness, having 
 an angular aperture of from 35 to 50. Mr. Holland's 
 Triplet, used in the same way, is capable of transmitting a 
 pencil of 65 with distinctness and correctness of definition. 
 The achromatic object-glasses, as first proposed by Mr. Lister, 
 have however superseded all other attempts to improve the 
 compound microscope, and have raised it from the condition of 
 a mere toy to be the most valuable instrument of scientific 
 research. They are made of plano-concave flint, and double- 
 convex crown glass lenses, cemented together. Three com- 
 pound lenses form the object-glass for a microscope, as repre- 
 sented by Fig. 9, a, &, c. In object-glasses of a high power, 
 
 Fig. 9. 
 
 the anterior compound lens, a, has sometimes an adjustment to 
 render it suitable for objects either uncovered or covered with 
 glass of various thickness. The object-glass, thus made, is not 
 quite achromatic, being rather over-corrected as to color, but 
 is finally corrected by using the Huygenian eye-piece, shown in 
 Fig. 10. 
 
 This eye-piece consists of two plano-convex lenses A, B, with 
 their plane sides next the eye. In the focus of A is the dia- 
 phragm or stop, C. The proportions of the focal lengths of 
 these lenses should be as 3 to 1, and their distance apart, one- 
 half the sum of their focal distances. Thus if B be three 
 
THE MICROSCOPE. 35 
 
 inches focus, A should be one inch, and their distance apart 
 two inches. 
 
 Sometimes, when a very flat field of view is required, as in 
 the use of a micrometer eye-piece, the convex sides of the 
 lenses face each other. It is recommended that for this kind 
 of eye-piece the lenses should be nearly of the same focal 
 length, and at a distance equal to two-thirds the focal length of 
 either. 
 
 A good compound microscope should be furnished with 
 many mechanical conveniences, in addition to the optical part 
 just described. It should be capable of being steady in any 
 position from vertical to horizontal have coarse and fine ad- 
 justments for focus have a large and firm stage, with ledge, 
 clips, &c. ; and with traversing motions, so as to follow an 
 object quickly, or readily bring it into the field of view, and 
 should have a concave and plane mirror, of two inches diame- 
 ter, with a universal joint, and capable of being brought nearer 
 or farther from the stage, as likewise of reflecting a side-light. 
 
36 THE MICROSCOPIST. 
 
 A variety of forms have been given to the mechanism of the 
 compound microscope, many of which are very good, while 
 others are exceedingly objectionable. Suffice it to say respect- 
 ing them, that steadiness, or freedom from vibration, and 
 particularly freedom from any vibrations which are not equally 
 communicated to the object under examination and to the 
 lenses by which it is viewed, is a point of the utmost conse- 
 quence. A microscope body containing the lenses, screwed by 
 its lower extremity to a horizontal arm, is the worst form con- 
 ceivable. 
 
 The compound microscope consists of three parts the opti- 
 cal part, containing the object-glasses and eye-piece; the stage 
 for holding the object ; and the illuminating apparatus, which 
 is either a mirror below the stage for transparent objects, or 
 an illuminating lens for those which are opaque. Whatever 
 form may be given to the mechanical arrangement, the parts 
 alluded to are found in all, and the principles of their manage- 
 ment are the same. 
 
 The most celebrated artists in the manufacture of these 
 instruments are Powell and Lealand; Ross; and Smith and 
 Beck, of London. A microscope from the latter firm is repre- 
 sented in the opposite cut. 
 
 The body slides by a rack and pinion, moved by the milled 
 head, a, on a strong dovetailed bar ; and has also a slow mo- 
 tion for delicate adjustment of focus, given by the milled head 
 b. It is furnished with a sliding tube, c, for varying its length ; 
 and with three sliding Huygenian eye-pieces, tZ, d f , d", of 
 successive powers. 
 
 The erecting glasses, ?/, are to be screwed, when employed, 
 into the other end of the sliding tube. They rectify the 
 image, which is inverted when seen in the usual way. Their 
 chief advantage is in microscopic dissection. 
 
 The stage has two steady rackwork motions, at right angles 
 
THE MICROSCOPE. 37 
 
 to each other and to the axis of the body, given by the milled- 
 heads, e, e f ; it has also a sliding and revolving plane, /, with 
 a ledge, </, for resting object-slips upon, and a sliding-piece, A, 
 with springs for clamping them. An upright rod, i, is fixed 
 on this plane for mounting the forceps, v y or for the spring- 
 holder, y, when a glass trough, u, is used. A profile of the 
 glass trough, with its diagonal plate of glass for conforming an 
 object, is seen at u f . At z, is a three-pronged forceps. 
 
 A large double mirror, &, concave on one side and plane on 
 the other, is supported by the cylindrical bar, Z, and may be 
 moved upon it vertically and sideways. 
 
 A movable diaphragm, m, is fixed under the stage for vary- 
 ing the quantity and direction of the light when transparent 
 objects are viewed. The illuminating lens, n, is used for con- 
 densing light upon opaque objects ; and a silver side-reflector 
 is for the same purpose. The bull's-eye lens, for increasing the 
 illumination, is seen at r. 
 
 An achromatic condenser, x, slides into the place of the 
 diaphragm, to give the utmost refinement to the illumination of 
 transparent objects. 
 
 The live-box, s, is for observing living objects between two 
 glass plates ; and a second live-box, s', with screw collar, for 
 objects in water. The screw is for regulating the depth of 
 water, and the degree of pressure employed. 
 
 A plate of glass, t, with a ledge, has a separate piece of thin 
 glass to lie upon it, for viewing animalcules, &c., in water. 
 
 The camera lucida, w, has its prism fixed on a short tube 
 with a slight side motion for adjustment, and fits on each eye- 
 piece when its cap is removed. 
 
 The three Lieberkuhns, o, o', o", adapted to the object- 
 glasses 2, 3, and 4, are applied by sliding them in front of 
 each respectively. When one of these is used, the diaphragm 
 is to be removed, and the dovetailed piece, p, may be slid in its 
 
 4 
 
88 THEMICROSCOPIST. 
 
 place, with one of the three dark wells or stops, p, p'ip"i which 
 will make a dark background. If the objects are mounted on 
 circular discs, g, the well will not be needed. 
 
 The object-glasses comprise four powers. No. 3 and No. 4 
 have the tube of their front lens movable, for adjusting their 
 performance with objects either uncovered or covered with thin 
 glass. The graduated screw collar, by which the adjustment is 
 made, is seen at 5. 
 
 The high price of these instruments must necessarily put 
 them out of the reach of those whose means are limited, and 
 our opticians seldom import them, except to order. Of late, 
 however, a praiseworthy effort has been made to simplify the 
 construction of the mechanical parts, so as to bring the price 
 within the control of the generality of medical men and other 
 students of nature. Mr. J. B. Dancer, Manchester, England, 
 furnishes a very complete microscope, with two object-glasses 
 and the necessary apparatus, for 10. Messrs. Powell and 
 Lealand have also fitted up an instrument with a stand of cast- 
 iron, whose cost, exclusive of the object-glasses, is 9. Other 
 manufacturers are also pursuing the same course. 
 
 From the cause above referred to, the majority of micro- 
 scopes used in this country are of French or German manufac- 
 ture. Chevalier and Oberhauser have furnished some excellent 
 instruments; but the mechanism not allowing the mirror to 
 turn aside from the axis of the instrument, so as to give a side 
 light, is a serious objection to them, although the optical part 
 is often very little inferior to the English. 
 
 Dr. Bennet, of Edinburg, highly recommends Oberhauser's 
 instruments to medical men. He advises the employment of 
 the No. 3 and No. 7 object-glasses, answering to the i inch 
 and 1 inch lens of the London opticians. 
 
 Hitherto, the fashion in this country in regard to microscopes, 
 has led to the almost universal employment of high powers, to 
 the neglect of the others, so that it is exceedingly difficult to 
 
THE MICROSCOPE. oU 
 
 procure an achromatic object-glass with shallow magnifiers, not- 
 withstanding the decided advantage to be derived from their use. 
 
 The microscopes of M. Nachet, and M. Brunner, of Paris, 
 have been highly recommended. Those of the former which I 
 have seen, are about on a par with the instruments made by 
 Oberhauser, with the advantage of a larger stage. 
 
 Mr. C. A. Spencer, of Canastota, New York, has succeeded 
 in manufacturing object-glasses, which are said to have an 
 angle of aperture even greater than the best English achro- 
 matics. With them he succeeded in resolving the fine markings 
 on the Navicula Spencerii, since adopted as one of the most 
 difficult test objects. 
 
 A communication from Dr. J. L. Smith, to Silliman's 
 Journal, describes the results of an examination of three micro- 
 scopes by different makers. From this it would seem that for 
 high powers, the object-glasses of Ross are the best, Spencer's 
 rank next, while Nachet' s are not much inferior. 
 
 The best defining object-glass I have yet seen is one I have 
 made by combining two of Oberhauser' s with one of Chevalier's, 
 so as to make a triple objective. With this the sets of markings 
 on the Navicula Angulata are beautifully seen by oblique light. 
 
 Such are the practical difficulties attending the production of 
 such delicate instruments, that there must be a very great 
 difference in the glasses even of the same maker, so that before 
 purchasing an instrument, it is always best to examine it by 
 means of some of the test objects hereafter described. 
 
 REFLECTING MICROSCOPES, 
 
 In which the image was formed by a concave mirror instead 
 of a lens, are not now so much used as formerly. They are 
 generally complicated in structure, and are surpassed and 
 therefore superseded by the achromatic microscope. 
 
 The following is a simple reflecting microscope, invented by 
 Mr. S. Gray, and may be of some interest from its singularity. 
 
40 
 
 THE MICROSCOPIST. 
 
 A, Fig. 11, represents a brass ring, one-thirtieth of an inch 
 thick, whose inner diameter is about two-fifths of an inch. 
 Having dissolved a globule of quicksilver in one part nitric 
 acid and ten parts water, he rubbed with it the inner surface 
 
 of the ring, which became silvered ; having wiped it dry, he 
 put a drop of quicksilver within it, which, when pressed with 
 the finger, adhered to the ring, and formed a convex speculum. 
 When the ring was taken up carefully, and laid on the margin 
 of the cylinder, B, the mercury sank down, and formed a 
 concave reflecting speculum. The cylinder, B, is supported by 
 a pillar, which is attached to the foot, D. The stage, Gr, is 
 for holding the object, and is adjusted to the focus by the screw 
 atC. 
 
CHAPTER III. 
 
 ADJUNCTS TO THE MICROSCOPE. 
 
 IN addition to the mirror, object-glasses, eye-glasses, and 
 the parts constituting the stand of a microscope, several acces- 
 sory instruments are needed by those who would devote atten- 
 tion to microscopic researches. The most necessary or useful 
 of these we proceed to describe. 
 
 The Diaphragm, for cutting off extraneous light when 
 
 Fig. 12. 
 
 viewing minute transparent objects, consists of a plate of brass 
 perforated with several holes of different sizes. This revolves 
 on a pivot, so as to bring each hole in succession under the 
 object-glass. It is adapted under the stage of the instrument, 
 and is so essential in practice that few microscopes are made 
 without it. 
 
 The Condenser. This is an arrangement under the stage 
 4* 
 
42 THE MICROSCOPIST. 
 
 for condensing the light upon the object. The best instruments 
 employ an arrangement of achromatic glasses, similar to the 
 object-glasses, but its value is scarcely equal to its cost. The 
 Wollaston Condenser is a short tube, in which a plano-convex 
 lens of three-fourths of an inch focal length, with its flat side 
 towards the object, is made to slide up and down. Dr. Wollas- 
 ton employed a long tube with a stop between the lens and the 
 mirror, but Dr. Goring found it better to have the stop be- 
 tween the lens and the object, and a little out of the axis of 
 the lens. 
 
 A substitute for the achromatic condenser is found in Mr. 
 Varley's dark chamber. This is sometimes preferable to the 
 Wollaston Condenser, as the light is not decomposed by pass- 
 ing through a lens. 
 
 c, Fig. 13, is a plate of brass adapted to the stage, in which 
 is a short tube having a diaphragm or stop, a, whose aperture 
 
 is equal to what can be viewed by the microscope, and no 
 larger. Below is a sliding tube, 6, with an aperture rather 
 larger than that at a. This last can be moved up and down 
 until the light at a is of the greatest intensity. The aperture 
 at a is always in proportion to the object-glass employed. 
 
 Condensers for oblique illumination. As the lines on some 
 test objects require an illumination at a considerable angle from 
 the axis of the microscope, various plans have been suggested 
 for the purpose. The most simple mode is to turn aside the 
 
ADJUNCTS TO THE MICROSCOPE. 43 
 
 concave mirror from the axis* of the instrument, but in this 
 way the illumination is confined to one side of the object while 
 the other side is in shadow. M. Nachet has contrived an 
 oblique prism which can be revolved so as to throw oblique 
 light successively on all parts of the object. Mr. Wenham's 
 illuminator consists of a truncated parabolic mirror (somewhat 
 the shape of the half of an egg-shell with about half an inch of 
 the apex cut off) fastened beneath the stage plate. At the 
 bottom of this mirror is a circular stop of the size of the 
 opening at the other end. This carries a dark well up nearly 
 to the stage plate. When this illuminator is used the light 
 is thrown up by means of the plane mirror, and by reflexion 
 from the parabola is made to pass behind and around the dark 
 well. Direct light is prevented by the circular disc or stop. 
 This is a most admirable contrivance. The objects appear 
 brilliantly illuminated on a dark ground. The illuminator 
 usually has a meniscus at the small end to correct the aber- 
 ration of the slip of glass which carries the object. 
 
 Nobert's illuminator, like the last, throws an oblique 
 light all round an object, and of course there is no shadow. 
 It consists simply of a thick plano-convex lens, in the centre 
 of the convex surface of which a deep concavity is made. The 
 plane side is turned towards the object, and it is placed in a 
 manner similar to the Wollaston Condenser. The concavity 
 in the lens is equivalent to a dark spot on the convex surface, 
 so that a hollow cone of light is obtained, in the apex of which 
 the object is placed. It is necessary to have lenses of different 
 sizes for object-glasses of different focal lengths. 
 
 Polarizing Apparatus (Fig. 14), for viewing objects by 
 polarized light. It consists usually of two prisms of calca- 
 reous spar, in proper tubes; one below the stage, and the 
 other in the eye-piece. Sometimes a thin piece of tourmaline 
 is used in place of the prism in the eye-piece. 
 
44 
 
 THE MICROSCOPIST. 
 
 Fig. M. 
 
 Erector. This is sometimes supplied with the best instru- 
 ments. It consists of a pair of lenses acting like the erecting 
 eye-piece of the telescope. It is applied to the draw tube at 
 the end of the eye-piece towards the object-glass. It is only 
 used when it is desired to dissect with the compound micro- 
 scope, as, without it, the position of the object appears re- 
 versed. 
 
 Condensing Lens and Lamp. The Wollaston Condenser, 
 &c., is designed to concentrate the light which comes from the 
 mirror, directly upon the object; but the condensing lens and 
 lamp is used either for opaque objects, or to condense the light 
 upon the mirror itself. Two such lenses, as in the figure, are 
 generally used. Dr Goadby informed me, that after many 
 experiments he has found a bull's-eye lens, of three inches 
 focal length, the most efficient for the larger lens ; and after 
 several trials with different sorts of lenses I am disposed to 
 agree with him. Fig. 15 illustrates one mode of using the 
 condensers upon opaque objects. A, is the bull's-eye lens, 
 
ADJUNCTS TO THE MICROSCOPE. 
 
 45 
 
 which turns upon its axis, and slides up and down a stout wire 
 affixed to a steady foot. B, is the smaller lens, whose handle 
 
 Fig. 15. 
 
 slides through a socket, working on a hinge-joint. Sometimes 
 a lens of this kind is affixed to the stage of the microscope, 
 when it can be used in combination with the bull's-eye lens, 
 or alone. C, is the object upon which the light is concen- 
 trated. D, the lamp. To condense the light on the mirror, 
 the lens, A, alone is used. The lamp is of the kind called a 
 fountain lamp, and slides up and down a stem, on which it can 
 be fixed at any height by a screw. A shade should always 
 be used with the lamp, in order to screen the eye as much as 
 possible from any light save that which proceeds through the 
 instrument. As it is a matter of much consequence to our 
 observations that we should have a steady intense light, it is 
 not immaterial what kind of oil, &c., we employ. After many 
 trials and disappointments, I am convinced that pure sperm oil 
 is the pleasantest, cheapest, and best. Caraphene, burning- 
 fluid, and gas give out a very intense light, but there is a 
 tremulous motion in the flame, which is somewhat unpleasant. 
 
46 
 
 THE MICROSCOPIST. 
 
 Lieberkuhn, or Silver Cup. This is a most useful instru- 
 ment for viewing opaque objects. It is attached to the object- 
 glass in the manner represented by Fig. 16, where a is the 
 lower end of the body of the microscope, b the object-glass, 
 
 Fig. 16. 
 
 to which the Lieberkuhn, c, is attached. The rays of light 
 reflected from the mirror, are brought into a focus upon an 
 object, (7, mounted in the usual way upon glass, or held in 
 the forceps, /. When the object is transparent, or is too small to 
 fill up the entire field of view, the dark well or stop, e, is used. 
 This is generally fixed into the centre of the stage, a little 
 below the upper surface. Sometimes, instead of a Lieberkuhn, 
 a side-reflector is used, and from the greater obliquity of its 
 reflection, is of great advantage in exhibiting delicate struc- 
 tures. 
 
 It has hitherto been considered impracticable to use very 
 high powers with opaque objects, but the Athenaeum informs 
 us that " at one of Lord Rosse's recent scientific soirees, Mr. 
 Brooke showed his new method of viewing opaque objects 
 under the highest powers of the microscope (the |th and yjth 
 
ADJUNCTS TO THE MICROSCOPE. 47 
 
 inch object-glasses). This is performed by two reflections. 
 The rays from a lamp, rendered parallel by a condensing lens, 
 are received on an elliptic reflector, the end of which is cut off 
 a little beyond the focus, as in Wenham's illuminator for 
 oblique light ; the rays of light converging from this surface 
 are reflected down on the object by a plain mirror attached to 
 the object-glass, and on a level with the outer surface. By 
 these means the structure of the scale of the podura, and the 
 different characters of the inner and outer surface, are rendered 
 distinctly visible." I have not had an opportunity of testing 
 this plan, but have little doubt of its success. 
 
 Camera Lucida. By which drawings are made from the 
 microscope. This is generally formed by placing a small prism 
 of glass, inclined at the proper angle, in front of the eye-piece. 
 In Fig. 17, a, represents the camera, formed of highly-polished 
 
 Fig. 17. 
 
 steel, smaller than the pupil of the eye, inclined at an angle 
 of 45, and fixed to a clip, b, which embraces the eye-piece. 
 
 Frog-plate; Fig. 18; on which frogs or fish are tied to ex- 
 amine the circulation of blood in their vessels. The frog, &c., 
 must first be enclosed in a bag, and fastened on the plate by 
 the holes in either side of it. Then thread is tied to about 
 
48 
 
 THE MICROSCOPIST. 
 
 four of its toes, and the web is spread out over the large hole 
 by fastening the ends of the thread through the small holes 
 in the plate. 
 
 Fig. 18. 
 
 The Stage Micrometer consists of a slip of glass, pearl, &c., 
 having a line finely divided into parts of an inch, &c. To 
 obtain with this the power of a compound microscope, compare 
 the divisions seen with one eye through the instrument, with 
 a rule held ten inches off, and looked at with the other eye. 
 Suppose, for instance, the micrometer be divided into -j-J^ths 
 of an inch, and one of these divisions covers an inch of the 
 rule seen with the other eye, the magnifying power of the 
 instrument is 100 diameters. If it should cover five inches, 
 it is magnified 500 diameters. By sketching the object by 
 means of the camera, and then putting in its place a stage 
 micrometer, and marking the divisions over the sketch, they 
 can again be subdivided, and so the measure of an object 
 be accurately taken. 
 
ADJUNCTS TO THE MICROSCOPE. 49 
 
 Animalculce Cage is a round cell with a glass bottom and 
 top, for confining a drop of water with animalculae. 
 
 Fig. 20. 
 
 Watch- Glasses and Fishing Tides, are useful adjuncts. The 
 latter, Fig. 19, are glass tubes of various sizes, by which when 
 
 5 
 
50 THE MICROSCOPIST. 
 
 one end is closed with the finger a quantity of water, &c., may 
 be lifted from a phial, as seen at Fig. 20, and put in a watch- 
 glass. By their aid, too, with a little practice, an animalcula 
 may be caught in a phial, when it is visible to the naked eye. 
 With the finger on one end of the tube, approach the other 
 end to the place where the animal is, then suddenly lifting off 
 the finger, the current will carry it into the tube. 
 
 A Compressor ium, for applying pressure to an object ; a 
 trough for chara and polypi ; a phial-holder, &c. ; will also be 
 found useful. 
 
CHAPTER IV. 
 
 HOW TO USE THE MICROSCOPE. 
 
 MANY persons imagine that the value of a microscope is in 
 proportion to the apparent size of an object seen through it. 
 This, however, is a mistake. The greater the magnifying 
 power of an instrument, all other things being equal, the 
 greater is the difficulty of finding a minute object on the stage, 
 and of adjusting the focus. The light, too, transmitted from 
 the mirror, becomes less intense, and the view less satisfactory 
 with the use of high powers. For the majority of objects, a 
 low or medium power is always preferable, on account of the 
 greater extent of the field of view. The test objects, however, 
 and the minute structure of any delicate tissue, &c., require 
 very considerable amplification in order to exhibit them satis- 
 factorily. When this is the case, the increase of power should 
 be given by the employment of an object-glass of shorter focal 
 length, in preference to the use of a more powerful eye-piece. 
 
 Sir David Brewster gives the following rules for microscopic 
 observations. 
 
 1. The eye should be protected from all extraneous light, 
 and should not receive any of the light which proceeds from 
 the illuminating centre, excepting what is transmitted through 
 or reflected from the object. This rule will illustrate the use 
 of the diaphragm under the stage of the microscope. 
 
 2. Delicate observations should not be made when the fluid 
 which lubricates the cornea of the eye is in a viscid state. 
 
52 THEMICROSCOPIST. 
 
 3. The best position for microscopic observations is when 
 the observer is lying horizontally on his back. This arises 
 from the perfect stability of the head, and from the equality 
 of the lubricating film of fluid which covers the cornea. The 
 worst of all positions is that in which we look downwards ver- 
 tically. The most common and easy position is generally with 
 the instrument inclined at an angle of 45 degrees. 
 
 4. If we stand straight up and look horizontally, parallel 
 markings or lines will be seen most perfectly when their direc- 
 tion is vertical; viz., the direction in which the lubricating 
 fluid descends over the cornea. 
 
 5. Every part of the object should be excluded, except that 
 which is under immediate observation. 
 
 6. The light which illuminates the object should have a 
 very small diameter. In the day-time it should be a single 
 hole in the window shutter of a darkened room, and at night 
 an aperture placed before an Argand lamp. 
 
 7. In all cases, particularly when high powers are used, the 
 natural diameter of the illuminating light should be diminished, 
 and its intensity increased, by optical contrivances. 
 
 The following remarks by Mr. James Smith, copied from 
 the Microscopic Journal, vol. i., are recommended to the con- 
 sideration of all who are in the habit of using microscopes. 
 "Much of the beauty of the objects seen depends upon the 
 management of the light that is thrown upon or behind them ; 
 which can only be fully mastered by practice. It may be 
 remarked, however, as a general rule, that in viewing those 
 which are transparent, the plane mirror is most suitable for 
 bright daylight ; the concave for a lamp or candle, which 
 should have the bull's-eye lens, when that is used, so close to 
 it that the rays may fall nearly parallel on the mirror. If the 
 bull's-eye lens is not used, the illuminating body should not 
 be more than five or six inches from the mirror. The latter 
 
HOW TO USE THE MICROSCOPE. 53 
 
 is seldom required to be more than three inches from the 
 object, the details of which are usually best shown when the 
 rajs from the mirror fall upon it before crossing, and the 
 centre should' (especially by lamp-light) be in the axis of the 
 microscope. For obscure objects, seen by transmitted light, 
 and for outline, a full central illumination is commonly best ; 
 but for seeing delicate lines, like those on the scales of insects, 
 it should be made to fall obliquely, and in a direction at right 
 angles to the lines to be viewed. 
 
 " The diaphragm is often of great use in modifying the light, 
 and stopping such rays as would confuse the image (especially 
 with low or moderate powers), but many cases occur when the 
 effects desired are best produced by admitting the whole from 
 the mirror. 
 
 " If an achromatic condenser is employed instead of the dia- 
 phragm, its axis should correspond with that of the body ; and 
 its glasses, when adjusted to their right place, should show the 
 image of the source of artificial light, or, by day, that of a 
 cloud or window bar in the field of the microscope, while the 
 object to be viewed is in focus. 
 
 " The most pleasing light for objects in general, is that re- 
 flected from a white cloud on a sunny day ; but an Argand's 
 lamp or wax candle with the bull's-eye lens is a good substi- 
 tute. 
 
 " A large proportion of opaque objects are seen perfectly well 
 (especially by daylight) with the side-reflector, and the dark 
 box as a background ; and for showing irregularities of sur- 
 face, this lateral light is sometimes the best; but the more 
 vertical illumination of the Lieberkuhn is usually preferable, 
 the light thrown up to it from the mirror below being, with 
 good management, susceptible of much command and variety." 
 
 The management of the light with opaque objects must 
 depend in a great degree upon their size, and the manner in 
 
 5* 
 
54 THEMICROSCOPIST. 
 
 which they are mounted. If the object is small, and so mount- 
 ed as not to intercept much of the light from the mirror, the 
 mode illustrated by Fig. 16 is the best ; in other cases, that 
 shown in Fig. 15 is preferable. 
 
 The transmission of light obliquely, as near as possible at 
 right angles to the axis of vision, which is recommended in the 
 foregoing extract, for viewing delicate lines, has a very fine 
 effect, the field of view being dark, while the objects are bril- 
 liantly illuminated. The lines on the most difficult test objects, 
 as some species of Naviculae, &c., are to be seen in this manner 
 of illumination, even when otherwise invisible. For producing 
 this oblique illumination in the best manner, several ingenious 
 pieces of mechanism have been invented ; see page 42. 
 
 Next to the proper illumination of the object, the adjustment 
 of the focus is the most important thing to be attended to. 
 With a low power, the coarse adjustment is usually sufficient 
 if the workmanship be good ; but with a high power it becomes 
 necessary to resort to the more delicate arrangement of the fine 
 adjustment. Great care must be taken, however, lest the glass 
 on which the object is mounted be broken, or the object-glass 
 injured, by too sudden or too close a contact. 
 
CHAPTER V. 
 
 ON MOUNTING AND PRESERVING OBJECTS FOR 
 EXAMINATION. 
 
 IF a low power is used, and the object be one not necessary 
 to be preserved, it can be well seen if placed in the forceps or 
 on a slip of glass, but if it be desired to keep it for future 
 examination, some method of preserving it from decay, dust, 
 &c., must be resorted to ; and the method will vary according 
 to the nature of the object. 
 
 TRANSPARENT OBJECTS. 
 
 Transparent objects are mounted on slips of glass, the size 
 of which, as adopted by the Microscopic Society of London, is 
 3 inches by 1 inch, or 8 inches by 1J inches. The French 
 opticians, however, prepare many of their slides 2| inches by 
 gths of an inch, and this size is most frequently imported into 
 the United States ; indeed, a larger size is unsuitable for many 
 of the French instruments, although to be preferred on other 
 accounts. 
 
 There are three methods of mounting transparent objects. 
 1st, in the dry way in which the object is simply placed 
 upon the slip of glass, and covered with a thin glass cover, 
 cemented by its edges to the under piece, with sealing-wax 
 varnish, &c. 
 
56 THE MICEOSCOPIST. 
 
 2dly. In some preservative fluid. 
 
 3dly. In Canada balsam. 
 
 The glass slides should be clear, free from veins and bub- 
 bles, of uniform length and breadth, and should have their 
 edges ground smooth by rubbing them on a flat cast-iron plate 
 with emery and water. 
 
 Sections of teeth and bone, and of some kinds of wood, 
 hairs of animals, scales of butterflies, test objects from the 
 infusoria, &c., are best mounted dry ; but all very delicate 
 animal and vegetable tissues, to exhibit their structure clearly, 
 should not be mounted in the dry way, nor in Canada balsam, 
 but in some preservative fluid. 
 
 PRESERVING FLUIDS. A very considerable number have 
 been recommended by different observers. A mixture of salt 
 and water was used by Dr. Cook for this purpose; there is an 
 objection to it, however, owing to the development of a con- 
 fer void vegetable. 
 
 Mr. J. T. Cooper, some years since, made some experiments 
 with a view to determine the best fluid for preserving vegetable 
 colored tissues, such as some of the smaller fungi, and found 
 that salt and water, 5 grains to the ounce of water, to which 
 acetic acid had been added, answered very well. A few drops 
 of creosote or of camphor will prevent the growth of confervas. 
 
 One part alcohol to 5 of distilled water, will preserve even 
 very delicate colors. There is, however, the same objection to 
 the use of this fluid as to the salt and water. When this is used, 
 asphaltum cement may be employed for securing the thin glass 
 cover to the cell. 
 
 Pure glycerine is prepared by the London opticians as a 
 preservative fluid, and is used in the proportion of 1 part to 2 
 of water. Its oily nature, however, often causes much diffi- 
 culty in cementing the thin glass cover upon it. 
 
 A weak solution of chromic acid, one part to twenty of 
 
MOUNTING AND PRESERVING OBJECTS. 57 
 
 water is a good preserving fluid. It is also recommended for 
 hardening soft tissues, as the brain, liver, &c., for future dis- 
 section. Dr. Vanarsdale, in his introduction to the American 
 edition of Hassall's Microscopic Anatomy, speaks highly of it 
 in this respect. 
 
 One part of naphtha to seven or eight of water is said to be 
 employed by Messrs. Hett, Topping, and others, in their in- 
 jected preparations. 
 
 One part alum to sixteen of water preserves animal structures 
 for some time, though bone is injuriously affected by it. 
 
 A saturated solution of sulphate of zinc is said to preserve 
 animal tissues well, with the advantage of hardening cerebral 
 substance, but it dissolves albumen so as to cloud the liquid. 
 Mr. Straus Durkhein says it destroys all parts of caterpillars, 
 save the teguments, while the perfect insects are well preserved 
 in it. 
 
 Tulk and Henfrey state that 26 drops of creosote in a wine- 
 glassful of distilled water, preserves well, but renders the pre- 
 parations brown. 
 
 Dr. Goadby has devoted much attention to this subject, and 
 has succeeded in supplying to the microscopist a ready, cheap, 
 and effectual means for mounting animal structures with the 
 greatest possible ease and security. Dr. G. received a gold 
 medal from the Society of Arts for his invention. He has 
 kindly furnished me with the following description of his 
 different preserving fluids. 
 
 ; A 1. Bay salt (coarse sea-salt), 4 ounces, 
 Alum, 2 ounces, 
 Corrosive sublimate, 2 grains, 
 Boiling water, 1 quart. 
 
 ' A 2. Bay salt, 4 ounces, 
 Alum, 2 ounces, 
 Corrosive sublimate, 4 grains, 
 Boiling water, 2 quarts. 
 
58 THEMICROSCOPIST. 
 
 " The A 1 fluid is too strong for most purposes, and is only 
 to be employed where great astringency is required to give 
 form and support to delicate structures. 
 
 " The A 2 fluid may be very extensively used, and is best 
 adapted for permanent preparations; but neither of these fluids 
 should be used in the preservation of animals possessing any 
 carbonate of lime (all the Mollusca), as the alum becomes de- 
 composed, and the sulphate of lime is formed and precipitated, 
 and the animal spoiled. For such use the 
 
 B fluid, specific gravity 1-100. 
 
 Bay salt, 8 ounces, 
 Corrosive sublimate, 2 grains, 
 Water, 1 quart. 
 
 "Marine animals require a stronger fluid of this kind, viz., 
 specific gravity 1-148, which is made by adding more salt 
 (about 2 ounces) to the above. 
 
 "The corrosive sublimate is used to prevent vegetation grow- 
 ing in the fluid, and no greater quantity should be used than 
 2 grains per quart of fluid; but, as it coagulates albumen, it 
 must be left out when ova are to be preserved, or when it is 
 desired to maintain the transparency of certain tissues." 
 
 MOUNTING IN FLUID. 'The most minute structures, such as 
 the vessels of plants, and the muscular and other tissues of 
 animals, requiring in all cases high powers for their proper ex- 
 hibition, must of necessity be preserved in very thin cells with 
 a small amount of fluid. 
 
 On a slip of glass, 3 inches by 1, cleaned by a solution of 
 caustic potash to remove all grease, lay a drop of the fluid ; 
 put the object in this arid spread it out with the point of a 
 needle, &c. Select a thin and flat glass cover, clear it likewise 
 from grease, &c., touch its edges with cement, and drop it 
 gently over the object. Press it lightly, to exclude the excess 
 
MOUNTING AND PRESERVING OBJECTS. 59 
 
 of fluid, which can be removed by strips of blotting-paper. 
 Then cement the edges of the cover to the bottom glass. Care 
 must be taken to exclude all air- bubbles from between the 
 glasses. Objects mounted thus do not keep long, and it is 
 best to make a thicker cell. This may be made by painting a 
 round or square ring on the slip with some sort of cement 
 which will not be acted upon by the fluid employed. White 
 lead worked with 1 part linseed oil and 3 of spirits of turpen- 
 tine is well adapted for this purpose. In this ring, the fluid 
 and object are placed and the cover put on. 
 
 Pieces are also cut off the ends of glass tubes and cemented 
 on the slips with marine glue, so as to form very neat cells. A 
 square piece of glass, with a hole drilled in it, cemented on 
 the slip, forms an excellent cell. Such cells, ready prepared, 
 are imported and kept by McAllister & Co., Chestnut Street 
 above Second, Philadelphia ; together with slips, thin glass for 
 covers, mounted preparations, a good variety of instruments 
 themselves, and other things interesting or useful to the micro- 
 scopist. 
 
 Holes may be drilled in square pieces of glass, when a num- 
 ber of them are cemented together with marine glue, by means 
 of a copper tube (or drill) on a lathe, which is used with fine 
 sand or emery and water. This form of cell, as well as the 
 built-up cell, as it is called (which is a glass box, the edges of 
 whose sides are cemented with marine glue), was first contrived 
 by Dr. Goadby. 
 
 Pieces of gutta-percha tubes, cemented on to the slips by 
 heat, may sometimes be used for cells, and answer a good pur- 
 pose. Excellent cells may be made by using narrow slips of 
 glass for the sides, cementing them with marine glue: They 
 are oblong or square, and are well suited for the larger class of 
 objects. 
 
 The thin glass cell, which is made by cutting or drilling a 
 
60 THE MICROSCOPIST. 
 
 hole in a square piece of thin glass, such as is used for covers, 
 and cementing it to the slide, will be found of use in mounting 
 delicate structures. For the thicker class of objects the tube 
 cells, or those built up with strips of glass, are most suitable. 
 
 CEMENTS. 
 
 Japanners' Gold-size, or Severe Dryer, is a mixture of boiled 
 linseed oil, dry red lead, litharge, copperas, gum animi, and 
 turpentine. The first and last ingredients are its principal 
 constituents. Mr. Williams, Artists' Furnishing Store, Sixth 
 Street above Market, Philadelphia, has it for sale. 
 
 Sealing-wax Varnish consists of small pieces of sealing-wax 
 dissolved in alcohol. 
 
 A.sphaltumy dissolved in turpentine, has this advantage, 
 that spirit may be employed as the preserving fluid if desired. 
 
 Marine Glue is a mixture of shell-lac, caoutchouc, and naph- 
 tha. It is melted by heat. Caustic potash will remove its 
 traces from glass. Tulk and Henfrey give the following recipe 
 for its preparation : Dissolve 1 pound of caoutchouc in 4 gal- 
 lons of coal naphtha; 1 pint of this solution is mixed with 2 
 pounds of shell-lac; it is a most useful preparation for building 
 up glass cells, &c. Powdered gum arabic, made into a mucilage 
 with distilled vinegar, is said to be a very powerful cement. If 
 greater consistence is required a little calomel may be added. 
 
 Gum Mastich and Caoutchouc, dissolved in chloroform, is an 
 excellent cement, and has the advantage of remaining fluid at 
 ordinary temperatures, while the rapid evaporation of the 
 chloroform enables the slide to be quickly prepared. This was 
 suggested by Dr. Goddard. The caoutchouc should first be 
 dissolved in the chloroform, by the application of gentle heat, 
 to the consistence of thick mucilage, gum mastich should then 
 be added until it becomes sufficiently liquefied. 
 
MOUNTING AND PRESERVING OBJECTS. 61 
 
 A solution of Canada balsam in ether or turpentine, evapo- 
 rated to such a consistence that it can be laid on with a camel' s- 
 hair pencil, may be used like the last described, as a substitute 
 for marine glue. 
 
 Lampblack and white hard varnish, when laid on imme- 
 diately, is a good cement. Sealing-wax and white lead have 
 also been recommended. 
 
 For the thin glass covers, a mixture of the gum mastich 
 cement, above described, with asphaltum dissolved in turpen- 
 tine, will be found very suitable. Dr. G-oadby recommends for 
 the same purpose, a mixture of equal parts of gold size and 
 asphaltum dissolved in camphene. This should be applied in 
 layers, which should be isolated from each other by coating with 
 a solution of gum arabic or of marine glue dissolved in white- 
 wood naphtha. The object of this isolation is to prevent the 
 cement from penetrating between the glasses. Some very 
 valuable preparations have been ruined from this cause. 
 
 MOUNTING IN BALSAM. 
 
 Before objects are mounted in Canada balsam they should 
 be perfectly clear and free from moisture. They are commonly 
 soaked in turpentine, especially opaque objects, as it renders 
 them more transparent. Grease may be removed by sulphuric 
 ether. 
 
 Very thin and transparent objects become indistinct in bal- 
 sam ; they should be made dark. Vegetable matters may be 
 charred between two plates of glass over a lamp. Other 
 structures which cannot be charred, may be dyed by soaking 
 in a decoction of fustic or logwood, or a weak tincture of 
 iodine. 
 
 The balsam should be warmed on the slide to expel the air. 
 
 6 
 
62 THE MICROSCOPIST. 
 
 "When objects of a cellular nature have to be mounted, if they 
 are such as heat will not much injure, they may be boiled in the 
 balsam; otherwise numbers of air-bubbles will be left in the 
 cells, and the true structure cannot then be made out satisfac- 
 torily. The extra degree of heat will expand the air and 
 cause it to escape, and the balsam will take its place. 
 
 Some object of a tubular nature, such as the tracheae of 
 insects, are better seen if air be contained in the tubes; they 
 will then exhibit the spiral fibre in their interior; but a tra- 
 cheal tube filled with balsam does not show the fibre at all, the 
 balsam having made all the parts transparent. Small insects, 
 such as fleas, and the parasites of animals, when not over- 
 heated, show the ramifications of the trachea, but those which 
 have been soaked long in turpentine, or have had the air ex- 
 pelled by heat, do not exhibit the spiral markings except under 
 polarized light. 
 
 When air is to be got rid of, the heat must be high ; other- 
 wise, the use of turpentine must be avoided, the heat of the 
 balsam kept low, and the mounting accomplished quickly. 
 
 The best way to heat the balsam on the slide is to place the 
 slide on a small table made of iron or tin, to which a spirit- 
 lamp is applied, as first suggested by Dr. Goadby; yet with 
 careful management a spirit-lamp will do alone. 
 
 Some persons keep their balsam in a tin vessel that can be 
 warmed so as to melt it. A drop of the fluid can then be 
 taken out and put on the object upon the slide. This plan is 
 attended with little or no risk of air-bubbles. The cover 
 should be warmed on its under surface before it is laid on 
 the balsam, and if necessary, a small amount of heat applied 
 to the under side of the slide, to make the balsam flow more 
 rapidly. 
 
 When animal structures, such as parts of insects, or injec- 
 tions, have to be mounted, the heating of the balsam must be 
 
MOUNTING AND PRESERVING OBJECTS. 63 
 
 4*. 
 
 carefully managed, and the balsam itself be very fluid to com- 
 mence with. It should be sufficiently warmed to expel all air- 
 bubbles, and, when nearly cold, the object should be placed 
 in it and covered in the usual way. By pursuing this plan 
 (for which, with many other suggestions, I am indebted to 
 Mr. Quekett's admirable work on the Microscope), I have suc- 
 ceeded in making some excellent preparations at the expense of 
 but little time and trouble. Some operators, after covering 
 the object with balsam, if it is one that heat is likely to injure, 
 as an injected specimen, &c., leave the slide for a day or two, to 
 allow the air-bubbles to escape before putting on the glass 
 cover. But by careful management, the plan above referred 
 to will serve the purpose more readily. 
 
 If the heat applied to the slide be great, the object will be 
 sure to curl up, and bubbles will appear in all parts. It will 
 most likely be rendered useless, as no manipulation, however 
 carefully applied, will restore an overheated specimen of animal 
 structure to its former beauty. 
 
 After the slide has been prepared as above, the superfluous 
 balsam may be removed with the point of a knife previously 
 warmed in the flame of a spirit-lamp, &c. The remaining traces 
 of balsam may be removed by an old linen rag dipped in tur- 
 pentine or sulphuric ether. 
 
 MOUNTING IN THE DRY WAY. 
 
 For objects which require a high magnifying power, they 
 may be placed on a slide and covered with thin glass, whose 
 edges may be touched with cement. Objects which do not 
 require an object-glass of short focus, may be placed between 
 two slips of glass whose edges have been levelled so as to form 
 a groove, which may be filled up with cement or sealing-wax. 
 
 If the object be too thick to allow the cover to approach the 
 
64 
 
 THE MICROSCOPIST. 
 
 slide, the intervening space may be filled with paper, paste- 
 board, &c., in which a hole has been cut. Such intervening 
 substance is very useful to prevent pressure upon the object. 
 If desirable, the name of the specimen, &c., may be written on 
 this paper, especially if the cover and slide be equal in size. 
 
 MOUNTING OPAQUE OBJECTS. 
 
 These must necessarily be viewed by light reflected in some 
 manner from their surface. Some transparent objects, however, 
 may be viewed as opaque ones by using the dark well or stop, 
 e, Fig. 16. When mounted with this design they may be 
 placed on the slip of glass with a little gum-water, and sur- 
 rounded with a rim of card, paper, &c., sufficiently thick to 
 form a proper cell, which may be covered with thin glass. 
 Sometimes opaque objects are fixed on a round piece of black 
 paper stuck upon a slide. 
 
 Fig. 21. 
 
 a, Fig. 21, represents a disc of leather, felt, or other suitable 
 material, about three-eighths or half an inch in diameter, with a 
 pin passing through it. "The side for holding the object is to 
 
MOUNTING AND PRESERVING OBJECTS. 
 
 65 
 
 be blackened ; the other side is covered with white paper, on 
 which the name is written, b represents another plan, for very 
 minute objects; the pin is encased with blackened wax or 
 cement, or passes lengthwise through a small cork cylinder 
 Another method is seen at c, which consists of a small cylinder 
 of cork or felt with a pin passing transversely. These must 
 be blackened with common lacquer (shell-lac dissolved in alco- 
 hol) and lampblack, holding them over a candle to dry. 
 Sometimes these cylinders are made of ivory, with the inside 
 turned hollow like a small box ; the pin runs through them as 
 at c, and supports the object. The ivory is dyed black, and 
 the inner surface made as sombre as possible. Mr. Quekett 
 recommends to place the objects on pieces of cork glued to the 
 
 Fig. 22. 
 
 bottom, side, or cover, of small pill-boxes, as seen in Fig. 22. 
 Opaque objects should always be viewed with a black ground, 
 and the darker the object, the more sombre must be the 
 mounting. White is, of all colors, the worst which can be 
 employed, unless the object is totally black. 
 
 6* 
 
THE MICROSCOPI8T. 
 
 MOUNTING CRYSTALS FOR POLARIZED LIGHT. 
 
 These must be so enclosed that the air is completely ex- 
 cluded, otherwise a change will take place, and the objects be 
 spoiled. When it can conveniently be done, it is well to 
 mount them in Canada balsam. Sir David Brewster recom- 
 mends mixing cold-drawn castor oil with the Canada balsam. 
 In this case the edges of the thin glass cover should be ce- 
 mented, as the castor oil prevents the balsam from becoming 
 hard. 
 
 Each preparation should be properly labelled, either with a 
 writing diamond on the glass slide, or on the paper cover of the 
 slide ; and it may save trouble if this be invariably performed 
 as soon as mounted. 
 
CHAPTER VI. 
 
 ON PEOCURING OBJECTS FOR THE MICROSCOPE. 
 
 THE topic suggested by the title of this chapter is almost 
 endless; for the microscopist may claim contributions from 
 every department of natural science. The animal, vegetable, 
 and mineral kingdoms, all offer him interesting objects of in- 
 vestigation. We shall content ourselves with noticing some of 
 the most important or attractive in each department. 
 
 INORGANIC. 
 
 Agate. This form of silica is often found imperfectly crys- 
 tallized, and thin plates, prepared by the lapidary's wheel, ^th 
 of an inch thick, exhibit a rich motley coloring when viewed 
 by polarized light. 
 
 Carbonate of Lime. Small spherules of this substance are 
 sometimes found in the urinary deposits of the horse. They 
 are often composed of concentric layers; at other times the 
 fibres are radial. Illuminated by polarized light under a power 
 of 100 diameters, they are splendid objects. 
 
 Crystallization of Salts. Independently of the beautiful 
 forms assumed by different salts during their crystallization, a 
 great variety of forms may be obtained by mixing small quan- 
 tities of the different solutions in a little weak gelatine, starch, 
 mucus, &c. To procure specimens, put a drop or two of water, 
 
68 THE MICROSCOPIST. 
 
 solution of gelatine, &c., upon a slide, put into it a drop of 
 some strong solution of salts, as Epsom salts, hydrochlorate of 
 ammonia, tartaric acid, &c. Hold the slide over the spirit- 
 lamp until evaporation is perceived, when it should be removed 
 and placed under the microscope. If the evaporation is too 
 rapid, the crystals will not be well formed. They may be 
 mounted dry, or in balsam. A power of 30 diameters is 
 generally sufficient. Crystals of salts form interesting and 
 splendid objects under polarized light. 
 
 Ice. A plan for observing the crystallization of water is as 
 follows. Mix some water with a little charcoal, chalk, &c., in 
 such a manner that a number of fine particles may be mechani- 
 cally suspended in it; then take a glass slide, place it on a 
 cold night in an exposed situation, as outside of a window-sill ; 
 pour upon it as much water as it will support without running 
 over the edge, and let it remain all night. The next morning, 
 if the weather has been sufficiently cold and the atmosphere 
 dry, neither water nor ice will be seen on the slide ; but the 
 particles of charcoal will be found arranged in the various 
 forms which they assumed while the water crystallized. The 
 slide may be carefully prepared with Canada balsam for pre- 
 servation. 
 
 Crystals of Iron Pyrites and other substances ; Oolites ; and 
 various sorts of sand; are interesting objects. The sand from 
 Turkey sponge, and from the sea, often contains minute shells 
 of various kinds, as iheforaminifera, &c., corallines, and other 
 zoophytes. 
 
 .Sections of Granite, Limestone, &c., are also of considerable 
 interest ; but sections of coal, made very thin, so as to be viewed 
 by transmitted light, develope clearly its vegetable origin, and 
 are therefore of special importance. 
 
 Deut-Ioduret of Mercury. The change of color in this salt 
 is a beautiful object. If a little of it be placed in a watch- 
 
PROCURING OBJECTS. 69 
 
 glass, having another inverted over it, and then the lower one 
 heated over the flame of a spirit-lamp, the salt will be sub- 
 limed. Placed on the stage of a microscope, with a power 
 of 30 diameters adjusted to focus at the inner surface of the 
 upper glass, minute crystals will be seen to form of a bright 
 yellow color, which, as they cool, return to the original red. 
 
 VEGETABLE TISSUES. 
 
 Vegetable Tissues are prepared by tearing, making thin sec- 
 tions, maceration in water, dissection, or are examined in their 
 natural state. 
 
 The spiral, dotted, and reticular vessels of plants require 
 generally to be dissected out, which is to be done under a 
 shallow magnifier. A single lens of one inch focus will an- 
 swer very well for this purpose. Having procured a piece of 
 asparagus, or the petiole of the garden rhubarb, &c., cut out a 
 piece about an inch long, split it open with a sharp knife or 
 scalpel, examine it under the magnifier, and separate with a 
 needle-point any of the vessels you require from the surround- 
 ing cellular tissue. This process is facilitated by dropping a 
 little water on the specimen. To prevent it moving, the speci- 
 men may be fixed with beeswax during the dissection. Ves- 
 sels, ducts, and cellular tissue, when prepared, should be kept 
 in spirits of wine until mounted. 
 
 Fig. 23 represents the tissues in a longitudinal section of 
 Italian Reed j a, are cells of the pith ; b, annular ducts ; c, 
 spiral duct ; d y dotted duct ; e, woody fibre ; /, cells of the 
 integument. 
 
 Cuticles. The external covering of plants, or cuticle, con- 
 sists of a thin membrane, adherent to the cellular tissue be- 
 neath it. Under the microscope it appears traversed by lines 
 
70 
 
 THE MICROSCOPIST. 
 
 in various directions, giving its surface a reticulated appear- 
 ance. The form of these reticulations varies in different 
 
 Fig. 23. 
 
 plants : in some they are hexagonal, in others prismatic or 
 irregular. Cuticles may be mounted dry or in fluid. The 
 geranium, oleander, &c., aiford good specimens. See Fig. 40. 
 
 The cuticle of the under side of the leaf of many plants, 
 exhibits under the microscope dark spots among their reticu- 
 lations. These are called stomata, and are the orifices by 
 which a function analogous to respiration in animals is effected. 
 They also serve for the exit of water from the plant by means 
 of evaporation. Plants destitute of stomata, as the South 
 American Cacti, &c., will remain in a hot and dry atmosphere 
 without losing their moisture. The form, number, and ar- 
 rangement of the stomata vary in different plants. 
 
 Cellular Tissue is the first and most generally developed 
 
PROCURING OBJECTS. 
 
 71 
 
 simple form of vegetable life. Its primary development may 
 be seen by examining a small portion of yeast at intervals 
 under the microscope. No plant is without cellular tissue, 
 and many are destitute of any other kind of tissue, as the 
 lichens, and some fresh-water algae. A section of the pith of 
 elder, pulp of peach, &c., will afford specimens. 
 
 The petals of flowers are mostly composed of cellular tissue ; 
 their brilliant colors arise from the fluid contained within the 
 cellules. These form excellent microscopic objects, and when 
 mounted in balsam are permanent. The pelargoniums and 
 geraniums are among the most interesting. 
 
 The petal of the anagallis, or scarlet chickweed, is a beauti- 
 ful object. The spiral vessels diverging from the base, and 
 the singular little cellules which fringe the edge, are worthy of 
 notice. 
 
 Cells differ in form according to the mode in which they are 
 aggregated, a, Fig. 24, represents the dodecahedral and 
 
 Fig. 24. 
 
 dotted cells in the pith of elder. Cells are either surrounded 
 by a simple membrane, or by thickened walls. The thicken- 
 ing of the wall takes place by a deposit of woody matter on 
 the inside. Occasionally, portions of the cell-wall are left un- 
 
72 THEMICROSCOPIST. 
 
 covered by deposits, giving rise to porous cells (>, Fig. 24), or 
 dotted cells (a, Fig. 24); at other times the thickening matter 
 is in the form of a ring or spiral coil, constituting annular (c, 
 Fig. 24) and spiral cells (d, Fig. 24). 
 
 Vascular Tissue, prepared by maceration and dissection, 
 presents many interesting subjects. Spiral vessels, c, Fig. 23, 
 consist of membranous tubes with conical extremities, inter- 
 nally furnished with one or more spiral fibres. As the vessels 
 grow, the spiral fibre breaks into short pieces, forming rings. 
 The vessels are then called annular, Z>, Fig. 23. If the pieces 
 of fibre are still shorter, they are called dotted or reticulated 
 vessels, c?, Fig. 23. The root of the garden rhubarb, the 
 stem of the hyacinth, the leek, &c., furnish examples. 
 
 A peculiar form of vessel is met with in the common carrot ; 
 it is obtained from a root in a layer between the yellow central 
 portion ancl the red annulus. 
 
 Sections of Wood. These are cut thin, so as to allow them 
 to be viewed as transparent objects. Hard woods, containing 
 gum, resin, &c., should be soaked in essential oil, alcohol, 
 ether, &c., before mounting. By transverse slices, a variety 
 of beautiful lace-like objects may be obtained, but little infor- 
 mation is acquired from them of the real structure of the wood. 
 For this purpose, if the tree is of the endogenous and branch- 
 less kind which grow by additions to the interior a vertical 
 section is also necessary. If the tree be an exogen, two verti- 
 cal sections will be required in addition to a transverse one. 
 The exogens grow by annual layers exteriorly under the bark, 
 and are branched. In these one of the vertical sections should 
 be radial and the other tangental. The radial vertical section 
 will show the number and size of the medullary rays ; that is, 
 the small portions of pith which proceed horizontally from the 
 centre, enclosed in a sheath of woody fibres. The frequency 
 and size of the medullary rays determine the number and 
 
PROCURING OBJECTS. 73 
 
 strength of the branches of the tree. This section also ex- 
 hibits in coniferous trees (as the pine, &c.), the beautiful disc- 
 like glands which adhere to the woody fibres. These are 
 beautiful objects, and sometimes require a power of 200 or 300 
 diameters. The tangental vertical section is a slice across the 
 medullary rays; it exhibits the form and arrangement of the 
 cellular tissue within them. All the vertical sections show the 
 form, size, and connexion of the woody fibres ; spiral, reticu- 
 lated, and dotted vessels, &c. ; and are far more instructive than 
 the transverse sections. 
 
 Charcoal. Thin sections of charred wood are very interest- 
 ing and instructive. 
 
 Fossil Woods. Thin sections must be made by grinding on a 
 lapidary's wheel. They should be polished. 
 
 Siliceous Cuticles, &c., from equisetum, straw, cane, &c., 
 are prepared by heat in a covered crucible, or by boiling and 
 digestion in nitric acid. The most favorable example for 
 showing the form in which silica occurs in plants, is the husk 
 of the oat or wheat. If a husk of oat be examined under the 
 microscope, having been mounted in water or Canada balsam, 
 a series of bright parallel columns, serrated on each side, may 
 be observed among the cellular tissue : if another specimen be 
 burned carefully between the glasses, and the ashes be mounted 
 in balsam, the siliceous columns will still be seen. In the 
 ashes of the husk of wheat, rows of concave discs may be 
 observed, which are composed of some metallic oxide. In the 
 ashes of the calyx and pollen of the mallow, organized lime 
 may be detected. In the ashes of coal, a variety of vegetable 
 structures, as cellular tissue, spiral vessels, &c., may be dis- 
 covered. In these experiments it is necessary to render the 
 ashes transparent by immersion in balsam. 
 
 Hairs, Down, &c., from leaves and stems, are generally 
 opaque objects. In the plants which produce cotton, the hairs 
 
 7 
 
74 THEMICROSCOPIST. 
 
 are attached to and envelope the seeds. Hairs are composed 
 of cellular tissue. Their functions are said to be either lym- 
 phatic or secreting. They offer great varieties in form, some 
 being stellated, others forked or branching. The hairs of Vir- 
 ginian spiderwort (Tradescandia Virginica), the sting of the 
 Nettle (Jjrtica dioica), and the radiating scale or hair in 
 Eloeagnus, the Oleaster, are interesting specimens. 
 
 Pollen may be mounted in Canada balsam; or, if rather 
 transparent, in fluid; or dry. Sometimes the grains are inte- 
 resting opaque objects. The common form of the pollen or 
 farina of flowers is spherical, with a smooth, punctured, or 
 spiny surface; but some are square, others cylindrical, oval with 
 attenuated extremities, or triangular with convex sides. The 
 pollen of the passion flower is very curious, and if immersed 
 in very diluted sulphuric acid opens and disperses the grains. 
 The pollen of Datura stramonium, or Jamestown weed, and 
 others, when immersed in a few drops of weak acid placed 
 upon a slide under the microscope, emits a tube of some 
 length. The granular matter in the pollen may then be seen 
 to pass along the tube until the pollen is emptied. The Diameter 
 of the pollen varies considerably in different plants; among the 
 smallest are those of the Sensitive Plant. 
 
 Starch. The granules of starch (not the ordinary impure 
 starch of the laundress) obtained from different plants, are 
 found, when examined under the microscope, to differ in size 
 and form. Some are spherical, others elliptical, flask-shaped, 
 polyhedral, &c. Hence this method of examination affords a 
 ready means of detecting fraud in the substitution of one kind 
 of grain for another. Starch granules, although so very minute, 
 are composed of a fine and delicate membrane, enclosing a 
 fine mealy powder. It may be compared in some respects to a 
 common pea, in which the legumen is enclosed in a testa or 
 skin. Starch granules are not soluble in cold water, nor is 
 
PROCURING OBJECTS. 
 
 75 
 
 iodine capable of acting on them while the membrane enclos- 
 ing its contents remains whole. If the granules be triturated 
 or immersed in hot water, the membrane will be rupturecl, and 
 iodine will then turn them blue. Starch is readily separated 
 from wheat, potato, arrow-root, &c., by repeated washings in 
 cold water. To obtain it from rice, the grains should be mace- 
 rated for a few days, and to prevent the decomposition of the 
 gluten, a little soda should be added to the macerating water. 
 Under the microscope, the surface of starch-grains often appears 
 corrugated, and each of them has one or two bright spots, 
 called the hilum, which is supposed to be the part where the 
 starch adheres to the cell. See Fig. 25. a, represents starch 
 cells of the pea, showing grains of starch in the interior; 6, 
 separate grains of starch, with strise and hilum ; c, granules 
 of wheat-starch ; d, sago meal ; e } rice-starch ; /, potato- 
 
 starch ; g, isolated cells of rhubarb, containing starch-granules. 
 Under polarized light they present the beautiful phenomenon 
 of the black cross. They should be mounted dry, and protected 
 from the pressure of the upper glass by a rim of thin paper. 
 
76 
 
 THE MICROSOOPIST. 
 
 Seeds are generally opaque objects, and present a great 
 variety of beautiful and interesting forms. 
 
 Hard Tissues, the stones and shells of nuts, &c., are pre- 
 pared like bone, &c., by cutting and grinding. Some require 
 the lapidary's wheel. 
 
 Rapliides, or crystals from the interior of plants. If the 
 leaf or bulb of a common hyacinth be wounded, a discharge of 
 fluid ensues ; if this be received on a slide and submitted to 
 the microscope, a number of minute acicular bodies will be 
 observed floating in the liquid. They are called raphides. They 
 are common in many plants. Fig. 26, a. represents cells of 
 
 Fig. 26. 
 
 the beet-root, containing conglomerate raphides ; b, octohedral 
 and prismatic crystals of oxalate of lime in the cells of an 
 onion. By scraping hickory, or other bark, on to a slide, 
 moistening it with the breath, and blowing off the woody par- 
 ticles; or by placing a part of the ashes of a burnt maple leaf, 
 coat of an onion, &c., on a slide, such crystals may be seen. 
 They may be mounted dry or in balsam. 
 
 Mosses are supposed to be destitute of woody fibre and vas- 
 cular tissue. When a leaf is carefully examined, the septa 
 
PROCURING OBJECTS. 77 
 
 which divide the cells are sometimes found to take a spiral 
 course. To observe this structure, soak the moss in water, to 
 expand the cells. 
 
 It is essential, in collecting mosses, to preserve the theca or 
 seed-vessel, for without it the genera cannot be determined; 
 while this part, with the calyptra and operculum, are the most 
 valuable for the microscope. 
 
 Algae. Are interesting objects. The green, mucous, slime- 
 like matter in damp garden walks, and the hair-like weeds in 
 ditches, are examples of fresh-water algae. The sea-weeds of 
 our coast are marine algae, and are often found having zoo- 
 phytes adhering to them; they are then splendid opaque ob- 
 jects. For mounting in balsam, the smaller kinds, of a bright 
 scarlet color, are the most valuable. 
 
 ferns. The genera are mainly distinguished by the posi- 
 tion and arrangement of the organs of reproduction. These 
 are mostly on the under side, or along the margin of the leaf 
 or frond. They are best examined as opaque objects. They 
 should be collected before they are quite ripe. The spores 
 (seeds) are usually enclosed in brown capsules, each having 
 an elastic ring about its equator, which when ripe bursts, and 
 the spores are dispersed to a distance. Spores may be mounted 
 either as transparent or opaque objects. The development of 
 ferns may be observed by placing the spores in moistened 
 flannel and keeping it at a warm temperature. At first a single 
 cellule is produced, then a second, and so on. After this the 
 first cellule divides into two, and then the others, by which a 
 lateral increase takes place. 
 
 Lichens and Fungi afford interesting objects. The various 
 kinds of mildew upon vegetable substances are familiar ex- 
 amples of minute fungi. 
 
 Organic Fabrics possess much interest in a commercial 
 point of view, in addition to the curiosity arising from the 
 
 7* 
 
78 
 
 THE MICROSCOPIST. 
 
 manner in which the threads or bundles of fibres are woven or 
 interlaced. For this purpose they should be examined as 
 opaque objects on a black ground, with a magnifying power 
 of from 30 to 60 diameters. The fibres of cotton are readily 
 distinguished under the microscope from those of linen, wool, 
 &c. Cotton fibres are tubular, and are formed' of pure cellular 
 tissue. These tubes, from the thinness of their sides, often 
 collapse and appear like flat ribbons or bands. The reason 
 assigned for the preference given to linen (flax) over cotton 
 for lint, for surgical purposes, is that the fibres of the former 
 are solid cylinders of woody fibre, while the edges of the 
 flattened bands of the latter are supposed to irritate the 
 
 rig. 27. 
 
 wounds. Fig. 27 exhibits the different appearance of these 
 fibres under the microscope; a, fibres of flax; b, cotton fibres; 
 c, filaments of silk ; d, wool of sheep. 
 
 Circulation in Vegetables. The circulation in plants, termed 
 cydosis, is a revolution of the fluid contained in each cellule, 
 
PROCURING OBJECTS. 79 
 
 and is distinct from those surrounding it. It can be observed 
 in all plants in which the circulating fluid contains particles of 
 a different refractive power or intensity, and the cellules are of 
 sufficient size and transparency. Hence all lactescent plants, 
 or those having a milky juice, with the other conditions, ex- 
 hibit this phenomenon. The following aquatic plants are 
 generally transparent enough to show the circulation in every 
 part of them : Nitella ~kyalina y Nitella translucens, Chara 
 vulgaris, and Caulinia fragilis. In the Frogbit (Hydrocharis), 
 it is best seen in the scales surrounding the leaf-buds, with a 
 power between 60 and 200 diameters. 
 
 The jointed hairs of the filament of the anther in Trandes- 
 cantia Virginica (Spiderwort) ; the delicate hairs on the leaf- 
 stalk of Senecio vulgaris (Groundsel) ; and a section of the 
 leaf of Vallisneria spiraliSj will show the circulation, especially 
 when viewed with a high power. 
 
 For the following recapitulatory list of plants, which may be 
 used in microscopic examinations, the author is indebted to 
 Balfour's Class Book of Botany, Edinburg, 1852. 
 
 1. Cells and Cellular Tissue. Sea-weeds; rice-paper; inde- 
 pendent cells with nuclei, in yeast plant (Torula Cerevisias) ; 
 cells with nuclei and nucleoli in ripe fruit of strawberry, in the 
 onion bulb, and in ovules or very young seeds; cells united in 
 a linear series in common mould, conferva, and many hairs ; 
 branching cells in many hairs, and in some moulds, as 
 Botrytis; cells united in fours in pollen of Acacia, and in some 
 species of sea-weeds ; cells thickened by deposit of lignin, in the 
 shell of the Cocoanut, and Attalea funifera or Piacaba palm, in 
 the stone of the peach, cherry, and nut, in the seed of the 
 Ivory palm and Date, in the gritty matter of the Pear; cells 
 with siliceous covering in Diatomacese. Porous cells in Elder 
 pith, in stem of common garden Balsam (Balsamina horten- 
 sis), in the outer covering of the seeds of Gourd and Almond, 
 
80 THE MICROSCOPIST. 
 
 in the wing of the seed of Lophospermum erubescens, and in 
 Calempelis scaber. Spiral cells in leaves and stems of many 
 orchids, as Onicidium and Pleurothallis ruscifolia, in garden 
 Balsam, in the leaf of Sphagnum, the fructification of Liver- 
 worts, the winged seed of Sphenogyne speciosa. Annular cells 
 in Opuntia. Filamentous cells in Mushrooms and Agarics. 
 Hexagonal cells in pith of Elder. Stellate cells in Rush. 
 Ciliated moving cells in Vaucheria, Fuci, and Chara. Professor 
 F. Schulze states, that by means of nitric acid and phosphate 
 of potash, the cells of plants, young or old, hard or soft, may 
 be perfectly isolated for microscopic examination. 
 
 2. Vessels and Vascular Tissue. Woody tissue in the stem 
 of ordinary trees ; the fibres may be separated by maceration 
 from the inner bark of the Hemp-plant, Flax-plant, New Zea- 
 land Flax, Mallows, &c., Disc-bearing woody tissue in Scotch 
 Fir, Weymouth Pine, Araucaria, Altingia excelsa, Cycas, 
 Winter's bark tree, Illicium. Dotted vessels in stem of Willow, 
 Sugar-cane, Pitcher- plant. Spiral vessels in Oncidium bicolor, 
 Banana, and Plantain ; most liliaceous plants (as Hyacinth, 
 Lily, and Crinum), leaf of Geranium and Strawberry, Cabbage, 
 Lettuce, Asparagus shoot; branched spirals in Long-kek and 
 Anagallis. Annular vessels in Opuntia vulgaris, Leek, Equise- 
 tuml Telmateia. Reticulated vessels in garden Balsam. Sca- 
 lariform vessels in Tree Ferns, Diplazium seramporense, As- 
 plenium pubescens, Osmunda. Lactiferous vessels in various 
 species of Ficus, as the India-rubber fig (Ficus elastica), Gutta- 
 percha plant (Isonandra Gutta), Euphorbias, Lettuce, Dande- 
 lion, Celandine, Goatsbeard. 
 
 3. Contents of Cells. Starch-cells in Potato, angular starch- 
 granules in Rice, compound starch- granules in Arrow-root, 
 peculiar starch-grains in the milky juice of Euphorbia. Air- 
 cells and lacunae in the Rush, Sparganium ramosum, Lim- 
 nocharis plumieri, and other aquatic plants. Cells with 
 
PROCURING OBJECTS. 81 
 
 raphides of oxalate of lime in Rhubarb root, cells with aeieular 
 crystals in Hyacinth, cells with octohedral and prismatic crys- 
 tals in Onion and Squill. Oil-cells in rind of Orange and 
 Lemon, in leaves of Hypericum, and of the Myrtle order. 
 Chlorophyll cells in Mosses, Vallisneria, Chara; cells with 
 coloring matter in leaf of Rottlera tinctoria, and in petals. 
 
 ANIMAL TISSUES, ETC. 
 
 INFUSORIA. These minute animals, some of which are 
 only the 2 smooth P ar ^ f an i Qcn lu diameter, are extremely 
 numerous. Between 700 and 800 different species have 
 been discovered and described. Dr. Ehrenberg, to whom we 
 are indebted for much of our knowledge respecting the ani- 
 malculse, divides them into two classes, i. e., Polygastrica and 
 Rotatoria. The first class is so named from their possessing a 
 digestive apparatus composed of many globular vesicles, which 
 perform the functions of stomachs. The Rotatoria are so 
 called from their possessing rotary organs about their mouth. 
 These are much more highly organized than the others. The 
 Polygastrica increase by self-division, or by the growth of 
 gemmules or buds upon their bodies ; the Rotatoria are herma- 
 phrodite, and oviparous. Many animalculce are loricated; or 
 protected by a shell, or shield, which is generally siliceous : 
 others are destitute of such an appendage. 
 
 The following table exhibits the families or groups into 
 which this interesting department of animal life has been di- 
 vided by Ehrenberg. Those who wish further information re- 
 specting them are referred to his work "Die Infusionsthier- 
 chen," or to Pritchard's "History of Infusoria, Living and 
 Fossil." Dr. Mantell's work on Animalcules contains also 
 much valuable information. 
 
82 
 
 THE M I C R O S C P I S T. 
 
 CLASS I. POLYGASTRICA. 
 
 1 
 
 
 
 
 Self- ( 
 
 division > 
 complete. 1 
 
 illoricated or shell-less, 
 loricated or shelled, 
 
 Monadina. 
 Cryptomonadina. 
 
 1 
 
 Body 
 
 destitute of 
 appendages. 
 (No foot-like ' 
 processes.) 
 Gymnica. 
 
 Form < 
 of body 
 
 Selfdivi- 
 sion in- 
 complete, 
 
 formed in 
 clusters. 
 
 ' self- dividing on all ( 
 sides (globular), j 
 
 Volvocina. 
 
 , Vibriona. 
 Closterina. 
 
 1 
 
 
 f ,'i i ,^,: , .,,*.., i 
 
 
 Dinobryina. 
 
 
 8 
 
 1 
 
 Foot-like processes 
 variable. 
 Pseudo-poda. 
 
 C compound foot-like process 
 < i.-,, + A j from one aperture, 
 j lo "cated, ^ gimple foot-like process from 
 L 1 one or from each aperture, 
 
 Amoebaea. 
 Arcellina. 
 
 Bacillaria. 
 
 1 
 
 Hairy 
 
 ( illoricated, 
 
 Cyclinida. 
 
 "^ 
 
 'One receiving and 
 
 f 
 
 xeridinaea. 
 
 1 
 
 discharging orifice 
 only for nutrition. 
 
 j illoricated, 
 1 loricated, ...... 
 
 Vorticellina. 
 Ophrydina. 
 
 ? 
 
 Anopisthia, ^ 
 
 3 
 
 Two ditto orifices, f 
 
 
 
 k 
 
 illon 
 
 n 4-^/1 
 
 
 Enchelia 
 
 | 
 
 one at eacu 
 extremity. 
 
 \ loricated, 
 
 Colepina. 
 
 "3 
 . 
 
 Enantritena. 
 
 i 
 
 
 a<; ',*. 
 
 
 1 
 
 Orifices situated 
 
 f C mouth furnished with pro- 
 l illoricated,^ boscis, tail absent, 
 
 Trachelina. 
 
 
 ^77 ? U . e ' 
 
 
 1 
 
 1 moi 
 
 ith anterior, tail present, 
 
 Ophryocercina. 
 
 1 
 
 ' eta ' (.loricated, " - - - - - - 
 
 Aspidiscina. 
 
 1 
 
 Orifices abdominal. 
 Catotreta. 
 
 ^ illor 
 ( loric 
 
 , , ( locomotive organs cilii, 
 catecl, do do Tarioug 
 
 _A p J 
 
 Kolpodea. 
 Oxytrichina. 
 E up lota. 
 
 
 
 CLASS II. 
 
 ROTATORIA. 
 
 
 wifv. o c,;mwio f margin of cilii-wreath entire. ( illoricated, Icthydina. 
 Tinuous th of " 1 BbWrocfta. j loricated, Oecistina. 
 cilH ' f < mar e in of * li thlobed or^. noricated5MeKalotrochaea- 
 
 (Jfonofrocfta.) 
 
 
 
 ScJiizotra 
 
 cM. 1 loricated ' 
 
 Floscularia. 
 
 (with the cilii-wreath divided into( M 1n _; / , oto j TT^ati . 
 several series. \ lloricated, Hydatmea 
 
 Polytrocha. ^loricated, Luchlanidota. 
 
 (Sortl^cha ) \ With tbe dl iwo r s e e a ries diVided Int ^ "l^icated, Philodinaea. 
 rit : s - ^loricated, Brachionaea. 
 
PROCURING OBJECTS. 83 
 
 In reference to obtaining infusoria, some persons imagine 
 that if they procure a portion of fetid ditch-water, or take 
 a few flowers, &c., and macerate them in water, they will be 
 furnished in a few days with all the varieties they may desire ; 
 but this is not the case. Infusoria will of course be found, 
 but they will be only of the most ordinary kinds. To obtain 
 those of higher interest, some degree of skill is required. 
 Many remarkable species have been taken in meadow-trenches 
 in the slowly running water, after a summer shower, especially 
 about the time that the first crop of hay was mown. Among 
 healthy water-plants, the various kinds of Vorticellina (Sten- 
 tors and Vorticellsej or trumpet and bell-shaped infusoria), and 
 Rotatoria (wheel-animalcules), may be sought for with success. 
 The stems of aquatic plants have often the appearance, to the 
 naked eye, of being encased with mouldiness, or rancor, which 
 on being examined with the microscope, proves to be an ex- 
 tensive colony of arborescent animalcules. The dust-like 
 stratum sometimes seen on the surface of ponds, and the 
 shining film which sometimes covers water-plants, assuming 
 various hues of red, brown, yellow, green, and blue, is caused 
 by the presence of infusoria, some of which are very beautiful. 
 Many species live in the clean fresh water of rivers, lakes, and 
 springs; and the brine of the ocean, Imewise, as well as the 
 mould on the surface of the earth, has its microscopic inhabi- 
 tants. 
 
 In order to procure animalculse, provide yourself with a 
 number of clean, wide-mouthed, glass phials, fitted with proper 
 corks, not glass stoppers, so that the air may have access to 
 them, at least to some extent. Have also a rod, or walking- 
 cane, which may be prepared with a spring-hook and ferule for 
 fastening a phial on its end, although a piece of twine is a 
 good substitute. On reaching the pond, &c., carry the phial 
 (attached to the rod) in an inverted position, and when at 
 
84 THE MICROSCOPIST. 
 
 proper depth, or in the neighborhood of water-plants, it should 
 be turned quickly, when animalculae, &c., will run into it. 
 Water-fleas and Daphnise should be frightened away by shak- 
 ing the phial before turning. If in the phial, they go quickly 
 to the bottom, and the upper water can be poured off. Exa- 
 mine the water with a pocket lens, and preserve the animal- 
 culse. 
 
 The indications of the presence of infusoria are specks mov- 
 ing about in the water, or an apparent mouldiness around the 
 stalks of the water-plants, &c., which may have been caught 
 in the phial. If these appearances be not discerned by the 
 magnifier, the water may be thrown away, and another place 
 resorted to. A small portion only of vegetable matter should 
 be preserved in the phial, as its decay may soon kill the ani- 
 malcules. 
 
 Small newts and many larvas should be preserved; the for- 
 mer especially, as they eat up the Daphniae, Monoculi, &c., 
 that destroy the Vorticellse. In the branchiae of young newts, 
 too, and in their feet, the circulation of the blood is beautifully 
 seen. 
 
 The phial should sometimes be laid horizontally on the bot- 
 tom of the pond, and scrape the surface of the mud. This 
 should be put in a large jar with water, and in a day or two 
 the animalculae will be on the surface of the mud, from which 
 they can be removed with the fishing-tubes (see page 49), and 
 placed under the microscope. 
 
 If the creatures are too minute to be seen easily with the 
 naked eye, pour a little water from the vessel containing them 
 into a watch glass, and place it on a piece of card-board, ren- 
 dered half black and half white. The white ground will make 
 the dark specimens apparent and vice versa. They can then 
 be seen with the pocket lens, and taken out with the fishing- 
 tubes. 
 
PROCURING OBJECTS. 85 
 
 In order to show the stomachs, cilia, &c., of animalcule 
 under the microscope, rub some pure sap-green or carmine on 
 a palette or plate of glass, and add a few drops of water. If 
 the glass 'be now held on one side, a portion of the coloring 
 matter may be put into the water on the slide containing the 
 animalculse. If they be vorticellse or rotiferse, the particles of 
 coloring matter will show the vibratile actions of the cilia, 
 whilst other particles swallowed by the animals, will give a 
 rich tint to the compartments of their alimentary canal. 
 
 Fossil Infusoria. A great number of infusorial earths may 
 be mounted in balsam (test objects dry, however) without 
 washing, &c., but others must be repeatedly washed or digested 
 in acid. For the skeletons or shields in carbonate of lime, 
 consisting mostly of Polythalamia, or many-chambered shells, 
 Professor Ehrenberg has directed to place a drop of water on the 
 slide, and put into it as much scraped chalk as will cover the 
 fine point of a knife, spreading it out, and leaving it to rest a 
 few seconds; then withdraw the finest particles, which are 
 suspended in the water, together with most of the water, and let 
 the remainder become perfectly dry. Cover this with Canada 
 balsam, and hold it over a lamp until it becomes slightly fluid 
 without froth. 
 
 Siliceous Shields of Infusoria, such as those in guano, 
 Richmond earth, &c., require to be well washed and boiled or 
 digested in nitric or hydrochloric acid. After this, a small 
 quantity of the sediment in which they are contained should 
 be placed on a number of slides, and those containing the best 
 specimens laid aside for mounting. In guano and Richmond 
 earth are found most beautiful saucer-shaped shells, having 
 hexagonal markings, which have received the name of Cosci- 
 nodiscus, or sieve-like disc. They vary in size from T <jth to 
 y^Qjjth of an inch in diameter. 
 
 The polishing slate of Bilin, which is found in strata fourteen 
 
 8 
 
86 THE MICROSCOPIST. 
 
 feet thick, consists almost entirely of the siliceous shells of 
 Infusoria, so small that forty thousand millions are contained 
 in a single cubic inch. 
 
 The eatable earth of Sweden and Lapland is likewise com- 
 posed mostly of such shells. A layer of this earth occurs in 
 the province of Luneberg, Saxony, which is twenty-eight feet 
 thick. It contains a beautiful species of minute, oval, figured 
 shell called the Campilodiscus. 
 
 Sponges. These lowly-organized bodies are found both in 
 salt and fresh water in all parts of the globe. Many of them 
 are very minute, and may be examined without much prepa- 
 ration, but others require to be burned, or acted on by acid, 
 to show the small masses of flint, called spicula, which form 
 their rudimentary skeleton, as well as other masses of the 
 same material, which enter largely into the framework of the 
 young sponges or gemumles. 
 
 Corals are best examined by horizontal and vertical sec- 
 tions. If the animal matter only is required, the sections may 
 be macerated in hydrochloric acid, to which five or six times 
 its bulk of water has been added. 
 
 Zoophytes. Besidents at the sea-side, or occasional visitors, 
 when provided with a microscope, have frequent opportunities 
 of examining some of these most elegant of animal forms. 
 Scarcely a piece of sea-weed or a fragment of shell will be 
 found, that does not afford a habitation for some member 
 of this interesting family. The animals are generally found 
 in clusters or compound ; sometimes communicating at a com- 
 mon centre; at other times distinct and only connected by 
 the solid matter of which their polypidoms are formed. Some 
 few, as the common fresh-water polype, do not secrete any 
 hard substance either around or within them. 
 
 INSECTS. These afford the most numerous and beautiful 
 
PROCURING OBJECTS. 87 
 
 objects for examination, as there is scarcely a part of the body 
 of an insect that does not exhibit some remarkable structure. 
 
 Antennae. The horns of insects not only vary in form in 
 different genera, but in the male and female of the same 
 species. They may be mounted as opaque, or in Canada 
 balsam. 
 
 Eggs. The eggs of insects are generally of an oval form, 
 the outer covering being sufficiently rigid to resist ordinary 
 external impressions ; others are, however, soft and pliant. In 
 some species they are globose, as in many Lepidoptera ; or 
 conical, as in the large white cabbage-butterfly; cylindrical, 
 pear-shaped, barrel-shaped, &c. They are for the most part 
 smooth ; but many are very beautiful, ornamented with symme- 
 trical ridges, canals, dots, &c., giving them, as Reaumer ob- 
 served, the appearance of embossed buttons. Some are fur- 
 nished with appendages for peculiar purposes. Thus the eggs 
 of the dung-fly (Scatophaga putris) has two oblique props at 
 one end, to prevent it sinking too deep in the matter upon 
 which it is deposited, while those of the water-scorpion (Nepa 
 cinerea) are furnished with a coronet of spines, forming a re- 
 ceptacle for the egg which is deposited immediately after- 
 wards. Sometimes, one end of the egg is provided with a 
 sort of cap or lid; at other times the egg is in one piece, and 
 the enclosed larva must gnaw or burst through it. The color 
 is very various, although white, yellow, and green are the 
 most prevalent tints. 
 
 In many species the eggs are deposited singly ; in others, 
 they are discharged en masse. Some arrange them symme- 
 trically, and others enclose them in a mass of gluten, espe- 
 cially those whose larvae inhabit the water. Many species em- 
 ploy a gummy matter to attach them firmly to the substances 
 on which they are placed ; while some, as the yellow-tail moth 
 (Arctia chrysorrhaea), wrap them in a coating of down, which 
 
88 THE MICROSCOPIST. 
 
 they pull off their own bodies; and the lackey moth (Lasio- 
 campa Neustria), deposits her eggs in a spiral coil round the 
 stems of fruit trees. 
 
 Most varieties require to be viewed as opaque objects under 
 a power of 30 to 60 diameters. 
 
 Elytrcij or wing-cases of insects, are often singularly en- 
 graved and colored, and form the most brilliant of all opaque 
 objects. Some are covered with beautiful iridescent scales, 
 and others are furnished with branched hairs. Some of them 
 are much improved by being mounted in a thick cell with 
 Canada balsam, while others lose much of their splendor by 
 being so treated. In order to ascertain whether an elytron 
 will be improved by the balsam, one of the legs, or some part 
 supplied with a few of the iridescent scales, should be touched 
 with turpentine ; if the brilliancy be increased, it may be 
 mounted in balsam, if otherwise, dry. The elytra of some 
 beetles, after having been softened in caustic potash, may be 
 mounted between flat glasses, as ordinary objects. 
 
 Eyes of Insects, Arachnida, &c. The structure, number, 
 and form of the eyes of insects may be ranked among the 
 most curious parts of natural history. *They are generally 
 hemispherical, on each side of the head, but sometimes they 
 are oval or kidney-shaped. When closely examined, they are 
 found to consist of a vast number of minute lenses, generally 
 hexagonal, but sometimes quadrangular or circular. In the 
 ant there are 50 of such lenses in each eye ; in the common 
 house-fly 4000 ; in the dragon-fly 12,500 ; and, according to 
 Geoffrey, in the eye of a butterfly 34,650. When one of the 
 eyes is detached from the head and cleaned, the lenses are 
 found to be as clear as crystal. If a cluster of eyes be placed 
 under the microscope, at a distance without its focus equal to 
 their focal length, the lens of each eye will exhibit a distinct 
 image of a candle, &c. ; placed before it. 
 
PROCURING OBJECTS. 59 
 
 The external form of the eye may be seen in situ in all in- 
 sects when viewed as opaque objects, but the layer of lenses 
 requires the aid of maceration and dissection to free them 
 from a considerable amount of pigment. They may then be 
 mounted dry, in fluid, or in balsam. If required to be flat, 
 they must be made so by pressure while soft, otherwise they 
 are liable to split. 
 
 If the eye of a fly, or other insect, properly prepared by 
 mounting in balsam, be held near the eye of an observer who 
 looks through it at a distant candle, &c., the interference of 
 light in the minute lenses will cause a number of images to be 
 perceived, tinged with beautiful colors. 
 
 The eyes of spiders are single. They have from four to 
 twelve, variously arranged. Some insects have also single 
 eyes in addition to the compound eyes before noticed. 
 
 Feet. The structure of the feet of those insects which sup- 
 port themselves on polished surfaces, and against the force of 
 gravity, is very remarkable, and it is doubtful if it be yet per- 
 fectly understood. Some suppose them to act as suction-pads, 
 others that they secrete a viscid fluid by means of which they 
 stick with sumcient force to enable them to walk. The latter 
 theory is rendered most probable by microscopic researches. 
 
 The number of pads on each foot is variable. 
 
 The anterior and middle pairs of feet of the male Dytiscus 
 are furnished with curious disc or cup-shaped appendages on 
 the inside of the leg. They may be viewed as opaque and in 
 balsam. 
 
 Hairs of Insects, &c., may be mounted dry, in fluid, or in 
 balsam. In some spiders the hairs are branched; in the larvae 
 of many insects they are covered with spines, as the hairs of 
 caterpillars, &c. ; and in the Crustacea they are provided with 
 spines, or plumed like a feather. The hairs and scales of in- 
 sects will be further treated of in the chapter on Test Objects. 
 
90 THE MICROSCOPIST. 
 
 Heads, Mouths, &c. The manducatory apparatus of insects 
 is a subject of great interest to the entomologist. The divi- 
 sion of insects into Mandibulata and Haustellata are founded 
 thereon; the first having jaws, the latter a proboscis or suck- 
 ing instrument. Some of them require but little preparation, 
 and may be mounted as opaque objects; others, as the pro- 
 bosces and lancets of flies and bees, demand considerable skill 
 to display them to the best advantage. When thin and trans- 
 parent, they should be mounted in fluid, but if thick and opaque, 
 in balsam. Before mounting in the latter way, they should be 
 dissected while soft, and laid out on a slide to dry. 
 
 Parasitic Insects should be placed in spirit and water in 
 order to kill them. They may be mounted in fluid or balsam. 
 Some of the large kinds may be examined as opaque objects. 
 The term Epizoa has been applied to them because occurring 
 on the exterior, in contradistinction to those occurring within 
 animals, which are called Entozoa. Some of them are classed 
 with insects, as having six legs ; while others, having eight, are 
 called Acari, and are included in the class Arachnida. 
 
 Some very minute insects, called Aphides, are abundant on 
 plants, the leaves, &c., of which they destroy. Others, called 
 Cynips, are the cause of the excrescences on the leaves, &c., 
 of trees, termed galls. The well-known oak-apple is produced 
 by the Cynips quercus, which is a most elegant object when 
 examined by reflected light. The same may also be said of 
 the insect from the gall of the rose. Gather the galls when 
 ripe, and place them in a box covered with gauze. In a few 
 days or weeks numbers of insects will escape from the gall, 
 and those exhibiting beautiful colors may be selected. 
 
 Among the Acari, may be mentioned the cheese-mite, A. 
 domesticusj and the itch-insect, A. scabiei. To obtain the 
 latter, the operator must examine carefully th,e parts surround- 
 ing each pustule, and he will generally find in the early stage 
 
PROCURING OBJECTS. 91 
 
 of the disease, a red spot or line communicating with it ; this 
 part, and not the pustule, must be probed, and the insect, if 
 present, be turned out. It is often, however, difficult to de- 
 tect its haunts. 
 
 To obtain the Entozoon fotticulorum, which is a parasite 
 occurring in the sebaceous follicles of the skin of the forehead, 
 nose, &c., squeeze the neighborhood of the little black spot 
 or pustule, so as to force out the sebaceous or oily matter. 
 This should be laid on a slide, and a small quantity of oil 
 added to separate the insects from the nidus in which they are 
 imbedded. They may then be transferred by a pencil-brush 
 to a clean slide, covered with thin glass, and mounted. 
 
 Another species of Acarus, the harvest-bug or tick, A. au- 
 tumnalisj is a very painful source of irritation to the skin 
 wherein they may have insinuated themselves. They may be 
 dislodged with a needle, and mounted in fluid or balsam. 
 
 Tracheae, and Spiracles of Insects. The respiratory system 
 of insects will be described in the chapter on Dissections, to- 
 gether with their nervous, digestive, and circulatory systems. 
 The manner of mounting them has been described. 
 
 StingSj Ovipositors, &c., frequently require considerable care 
 in dissection. They may be mounted in fluid or balsam. In 
 order to prepare them, the abdomen should be laid open by a 
 slit along the back of the insect, in order to obtain a view of 
 the relations of the various parts ; then the posterior segment 
 should be fixed to a loaded cork under water and dissected be- 
 neath a shallow magnifier. The dissection should be made 
 from right to left, proceeding from without towards the interior, 
 as far as the median line, when it should be continued from 
 within outwards. This mode of dissection may also be advan- 
 tageously employed to display or procure other objects of inte- 
 rest. See the chapter on Dissecting Objects. 
 
 SHELLS OF MOLLUSCA. The structure of shell has only 
 
92 THE MICROSCOPIST. 
 
 lately attracted the attention of inicroscopists, but since the 
 year 1842 the subject has been scientifically investigated by 
 Mr. Bowerbank and Dr. Carpenter. According to the experi- 
 ments of the latter gentleman, undertaken at the request and 
 expense of the British Association, the calcareous matter in 
 all shells is nearly equally crystaline in its aggregation, and 
 the particular forms which their fracture presents are deter- 
 mined chiefly, though not entirely, by the arrangement of the 
 animal basis of the shell, which possesses a more or less highly- 
 organized structure. 
 
 All thin sections of recent shell are translucent, except 
 when the coloring matter is opaque, or when the calcareous 
 matter is deposited in a chalky state between the true laminae 
 of the shell, as in the oyster. 
 
 Dr. Carpenter classifies shells, into 1. Prismatic cellular 
 structure, as exemplified in the Pinnce. 2. Membranous shell 
 substance, as the My a, Anatina^ and Thracia. 3. Nacreous 
 or pearl structure, as the inner surface of some species of Ostrea 
 and Mytilus. 4. Tubular structure, as the outer layer of Ano- 
 mia Ephippium, Lima scabra, &c. In some cases the tubes 
 run at a distance from each other obliquely through the shell, 
 as in Area Noce. 5. Cancellated structure. Examples of this 
 latter division, which somewhat resemble the cancelli of bone, 
 are only met with in certain fossil shells. 
 
 Shell should be examined microscopically in three ways : by 
 reflected, transmitted, and polarized light. For the first, frag- 
 ments of shell will suffice; for the others, thin sections, cut 
 both vertically and transversely, are necessary. To exhibit the 
 animal basis of shell, specimens may be treated in the manner 
 recommended for coral. 
 
 SCALES OF FISH. M. Agassiz has arranged the class of 
 fishes into four orders, according to the structure of their 
 covering, as follows : 
 
PROCURING OBJECTS. 93 
 
 Enamelled Scales. 
 
 1. Placoidians. Cartilaginous fishes, having prickly or flat- 
 tened spines, as the skates, dog-fish, and sharks. 
 
 2. Gandidians. With angular scales composed of horny or 
 bony plates covered with enamel, as the sturgeon, and bony 
 pike. Fifty out of sixty genera are extinct. 
 
 Scales not Enamelled. 
 
 3. Cteno'idians. Scales notched or serrated on their posterior 
 free edges, as the perch. 
 
 4. Cycloid fishes, with smooth scales, more or less circular, 
 and laminated, as the herring, salmon, &c. 
 
 Among the various kinds of fish-scales selected for micro- 
 scopic objects, those of the eel are much prized, as it was for- 
 merly considered that it had no scales. They may be obtained 
 from the under surface of the skin with a knife or a pair of 
 forceps. 
 
 Some scales when viewed by polarized light have a brilliant 
 effect. They may be mounted in balsam. Fossil scales, as well 
 as others, may be examined as opaque objects. 
 
 HAIR or ANIMALS, ETC. Hairs are composed of an aggre- 
 gation of epithelium cells, and the color depends upon the 
 quantity of pigment deposited in or about each cell. They may 
 therefore be called elongated developments of the epidermis. A 
 transverse section is not always round, but may be oval, flat- 
 tened, or reniform. Henle has shown that the curling of hair 
 depends upon its form, and that the flatter the hair the 
 more it curls, the flat side being directed towards the curve 
 described. P. A. Browne, Esq., of Philadelphia, has attempted 
 to show a specific difference in the races of men from the shape 
 of the transverse sections of their hair, but we think without 
 success. It is not likely that scientific investigation will ever 
 
94 THE MICEOSCOPIST. 
 
 overthrow the assertion of Scripture, " God hatli made of one 
 blood all nations of men." 
 
 Care should be taken to select both the hair and the wool 
 from each animal, as they differ materially in their structure ; 
 the finer kind, or what is known as wool, being endued with 
 the property termed felting, which property is of considerable 
 importance in a manufacturing point of view. The felting 
 property is owing to the imbricated scales on the outside of each 
 hair. In the adult human hair this structure is not very 
 apparent, but may frequently be seen in fine specimens from 
 very young infants. These, however, should not be mounted 
 in balsam. 
 
 The smaller kind of hair may be mounted dry or in fluid; 
 or, if of a dark color, in balsam. Horizontal and vertical 
 sections should be made of large hairs and spines, which may 
 be done after gluing a number together, in the same way that 
 sections of wood, &c., are made. 
 
 Sections of horns, hoofs, quills, whalebone, spines of echini, 
 &c. ; are all interesting objects. 
 
 ANATOMICAL OBJECTS AND PREPARATIONS. 
 
 BLOOD. To examine this vital fluid, it is necessary to place 
 upon a glass slide a small drop recently taken, and cover it 
 with a thin glass or piece of mica. The blood-corpuscles may 
 also be preserved in Dr. Goadby's A 2 fluid, or prepared by 
 drying rapidly on the slide and covering with the thinnest 
 glass. 
 
 The red corpuscles in man are of a circular flattened form. 
 If water be added to them, they become spherical by endos- 
 mose. Their appearance varies as they are viewed a little in 
 or out of the focus of the microscope ; in one place showing a 
 
PROCURING OBJECTS. 95 
 
 nucleus or spot in the centre, and in the other a thickened 
 edge, like a ring (a, Fig. 28). In all air-breathing, oviparous, 
 vertebrated animals, the blood-corpuscles are oval, and a nu- 
 cleus may be observed within each of them. This nucleus is 
 rendered very distinct by the addition of a drop of diluted acetic 
 acid. 
 
 The observations of Professor Owen on the blood-discs of 
 the Siren acertina, b, Fig. 28, show that the nucleus consists 
 of a cluster of nucleoli enclosed in a capsule in the centre of 
 the oval blood-disc. The length of the disc in the Siren is 
 ^Jflth of an inch, while the diameter of human blood-discs 
 average -3^ 0th of an inch. 
 
 Fig. 28. 
 
 Very frequently, under the microscope, the blood-corpuscles 
 unite by their flat surfaces, so as to form rows, like piles of 
 coin ; the disposition to which is proportionate to the quantity 
 of fibrin in the blood. 
 
 When the corpuscles are observed in a drop of blood spread 
 out between two plates of thin glass, they will often be seen to 
 present a tuberculated or mulberry appearance, which is sup- 
 posed by Donne to depend upon commencing desiccation, and to 
 arise from deficiency of serum. Others ascribe it to evapora- 
 tion from the edge of the slide. In many of my own observa- 
 
96 THE MICROSCOPIST. 
 
 tions the globules presented a compound appearance, consisting 
 of several granules, one in the centre, with the others disposed 
 around it ; the regularity of which appearance seems to intimate 
 its connexion with the structure of the corpuscle. 
 
 Circulation of Blood may be seen in the web of a frog's foot 
 (see page 47) ; in the fin or tail of a fish ; and in the legs, &c., 
 of many spiders and insects, especially aquatic larvae. There 
 is nothing so wonderful and pleasing as the sight of the blood- 
 corpuscle coursing through the vessels in the web of a frog's foot, 
 when seen with a power of about 200 diameters. The re- 
 searches of Kaltenbrunner, a distinguished German patholo- 
 gist, on the circulation of blood in a frog's foot, and the influence 
 of various irritants upon it, as seen under the microscope, have 
 added much to our knowledge respecting congestion and in- 
 flammation, and are of the highest interest to the practitioner 
 and student of medicine. They are referred to by Dr. Watson 
 in his preliminary lectures on the Practice of Medicine, and 
 their importance clearly shown. 
 
 Hassal remarks, that the circulation of blood is seen to the 
 greatest advantage in the tongue of a frog. For this purpose the 
 frog should be secured by a bandage to a thin flat piece of cork, 
 &c., which is perforated at one extremity by a square aperture. To 
 this aperture the mouth of the frog should be secured, and the 
 soft, pulp-like tongue being drawn out by a pair of forceps, and 
 spread out over the aperture, may be retained in position by pins. 
 The piece of cork (answering instead of the frog-plate) should 
 . then be fastened to the stage of the microscope. 
 
 In the view of this structure, we have displayed in action 
 various parts of the animal organization ; arteries, veins, nerves, 
 muscular tissue, epithelial cells, and glands. [Microscopic A?ia- 
 tomy.~\ 
 
 BONE should be cut into thin sections, about ^th of an inch 
 in thickness. They can be cut with a fine saw, such as are 
 
PROCURING OBJECTS. 
 
 97 
 
 made of watch-spring. They should then be cemented on a 
 piece of glass ; filed to the proper thinness ; ground upon a 
 hone } and polished by a leather strap or piece of cloth charged 
 with putty powder (oxide of tin and lead), or carbonate of iron 
 (rouge). They may be mounted dry or in balsam. Both 
 transverse and longitudinal sections should be made. 
 
 The sections may be cleaned from grease by soaking in sul- 
 phuric ether. 
 
 The bloodvessels of bone when injected are rendered more 
 conspicuous if the earthy parts of the bone are removed by 
 means of an acid. They may then be kept in oil of turpentine, 
 which renders the tissue more transparent. 
 
 Fig. 29. 
 
 When animal tissues are consolidated by the deposition of 
 earthy matter within their cells and fibres, a hard, solid sub- 
 stance is produced. Sometimes the earthy matter crystallizes, 
 as in the teeth at other times it combines chemically with 
 the gelatine of the cells, as in bone. This deposition in bone 
 
 9 
 
98 THE MICROSCOPIST. 
 
 does not occur in all the cells, as the bone requires to grow 
 and be nourished; hence arises its peculiarity of structure. 
 Independently of its hollows, or cancelli, the hard part of 
 the bone is traversed by canals, called Haversian, which run 
 in the direction of the laminae ; these are connected by trans- 
 verse communications. In a thin transverse section of bone, 
 the solid matter may be observed arranged around the Haver- 
 sian canals in concentric rows (Fig. 29). Among these layers 
 dark specks are dispersed. These dark specks (called lacunse, 
 or corpuscles of Parkinje), when magnified about 200 diameters, 
 are observed to be cavities of an irregular, oval form, from 
 which emanate numerous minute branch canals. These cavi- 
 ties appear dark for the same reason as a minute air-bubble 
 does in Canada balsam, namely, the difference of refraction 
 of the two media. By means of these branches (canaliculi), 
 lacunae, and Haversian canals, the bone is nourished with 
 proper fluids. 
 
 It has been shown by Mr. J. Quekett, that there are diffe- 
 rences in the form and size of the lacunae, in the various classes 
 of animals, sufficiently characteristic to allow of the assignment 
 of minute fragments of bone, with the aid of the microscope, 
 to their proper class. The lacunae of reptiles are distinguish- 
 able by their large size, and long oval form ; and those of fish, 
 by their angular form and the fewness of their radiating cana- 
 liculi. The lacunae of the bird may be distinguished from 
 those of the mammal, partly by their smaller size, but chiefly 
 by the remarkable tortuosity of their canaliculi. It is worthy 
 of remark, also, that the sizes of the lacunae in the four classes 
 of vertebrata, bear a close relation to the sizes of their blood- 
 corpuscles. 
 
 SECTIONS or TEETH may be made in the same way as bone. 
 Some should be soaked in hydrochloric acid, to destroy the 
 earthy matter, and others in caustic potash, to get rid of animal 
 
PROCURING OBJECTS. 99 
 
 matter. These should be mounted in fluid, the others dry, or 
 in balsam. 
 
 A tooth consists of three distinct structures, the relative pro- 
 portions and arrangement of which constitute the chief differ- 
 ences in the teeth of various animals. 1. Enamel. This is 
 crystallized phosphate of lime, deposited in the form of long 
 prisms each about 39*00^ ^ an ^ ncn i diameter, produced in 
 animal cells which are almost obliterated when the tooth is 
 fully formed. In human teeth a coating of enamel is formed 
 over the crown of each. In the teeth of some animals the 
 enamel is disposed in vertical layers among the other struc- 
 tures of the tooth. This is especially the case with the grind- 
 ing teeth of large herbivorous animals. 2. Dentine, or Ivory. 
 This forms the principal substance of which the teeth are com- 
 posed. The amount of animal gelatine in it is often very 
 considerable. The earthy matter is usually deposited in the 
 form of fine branching cylindrical tubuli, radiating from the 
 centre of the tooth. These tubules have been successfully 
 injected with coloring matter by soaking the tooth in a solution 
 of Saunder's wood, &c. On the ends of the dentine tubuli are 
 placed the ends of the enamel prisms, in the human tooth. 
 Dentine is now established by Professor Owen as an ossification 
 of the pulp of the tooth. 3. The bone or Cementum, of 
 teeth, is composed of a mass of earthy matter and cartilage, 
 having minute cavities or bone-corpuscles and calcigerous 
 canals. 
 
 Sometimes a vertical section is made of a tooth in situ, ex- 
 hibiting a section of the jaw with its cavities for the nerves 
 and vessels, as also the manner in which the alveolar process 
 which forms the socket is constructed. Both vertical and trans- 
 verse sections should be made. 
 
 SKIN. The skin is supplied with a very rich capillary 
 network ; and also provided with two or more sets of glands, 
 one for secreting the perspiratory fluid, the other an unctuous 
 
100 THE MICROSCOPIST. 
 
 or sebaceous matter for lubricating the skin itself. Taking 
 the human skin as an example, we should commence the study 
 with vertical sections, made through parts supplied both with 
 hair and papillae. The perspiratory glands are best seen in the 
 soles of the feet, and palms of the hands ; the sebaceous glands 
 should be examined in parts about the face or chest, where 
 hairs are numerous; these latter sections will also show the 
 roots of the hairs and the hair follicles. The skin may be ren- 
 dered firm enough for vertical section by hardening in a satu- 
 rated solution of carbonate of potash or in strong nitric acid. 
 
 The epidermis may be separated by maceration in water, or 
 by plunging the skin into water nearly boiling hot. Great 
 care must be taken in separating it in order to see the coacal 
 prolongations sent by it to line the sebaceous crypts, bulbs of 
 the hairs, &c. 
 
 The capillary network of the cutis vera may be seen in in- 
 jected specimens when the cuticle has been removed, which will 
 often require the aid of maceration for the purpose. If the 
 skin be that of a black man, care should be taken in the removal 
 of the cuticle, as in it may be examined the rete mucosunij or 
 colored layer, which consists of a series of minute hexagonal 
 cells, containing pigment. The same structure may be seen 
 in the skins of animals whose hairs are black ; for this purpose 
 the lips of a black kitten, when injected, should be selected, 
 as in them the mode of growth of the young whiskers, their 
 copious supply of bloodvessels and nerves, and various other 
 points of interest, may be observed. The papillae are best 
 shown in the extremities of the fingers and toes, when inject- 
 ed ; the cuticle which invests them should also be mounted as 
 an object, with its attached or papillary surface uppermost, as 
 in this the grooves for their lodgment, together with the open- 
 ings of the sudoriferous glands, can be well seen. 
 
 The two layers of integument in insects, &c. ? may be sepa- 
 
PROCURING OBJECTS. 101 
 
 rated mechanically, or by maceration in dilute hydrochloric 
 acid. 
 
 EYES. Many objects of interest may be obtained from the 
 eyes of various animals ; as the crystalline lens, the pigment, 
 the ciliary processes, the retina, and the membrane of Jacob. 
 The structure of the crystalline lens in fish is best seen after 
 the lens itself has been hardened by drying, boiling, or long 
 maceration in spirit. After having peeled off the outside, the 
 more dense interior will be found to split up into concentric 
 laminae, and each lamina will also be found to be composed of 
 an aggregation of toothed fibres; these are best seen when 
 mounted in fluid, but if dyed, they will show very well in 
 balsam. The pigment is easily obtained by opening a fresh 
 eye under water. It may then be detached as a separate layer, 
 and parts of it floated on slides to dry, after which they may 
 be mounted in balsam. The ciliary processes are best seen 
 when injected; they should be mounted in a convenient cell 
 with fluid, and viewed as opaque objects. The retina should 
 be examined from a very fresh eye, between glasses, and a 
 little serum or aqueous humor added, to allow the parts to 
 be well displayed ; but water must be avoided, as the nervous 
 matter will be considerably altered by it; the membrane of 
 Jacob will also require the same precautions, but the vascular 
 layer of the retina, when injected, may be well seen after 
 having been dried. 
 
 For the dissection of the eye, the plaster mould, described in 
 the chapter on Dissecting Objects, will be found useful. The 
 eye may be fixed to the plaster by bent pins while it is yet 
 fluid, as otherwise it would not remain firm. Sometimes the 
 eye is frozen, to facilitate dissection. 
 
 MUSCULAR FIBRE. Muscles are of two kinds, voluntary 
 and involuntary ; from their functions. The voluntary muscles 
 of all the vertebrata, and the articulate animals (as insects, 
 
 9* 
 
102 THE MICEOSCOPIST. 
 
 &c.), have their fibres marked with transverse striae. The in- 
 voluntary muscles are not so marked. These marks are sup- 
 posed to point out the ultimate corpuscles or cells of which 
 the fibrillae are composed. The general opinion is, that the 
 juxtaposition of cells is the true form of the ultimate fibre. 
 Several microscopists, however, of some note, believe the fibre 
 to be spiral, and enclosed in a membranous sheath. Others 
 have thought the transverae striae to be due to a corrugation 
 of the fibre. In my own examinations I have met with cases 
 where the structure appeared to be a bead-like fibre wound 
 spirally into a tube, or around a central unmarked fibre ; yet 
 other observations, especially with polarized light,, show a lon- 
 gitudinal arrangement of cells. Perhaps the true structure is 
 a compound of both these modes; the sheath being spiral, and 
 the ultimate fibre longitudinal. If we should state that the 
 ultimate granules or cells of muscular substance are arranged 
 in fibres, and that a number of such fibrillae are enclosed in a 
 spirally corrugated sheath, a number of such bundles being 
 united together ; the description would correspond with the 
 majority of observations. 
 
 A small portion of muscle, freed from cellular tissue, may 
 be put on a slide with some kind of fluid, placed under the dis- 
 secting microscope, and the fibres torn asunder with fine needles. 
 It should be preserved in fluid under a thin glass cover. 
 
 The nerves of muscle may be displayed in a thin layer of 
 delicate fibres which form a part of the abdominal wall of a 
 frog, by employing a compressorium. The capillary blood- 
 vessels may be seen when injected. By the use of the com- 
 pressor, the thin recti muscles of the eyes of small birds, if 
 seen soon after death, will, without injection, show both nerves 
 and capillaries. 
 
 NERVE. The dissection of nerves, to show their ultimate 
 structure, is similar to that of muscle, above described. It 
 
PROCUEING OBJECTS. 103 
 
 should be performed, however, in a little serum or white of an 
 egg; as water, &c., changes its appearance. As soon as the 
 true structure has been well seen, water, ether, &c., may be 
 added, to show how much they change its original appearance. 
 In all examinations of nerve or muscle, the more delicate the 
 structure, the sooner after death should it be dissected. Dr. 
 Stilling recommends to place the spinal cord in weak spirit for 
 twenty-four hours, after which it may be successfully steeped 
 in stronger spirit, before sections are made. He directs the 
 sections to be made with a razor whose surface is moistened 
 with alcohol. 
 
 FIBROUS AND AREOLAR TISSUE. Nearly allied to involun- 
 tary muscular fibre is a fibrous tissue termed the yellow or 
 elastic; this is often found in connexion with another, finer 
 and less elastic, and called, from its color, the white fibrous 
 tissue; a mixture of the two is known to anatomists as the 
 areolar tissue, and is largely used in the animal economy, 
 as it forms a support for all the vessels, nerves, and muscles, 
 from either of which it may be easily procured. The yellow 
 tissue is found in nearly an isolated condition in the ligamen- 
 tum nuchge of the necks of some animals, especially of the 
 ruminating tribe ; it also enters largely into the formation of 
 the intervertebral discs. A portion of the ligament from the 
 neck of a sheep or calf, even after boiling, will exhibit the 
 elastic fibres exceedingly well ; they are of nearly uniform size, 
 generally curled at their extremities, and of a yellowish color. 
 They may be prepared as muscle or nerve, with the needle 
 points. 
 
 CARTILAGE. Consists of cells, contained in cavities which 
 are formed in a solid and hyaline intercellular substance. 
 (Fig. 41). In fibro-cartilage, instead of homogeneous intercel- 
 lular substance we meet with elastic fibres. The structure is 
 easily examined by making thin sections. 
 
104 THE MICROSCOPIST. 
 
 If any of the above tissues are to be kept, they should be 
 mounted in fluid, as spirit and water, or the creasote liquid. 
 
 Mucous AND SEROUS MEMBRANE. Mucous membrane is 
 the investment of all the internal parts of the body, continu- 
 ous with the skin. Every cavity, organ, or gland, which 
 opens on the surface, is lined by it. Shut sacs are lined by 
 serous membrane. 
 
 These membranes may be divided into two parts : the 
 epithelium, and the basement membrane. The external skin 
 is evidently a similar structure, somewhat modified, and is 
 capable, under certain circumstances, of taking on a similar 
 function. The epithelium of skin is the cuticle or epidermis, 
 but the basement membrane, though present, is not easily 
 shown, except where the surface is raised into papillae. 
 
 The epithelium exists in three varieties : the scaly, prismatic, 
 and spheroidal. * The first kind is most largely developed in 
 the skin'; the cuticle, with its horns, hairs, hoofs, and feathers, 
 &c., is made up of it. Detached scales may be obtained from 
 the inner side of the mouth or by scraping any of the serous 
 membranes gently with a knife. The prismatic ; or according 
 to Dr. Todd, the columnar ; is abundant throughout the stomach 
 and intestines, and even the lungs. Each prism is attached by 
 its sides to its fellows, and endwise to the basement membrane. 
 The attached extremity is generally pointed, the free one wide 
 and flat, and covered with vibratile cilia, which may be often 
 observed in rapid motion, some time after the death of the 
 animal. The third variety, or spheroidal, is to be met with in 
 all glandular structures, as the tubes of the stomach and kidney, 
 and the secreting structure of the liver. 
 
 The basement membrane is structureless, and is not supplied 
 in any way with vessels. The best places for viewing it are 
 the tubes of the kidney and stomach, and the villi of the small 
 intestine. It is supported upon a submucous areolar tissue, in 
 
PROCURING OBJECTS. 105 
 
 which both the bloodvessels and nerves ramify, but do not in 
 any case enter the membrane itself. 
 
 In order to examine the surface of mucous membranes, the 
 mucus should be washed off as gently as possible, by a small 
 stream of water or a small syringe. If the epithelium be re- 
 quired, it may be detached from the surface with a scalpel, 
 placed on a glass slide, and viewed as a transparent object, with 
 a power of 200 diameters. The mucous membrane itself may 
 be seen by reflected light while under water ; a movable dis- 
 secting microscope being brought over it. In order to obtain 
 a correct idea of the external surface, sections, both horizontal 
 and vertical, should be taken and submitted to high powers. 
 When the membrane cannot be%ell cut into thin slices, it may 
 be separated with the needles, or by slight pressure in the 
 compressorium. Where epithelium is so abundant as to form 
 a layer of cuticle, it must be removed by maceration, in order 
 to see the mucous surface. 
 
 The arrangement of the capillaries, as seen in the injected 
 mucous membranes, is exceedingly interesting and forms a nu- 
 merous class of preparations. 
 
 CILIARY MOVEMENT. If the roof of the mouth of a living 
 frog be scraped with the end of a scalpel, and the detached 
 mucous matter placed on a glass slide, and examined with a 
 power of 200 diameters, the epithelium cells, and the move- 
 ment of their cilia, may be well seen. The most common 
 method is, however, to cut off with a pair of fine scissors a small 
 portion of the gills (branchiae) of an oyster or mussel ; lay it on 
 a slide or on a tablet of an animalcule cage, with a drop or two 
 of the fluid from the shell. With the needle-points separate 
 the filaments from each other, and cover it lightly with a thin 
 piece of glass. The cilia may then be seen in several rows, 
 beating and lashing the water with amazing activity. If fresh 
 water be added instead of that from the shell, the movement 
 
106 THE MICROSCOPIST. 
 
 will speedily stop. The motion and structure of the cilia is 
 sometimes better observed after the lapse of some hours, as the 
 movement will then have become sluggish. 
 
 Sometimes the ciliary movement may be witnessed on 
 epithelial scales found in the mucus taken from the nasal pas- 
 sages during a slight catarrh. 
 
 INJECTED PREPARATIONS. For the mode of making these 
 preparations, the reader will refer to the chapter on Minute 
 Injections. 
 
 There can be no doubt but that the blood is, par excellence, 
 the vital fluid. From it is derived the material for the develop- 
 ment of each part of the organization ; nerve as well as muscle, 
 bone, tendon, &c. Even unnatural and morbid growths must 
 have their origin in some alteration in this all-pervading, all- 
 sustaining fluid. " The life thereof is the blood thereof." 
 
 The capillary vessels of the body form the vehicle of vital 
 distribution and stimulus. By them is conveyed the nutrition 
 of all the tissues ; and through them all foreign substances are 
 extracted, and the blood thus rendered pure and vital. By 
 endosmotic action through their thin coats in the lungs, oxy- 
 gen unites with the carbon, and probably the iron of the blood, 
 and carbonic acid gas is expelled; and from their peculiar ar- 
 rangement in the kidney, lobules of the liver, &c., effete mat- 
 ters are strained, as it were, from the circulation, and carried 
 off. 
 
 But there is another function, of equal, if not superior, im- 
 portance with those just mentioned, which, in the judgment of 
 the author of this work, the capillaries are destined to subserve. 
 They are, doubtless, the cause, perhaps the sole cause, of the 
 difference in the sensations experienced in the various organs 
 and tissues of the animal frame, under the stimulus of the 
 varied excitants to which the organization is subject in health 
 and disease. The nervous cords may transmit impressions to 
 
PROCURING OBJECTS. 107 
 
 the sensorium, but it is the stimulus of the blood the vital 
 fluid variously modified by the capillaries, which determines 
 the character of those impressions. Hence we find that those 
 parts which are but slightly supplied with capillary vessels are 
 comparatively dull of sensation, and vice versa. How other- 
 wise can we account for the different sensations produced by 
 inflammation in different tissues ? as for instance, the burning, 
 pungent pain of inflamed skin, contrasted with the dull, aching 
 sensation of inflammation in the fibrous tissue. 
 
 May not the peculiar and delicate arrangements of the capil- 
 laries in the different coats of the eye; the ear; the papillae 
 of the skin ; and other organs of special sense, be referred to 
 the same design ? 
 
 Other physiological facts also tend to establish this view. 
 " If the abdominal aorta be tied, the muscles of the lower 
 extremities will be paralysed, and on removing the ligature, 
 and allowing the blood to flow, the muscles will recover them- 
 selves." (Todd and Bowman.} We know, too, that the 
 stimulus of too much, or too rapid, blood on the brain, will pro- 
 duce delirium, and illusions of special sense : impressions being 
 made on the sensorium independent of the action of usual ex- 
 ternal stimuli. 
 
 The theory above referred to, in order to explain or account 
 for these phenomena, may be expressed as follows : The prin- 
 ciple of life, or the capacity for vital action, is a property im- 
 pressed by the Great Creator upon the material organization 
 of both animals and vegetables. In addition to this, the pro- 
 perties of sensation and volition have been imparted to all ani- 
 mals. These properties point out the existence of a spiritual 
 being or entity (distinct from vital organization), which holds 
 its connexion with each part of the animal frame by means of 
 the nervous system. It is, however, essential to the integrity 
 of this connexion, and to the proper performance of the func- 
 
108 THE MICROSCOriST. 
 
 tions of volition and sensation, that the nerves should be sup- 
 plied with the proper vital stimulus of the organization the 
 blood and the mode in which this stimulus is supplied, will 
 determine the character of the impressions made upon, or 
 received by, the entity or being referred to. 
 
 This entity, which some have confounded with the vital 
 principle, acts through the nerves in a manner peculiar to itself. 
 The force or material by which it holds connexion with the 
 bodily frame is not electricity, although in some respects its 
 properties are analogous. Messrs. Todd and Bowman present 
 the following arguments, which prove conclusively the last re- 
 mark. They show that the electric fluid could not be suffi- 
 ciently insulated in the minute nerve-tubes to enable them to 
 be proper conductors that the most delicate tests of electricity 
 fail to discover it, when applied to nerve in action that a 
 ligature to a nerve stops the propagation of nervous power, but 
 not of electricity that if a piece of nerve be cut out and be 
 replaced by an electric conductor, electricity will be transmit- 
 ted when applied, but no nervous force excited by stimulus 
 above the section will pass to the parts below and that both 
 nerve and muscle are infinitely worse conductors of electricity 
 than copper or other metals. These facts are clearly opposed 
 to the present popular theory of the identity of nervous force 
 and electricity. 
 
 More extended remarks upon our theory of the cause of 
 sensations would be out of place in a work of this kind ; yet as 
 the varied shapes and arrangement of the capillaries must be 
 demonstrated by means of the microscope, and as we have 
 seen no theory which attempts to explain the design of such 
 variations, an allusion to this seemed to be appropriate-. 
 
 Hassall, in his Microscopic Anatomy, records an instance of 
 the capillary circulation being maintained for hours in a muti- 
 lated portion of a frog's tongue, which had been entirely sepa- 
 
PROCURING OBJECTS. 109 
 
 rated from the rest. A similar instance came under the 
 author's own observation, in a thin slice from the kidney of a 
 mouse, which had been dead for some hours. An account of 
 it was published in the Philadelphia Medical Examiner for 
 December, 1851, pp. 767-770. 
 
 The frontispiece represents some of the forms in which the 
 capillaries are arranged. Fig. 1, represents the injected capil- 
 laries of muscular tissue, after Gerber, and a preparation of the 
 author's. 
 
 Fig. 2. Injected lobules of adipose tissue, from the skin of 
 a pigeon : the lower part of the figure shows a portion of the 
 same, magnified 200 diameters, from Quekett's Histology. 
 
 Fig. 3, is a vertical section of the injected skin of a dog's 
 foot, showing the vessels of the sensitive papillae, and of the 
 adipose tissue beneath. From an injection by Topping, in the 
 author's possession. 
 
 Fig. 4, exhibits a small piece of injected mucous membrane, 
 from the small intestine of man. The villi appear to lie flat, 
 on account of the preparation being mounted in balsam and 
 covered with thin glass. This is one of the most beautiful of 
 the author's preparations. Not only are the villi well injected, 
 but a conglomeration of flask-like creca, or glands, are well seen, 
 having the minute vessels which ramify upon their sides exhibited. 
 
 Fig. 5, is from a specimen of injected liver, by Topping. 
 
 Fig. 6, represents the capillary vessels which ramify among 
 the air-cells (sections of bronchial tubes ?) in the human lung. 
 
 Fig. 7. Injected papillae of the tongue. 
 
 Fig. 8. Injected ciliary processes of the eye. 
 
 Fig. 9. Injected Malpighian bodies from the kidney. 
 
 Fig. 10. The muscular coat of the small intestine, from 
 Gerber, after Lieberkiihn. 
 
 Figures 11 and 12, represent the most common modes of termi- 
 nation of the arteries, either looped or branching after Q-erber. 
 
 10 
 
CHAPTER VII. 
 
 TEST OBJECTS. 
 
 THE discovery of this class of objects by Dr. Goring, a full 
 account of which may be found in Mr. Pritchard's works on 
 the Microscope, was the chief cause of the modern improve- 
 ments in the achromatic compound microscope. 
 
 Mr. Pritchard, following Dr. Goring, divides test objects 
 into two classes, viz., tests of the penetrating power, and tests 
 of the denning power of the instrument ; the first showing its 
 destitution of spherical and chromatic aberration, and mechani- 
 cal imperfection; and the other class showing its angle of 
 aperture. 
 
 This distinction is not now necessary, as few persons, save 
 those engaged in the manufacture of object-glasses, attend to 
 the former, the improvement in achromatic object-glasses hav- 
 ing been so extensive that a good instrument, in this respect, 
 is readily procurable. Still, it may be well to give an outline 
 of the means by which the presence or absence of achromati- 
 city may be known. 
 
 Chromatic aberration is rendered sensible by almost any 
 transparent object, when the light falls upon it obliquely; but 
 more especially by such as are not transparent, but only illu- 
 minated by intercepted light, of which a very good example 
 may be seen in a piece of fine wire sieve, treated like a dia- 
 phanous object, also in a thin plate of metal perforated by very 
 small holes. The various colors are seen according to the 
 
TEST OBJECTS. Ill 
 
 order of their refrangibility, by putting the object both within 
 and without the focus, as well as by viewing it at the focal point 
 
 Spherical aberration is most sensibly felt in viewing opaque 
 objects, especially if of the brilliant class. It shows itself in 
 a variety of ways : first, as a diffused nebulosity over the whole 
 field of view; secondly, as a confined nebulosity, extending 
 only to a certain distance from the object; and thirdly, in a 
 want of sharpness and decision in the outline caused by a 
 penumbra or double image, which can never be made to lap 
 perfectly over the stronger or true one. Destitution of spheri- 
 cal aberration is evinced by the absence of these appearances, 
 and by the vanishing of the image immediately that the object 
 is put out of focus either way. 
 
 To ascertain the defects alluded to above, a minute globule 
 of mercury on a black ground, known as an " artificial star," 
 is used. It presents a very minute point of light. Very mi- 
 nute globules of mercury, spread over a blackened surface, are 
 viewed as opaque objects, being illuminated by the light from 
 a window or lamp thrown on them by a condensing lens. 
 When one of these globules is in the focus of a single lens 
 object-glass, a strong coma surrounds the miniature image of 
 the window seen in the globule, and when within or without 
 the focus, the light of the window swells out into a circular 
 disc. These appearances are more or less accompanied by 
 prismatic colors. 
 
 When an achromatic combination, perfectly corrected for 
 both kinds of aberration, is employed, the globule should ex- 
 hibit similar appearances both within and without the best 
 focus; and when at the focus, the point of light should be seen 
 as a minute disc, free from irradiations and color, except a 
 general blueness, which results from the irrationality of the 
 spectra of the different glasses of which the object-glass is 
 composed. 
 
112 THE MICROSCOPIST. 
 
 Power of definition depends, in a great measure, upon the 
 angle of aperture of the object-glass. A deficiency of angular 
 aperture is shown by a want of light, producing unsatisfactory 
 vision, which is rather increased than ameliorated by augment- 
 ing the intensity of the artificial illumination ; by an incapa- 
 city of showing lined objects, except such as are of the lowest 
 class ; and by giving very large spurious discs with artificial 
 stars; also by showing easy test objects with the lines faint, 
 while the spaces between them are darker and more opaque 
 than they ought to be. 
 
 When the aberrations are properly corrected; and the angle 
 of aperture considerable, the lines on test objects become fine, 
 sharp, and dark, and the spaces between them bright, pro- 
 vided the illumination has. been properly conducted; they 
 moreover become visible in a very faint light; the outline and 
 the lines are seen at once; and the spurious discs of all bril- 
 liant points are very sharp and small. 
 
 In order to explain more fully what is meant by angular 
 aperture, let A and a, Figs. 30 and 31, represent two objects, 
 in all respects alike ; and suppose B, B, and 5, b, to be two 
 object-glasses of equal focal length ; the former a single lens, 
 of the best construction, such as was used in the old compound 
 microscope, and the latter a lens of the newest form, termed 
 an achromatic. Now these object-glasses will form their re- 
 spective images at I and i, and they will be of equal dimen- 
 sions. But if the number of rays proceeding from A and 
 falling upon the single lens B, B, is not enough, when col- 
 lected at I, sufficiently to stimulate the eye, any minute pore, 
 stria, or other marking at A, will not be rendered visible ; 
 while from the increase of aperture in 6, 6, allowing much 
 more light to be transmitted, every mark at a, will be repre- 
 sented at i t and the eye being powerfully acted on by the 
 increase of light, will be highly sensible of it. 
 
TEST OBJECTS. 
 
 113 
 
 The angles B, A, B, and b, a, b, are the angles of aperture 
 of the respective object-glasses, and the quantity of light 
 transmitted will be as the squares of B, B, and b } 6, their focal 
 length being equal. 
 
 Fig. 30. 
 
 Fig. 31. 
 
 It may be supposed, that if we throw more light upon an 
 object, so that more may be collected by the object-glass, we 
 shall be better able to define its structure ; and this would 
 probably be the case if we could throw light only upon those 
 minute parts which we wish to examine, and not upon the 
 whole object, but as we cannot increase the relative propor- 
 tions of light, the advantages proposed cannot be derived. 
 
 10* 
 
114 THE MICROSCOPIST. 
 
 In examining test objects it will be well to remember that 
 there are generally some very easy ones, even among samples 
 of the most difficult kind. The darker the specimen, the more 
 easily is it made out ; and the more transparent the tissue, the^ 
 greater difficulty there is in developing its structure. Great 
 attention too should be paid to the proper illumination of the 
 object, or a superior instrument will be undervalued. 
 
 The following list affords an account of those objects most 
 frequently used as tests of the defining power of the instru- 
 ment. 
 
 BAT'S HAIR. This is a most beautiful structure, presenting 
 a series of scale-like projections arranged in the form of a 
 whorl around the central part or shaft. They are least nume- 
 rous at the base of the hair, and increase towards the apex. 
 
 MOUSE HAIR differs materially from the other in size and 
 structure. Their internal structure is cellular, there being 
 three or more rows of cells in each hair, the color of the hair 
 depending on the pigment within the cells. Under the micro- 
 scope all hairs should have their light or transparent parts 
 clearly and distinctly separated from the darker portions, and 
 it is from the sharpness with which the parts are separated 
 that a correct opinion of the value of an instrument can be 
 obtained. 
 
 In selecting hair of animals for examination, the lightest 
 colored should be preferred. Like the scales on insects, the 
 hair from different parts of the same individual varies consi- 
 derably in structure. 
 
 HAIR OF THE DERMESTES. This very remarkable hair is 
 obtained from the larva of a small beetle, which preys on dried 
 animal substances, as bacon and hams. It is covered with 
 brownish hairs, the longest of which are selected. 
 
 The shaft of this hair is covered with whorls of close-set 
 spines, and at the head is invested with a curious arrangement, 
 
TEST OBJECTS. 115 
 
 consisting of several large filaments or spines, which are 
 pointed at their distal extremities, and provided with a pro- 
 tuberance at their proximal ends. 
 
 This object, with the others above noticed, is a good test of 
 the defining power of a half-inch object-glass. 
 
 SCALES OP INSECTS. The dust on the wings and bodies of 
 butterflies, moths, and other insects, prove, on microscopic ex- 
 amination, to be scales or feathers, overlapping each other like 
 the shingles on the roof of a house. They vary much in form 
 and size ; and from the difficulty of developing their structure, 
 they form excellent test objects. In the present list the most 
 easy are first named. 
 
 Lepisma Saccharina. These silvery-scaled insects frequent 
 closets, book-shelves, &c., and are very common. Their scales 
 are very pretty objects, but are so easily made out as hardly to 
 deserve the name of test objects. The longitudinal striae 
 appear to stand out in bold relief, like the ribs of a shell. A 
 good glass should show well the contrast between the striae and 
 the interspaces. 
 
 Morplio Menelaus, The pale blue scales from the upper 
 surface of the wing of this splendid butterfly form a good test 
 for the half-inch object-glass, which should show clearly the 
 transverse as well as the longitudinal striae, giving it a brickwork 
 appearance. If the scale be flat, which is not common, the 
 striae should be seen over the whole surface. Sometimes the 
 scales are damaged, the pigment having been removed ; in such 
 cases the cross striae cannot be seen. The pigment, under 
 very high powers, exhibits a dotted appearance between the 
 striae. 
 
 Tinea Vestianella, or Clothes Moth. The scales of these in- 
 sects are very delicate, and require some tact in the manage- 
 ment of the illumination to resolve their lines distinctly. The 
 small scales from the under side of the wing should be taken ; 
 the others are easy. 
 
116 THE MICROSCOPIST. 
 
 Pontia Brassica, or Common Callage Butterfly. The pale, 
 slender, double-headed feathers, having brush-like appendages 
 at their insertion, are good test objects. The specimens which 
 are easily resolved are short, broad, and more opaque. The 
 striae are longitudinal, and with a power of 500 diameters 
 appear to be composed of rows of little squares or beads. 
 
 Podura plumbea. or Lead-Colored Springtail. The body 
 and legs of this tiny creature are covered with scales of great 
 delicacy. The surface of each, under a power of 500 diameters, 
 appears covered with numbers of delicate wedge-shaped dots 
 or scales, .arranged so as to form both longitudinal and trans- 
 verse wavy markings. A very small scale is a good test of the 
 defining power of a one-twelfth or one-sixteenth inch object- 
 glass. The small scales may easily be rubbed off the scale to 
 be examined, unless great care be taken in mounting, &c., and, 
 of course, it will be useless as a test object. 
 
 SHELLS OF INFUSORIA. Several delicate species serve as 
 test objects. The so-called longitudinal and transverse striae 
 are resolved by superior instruments into dots or bead-like pro- 
 jections from the surface. The Navicula hippocampusj JV". 
 angulata, N. Spencerii, &c., have been recommended as tests. 
 A species marked Navicula attenuata, is a good object, re- 
 quiring delicate illumination under a high power, in order to 
 show the longitudinal striae or dots. Several kinds of Tripoli 
 may also be used for the purpose. 
 
 For examining the striae on infusorial shells it is often very 
 necessary to have an oblique illumination. 
 
 As it is always a tedious matter with the use of a high power 
 to find a minute object on the slide under the stage, it will be 
 most convenient to bring it first into the centre of the field by 
 the use of a lower power, and afterwards substitute the high 
 power object-glass. 
 
 ARTIFICIAL OBJECTS. M. Robert, a Konigsberg optician, 
 
TEST OBJECTS. 117 
 
 has prepared glass plates, on which are ruled, with a diamond, 
 systems of a hundred lines, which, 10 by 10, approach closer to- 
 gether, according to a certain standard. Ordinary instruments 
 make out the 6th and 7th systems as separate lines. Superior 
 instruments reach the 8th and 9th. No instrument has yet 
 unfolded the 10th system of lines. This is certainly a great 
 triumph of art. 
 
CHAPTER VIII. 
 
 ON DISSECTING OBJECTS FOR THE MICROSCOPE. 
 
 REFERENCE has already been made in Chapter V. to the 
 manner of dissecting and preparing certain animal and vegeta- 
 ble tissues, yet much has been omitted, which may perhaps be 
 more fully appreciated under the present head. 
 
 The instruments required in microscopic dissections, or mi- 
 nute anatomy, are various kinds of forceps, scissors, scalpels, 
 needles, troughs, loaded corks, and arm-rests. 
 
 The forceps, in addition to the ordinary forceps used in 
 coarse or rough dissection, may be made with closely-fitting, 
 sharp points. The scissors are similar to those used for surgi- 
 cal purposes. It is useful to have a pair with the point of one 
 of its blades blunt and truncated, for cutting open tubular 
 parts, as the alimentary canal. Scissors with curved blades 
 are also of service. A pair of very small scissors, whose 
 
 Fig. 32.. 
 
 blades are kept open by a spring, a, Fig. 32, was much used by 
 Swammerdam in his dissections. One of the handles is attached 
 
DISSECTING OBJECTS. 
 
 119 
 
 to a piece of wood, b ; the other is curved as at c, in order 
 to be pressed upon by the thumb or forefinger in the act of 
 cutting. 
 
 The Microtome of M. Straus-Durekheim is constructed on a 
 similar principle, but more simple in form. Its appearance is 
 somewhat like the common shears, used for shearing sheep; 
 the cutting blades being kept apart by their union in the handle, 
 the distance being regulated by a screw and nut. By pressing 
 with the fingers upon the Microtome it will close, and open 
 when they are removed. The length of the cutting blades is 
 l^inch. 
 
 The ordinary scalpels or knives are usually too large for all 
 purposes ; those, however, which are used in operations on the 
 eye will be of service. 
 
 For making fine sections, a scalpel or a razor may be em- 
 ployed, but for soft substances, as the liver, spleen, and kid- 
 
 ney, a knife with two parallel blades, called Valentin's Knife, 
 Fig. 33, may be used with advantage. Dissecting needles 
 may be straight or curved. One of the latter fixed in a pro- 
 
 Fig. 34. 
 
 per handle, is represented in Fig. 34. These are very service- 
 able instruments for separating or tearing asunder delicate 
 tissues. 
 
120 THE MICROSCOPIST. 
 
 As most dissections are made under water, convenient troughs 
 are necessary. They may be from two inches to a foot long 
 and of a proportionate breadth and depth. Earthenware, or 
 glass, is the best material. One may be prepared with a flat 
 piece of cork cemented to the bottom, inside, by marine glue. 
 
 Loaded corks are flat pieces of cork with sheet lead cemented 
 to their under surface with Burgundy pitch, so that they may 
 readily sink in the water. To these corks the subject to be 
 dissected is fastened with pins. 
 
 For vermiform animals, long, narrow, semicylindrical plates 
 are best ; to the convex surface of which they may be fastened, 
 with the legs (if any, as in Myriopoda) hanging along the sides. 
 
 Rests are inclined planes of wood ; one on each side of the 
 trough holding the specimen. If the Dissecting Microscope, 
 represented by Fig. 5, is used, neither rests nor troughs will 
 be required, other than are furnished with the instrument ; 
 unless it be troughs for specimens not immediately under exa- 
 inination. 
 
 In addition to these instruments, a small syringe, camel's- 
 hair pencil brushes, &c. &c., will be found useful. 
 
 For some objects, which are with difficulty kept in place for 
 dissection, a little plaster may be mixed to the consistence of 
 thin cream, and by means of a brush may be coated over those 
 parts which are desirable to be fixed; then, by placing it in a 
 small box or other suitable mould, the plaster may be poured 
 round it, and allowed to harden. In this case a loaded cork 
 is unnecessary, the weight of the plaster being generally suf- 
 ficient. The plaster may be colored with ink, &c., if its white- 
 ness is fatiguing to the eye. 
 
 Before dissection, a good light should be thrown upon the 
 object by means of the condensing lens (Fig. 15). 
 
 A dissecting microscope is also generally necessary. This 
 may be one specially designed for the purpose, as Fig. 5; or the 
 
DISSECTING OBJECTS. 121 
 
 compound microscope with an erector, page 44 ; or a lens 2 or 
 3 inches focal length, or even smaller, fastened to a stem, so as 
 to be adjustable over the object. 
 
 The following account of Swammerdam's dissections com- 
 mends itself to all microscopists. It is condensed from an 
 extract in Adams's Essays, from Boerhaave's Life of Swam- 
 merdam. 
 
 In the preparation of objects, no man was ever more suc- 
 cessful or more indefatigable than Swammerdam. His chief 
 art seems to have been in constructing very fine scissors, and 
 giving them an extreme sharpness; these he made use of to 
 cut very minute objects, because they dissected them equally, 
 whereas knives and lancets, if ever so fine and sharp, are apt 
 to disorder delicate substances. His knives, lancets, and styles, 
 "were so fine that he could not see to sharpen them without a 
 magnifying glass. 
 
 He was also dexterous in the management of small glass 
 tubes, which were no thicker than a bristle, and drawn to a 
 fine point atone end, but thicker at the other. These he made 
 use of to show and blow up the smallest vessels discoverable 
 by the microscope; to trace, distinguish, and separate their 
 courses and communications, or to inject them with subtile 
 liquors. 
 
 He used to suffocate insects in spirits of wine or turpentine, 
 and likewise preserved them some time in these liquids; by 
 which means he kept the parts from decomposition, and added 
 to them such strength and firmness as rendered the dissections 
 more easy. When he had divided transversely the little 
 creature he intended to examine, and carefully noted every- 
 thing that appeared without further dissection, he then pro- 
 ceeded to extract the viscera in a very cautious and leisurely 
 manner; first taking care to wash away and separate, with 
 
 11 
 
122 THE MICROSCOPIST. 
 
 fine pencils, the fat with which insects are plentifully sup- 
 plied. 
 
 Sometimes he put into water the delicate viscera of the 
 insects he had suffocated; and then shaking them gently, he 
 procured himself an opportunity of examining them, especially 
 the air-vessels and trachese, which by this means he could 
 separate from all the other parts. Again, he has frequently 
 made punctures in other insects with a needle, and after 
 squeezing out all their moisture through the holes made in 
 this manner, he filled them with air, by means of slender glass 
 tubes, then dried them in the shade, and anointed them with 
 oil of spike, by which means they retained their proper forms 
 for a long time. He had a singular secret whereby he could 
 preserve the nerves of insects as limber and perspicuous as ever 
 they had been. Some insects he injected with wax instead of 
 air. 
 
 He discovered that the fat of all insects was perfectly solu- 
 ble in oil of turpentine; thus he was enabled to show the 
 viscera plainly, only after this operation he used to cleanse and 
 wash them well and often in water. He frequently spent 
 whole days in thus cleansing a single caterpillar of its fat, in 
 order to discover the true construction of this insect's heart. 
 
 His singular sagacity in stripping off the skin of caterpillars 
 that were on the point of spinning their cones deserves notice. 
 This he effected by letting them drop by their threads into 
 scalding water, and suddenly withdrawing them ; for by this 
 means the epidermis peeled off very easily ; and when this was 
 done, he put them into distilled vinegar and spirit of wine, 
 mixed together in equal proportions, which, by giving a proper 
 firmness to the parts, afforded an opportunity of separating 
 them, with very little trouble, from the exuviae, or skins, with- 
 out any danger to the parts ; so that by this contrivance the 
 
DISSECTING OBJECTS. 123 
 
 pupa could be shown to be wrapped up in the caterpillar, and 
 the butterfly in the pupa. 
 
 Those who look into the works of Swammerdam, will be 
 abundantly gratified, whether they consider his immense labor 
 and unremitting ardor in these pursuits, or his wonder- 
 ful devotion and piety. On one hand, his genius urged him 
 to examine the miracles of the Great Creator in his natural 
 productions; while, on the other, the love of that same All- 
 perfect Being, rooted in his mind, struggled hard to persuade 
 him that God alone, and not his creatures, was worthy of his 
 researches, love, and attention. 
 
 In addition to the chapter on procuring objects, a few further 
 remarks on the internal anatomy of insects will not be out of 
 place. For the microscopic anatomy of other parts of the ani- 
 mal organization, the reader is referred to Chapter V. 
 
 1. Tracheae, or Respiratory System of Insects. Respiration 
 in insects is effected by means of two great longitudinal ves- 
 sels or canals called tracheae, running along the sides of the 
 body beneath the outer integuments and muscles, terminating 
 in breathing pores (spiracles or stigmata). These pores or 
 spiracles are placed along each side of the body in terrestrial 
 insects, and are furnished with a beautiful mechanism to pre- 
 vent the admission of foreign particles. The tracheae emit an 
 infinite number of ramifications, extending to all parts of the 
 body, so that air circulates freely in every pa'rt. The tracheae 
 consist of an elastic spiral cartilage rolled up into a tube, 
 lined on each side with cellular tissue. In Fig. 35 the tracheae 
 of the larva of the Cossus ligniperda, or willow moth, is re- 
 presented. Along each side of the caterpillar are seen the 
 spiracles. 
 
 To obtain the tracheae, &c., the insect should be placed in a 
 small trough with water, and be securely fixed to a loaded cork. 
 The body being laid open, next to the large viscera, the tra- 
 
124 
 
 THE MICROSCOPIST. 
 
 chese will become visible. These vessels, naturally filled with 
 air, are of a beautiful metallic white color, which produces a 
 very pretty effect upon the darker grounds of the other organs 
 upon which they run. The stomach and intestinal canal, if 
 large and transparent, will exhibit the minute ramifications of 
 
 Fig. 35. 
 
 the tracheae the best ; for this purpose, after being slit open 
 and well washed, they should be either mounted in fluid or be 
 placed on a slide to dry. If care be taken in the mounting, 
 they will show very well in balsam. When the entire tracheal 
 system is required to be dissected from the larva of an insect, 
 all the viscera should be taken out ; the main trunks with their 
 tufts of branches, will then be seen running down on either 
 side of the body, and if care be taken in the dissection, the 
 whole system may be removed from the cavity, and laid out, 
 or rather floated on, a slide to dry, previous to being mounted 
 in balsam. The spiracles require very little dissection. They 
 
DISSECTING OBJECTS. 
 
 125 
 
 may be cut from the body with a scalpel or pair of scissors, and 
 be mounted in fluid or in balsam. 
 
 2. The Digestive System consists of the pharynx; the oeso- 
 phagus, or gullet ; the craw, or crop ; the gizzard, or ventri- 
 culus , the stomach, or duodenum ; the intestines ; and a 
 number of slender membranous tubes, filled with a fluid 
 analogous to bile. In addition to these, the salivary glands 
 may be mentioned.- '. .. 
 
 There is a very great variety in the digestive apparatus of 
 insects. In those which feed on flesh, the alimentary canal is 
 short, as in the higher animals, and in the vegetable eaters it 
 
 Fig. 36. 
 
 is long. There are also differences of structure which clearly 
 show the adaptation of means to ends. A, Fig. 36, is the 
 
 11* 
 
126 THE MICROSCOPIST. 
 
 digestive system of Melolontha. B, is that of Blatta Ameri- 
 cana (American Cockroach), a is the oesophagus, b the crop, at 
 the bottom of which is the gizzard, c, consisting of several 
 teeth arranged like a funnel, with the apices of the teeth in 
 the centre. Another view of the gizzard is seen at C. The 
 bile-tubes or liver are shown at d, and the salivary glands at e. 
 Attached to the stomach, just below the gizzard, are eight 
 blind sacs, /, the use of which is unknown, but is supposed 
 to be analogous to the pancreas. 
 
 The salivary glands, stomach, &c., should be generally 
 mounted in fluid. Gizzards may be put up in balsam. The 
 gizzard of a cricket is an interesting object; it has over two 
 hundred teeth. They may be prepared by making a longitu- 
 dinal incision and spreading out to dry ; or by inflating, after 
 the gizzard has been cleaned of its contents, by means of a 
 small syringe. After drying in the latter mode it may be cut 
 in two, so as to show the parts in their natural position. 
 
 The Nervous System consists of two medullary cords or 
 threads, which run along the middle of the abdomen inside, 
 exhibiting a series of knots or ganglia. 
 
 Fig. 37 exhibits the nervous system of a caterpillar, from a 
 preparation of Dr. Goadby's. The double ganglion, A, seems 
 to occupy the place of the cerebellum, and B, also double, and 
 transverse to the others, answers to the cerebrum. C, C, the 
 two cords uniting them. E, the space through which the 
 oesophagus passes. F, F, F, the ganglia which unite the two 
 cords. The distribution of the nerves through the body is 
 from the ganglia. The apparent exception to this, as at D, 
 are proven, by Dr. Goadby's investigations on the Limulus, to 
 be, in fact, arteries, as they have been injected. Coagulated 
 insect blood is white, hence they appear like nerves. 
 
 4. The Circulatory System is placed along the back, and 
 consists of a heart or dorsal vessel ; which is a tube divided 
 
DISSECTING OBJECTS. 
 
 127 
 
 into chambers, separated from each other by valves. There are 
 also valves at the sides to receive the blood from the venous 
 sinuses of the body. But a single artery has been seen, which 
 goes to the head, dividing into three branches. It was thought 
 that the blood exuded through the vessel and found its way 
 through the body as it best could, back to the heart ; but in 
 dissecting a Limulus (king crab), Dr. Goadby traced the artery 
 into certain large sacs or vessels, evidently answering the pur- 
 pose of veins (venous sinuses). It 1s probable the same holds 
 
 Fig. 37. 
 
 Fig. 38. 
 
 good of insects. Fig. 38 represents the dorsal vessel in the 
 larva of Ephemera. The arrows indicate the current of the 
 fluid. 
 
128 THE MICROSCOPIST. 
 
 In dissecting the heart or dorsal vessel, the body must be 
 opened from the ventral surface, all the viscera removed, and 
 the vessel left with its ligaments attached to the upper rings of 
 the body. Or the superior segments of the body may be re- 
 moved by cutting with scissors along the lateral membranous 
 bands and removing all the upper part of the abdomen. The 
 dorsal vessel may then be slit open. This dissection requires 
 much care and great steadiness of hand. 
 
 5. The muscular system of insects is very extensive. Lyonet 
 dissected and described 4061 in the caterpillar of the goat moth 
 {Cossus ligniperda). M. Straus-Durekheim and others recom- 
 mend that the insect should be cut in two a little to the right 
 or left of the median line, so that the half to be examined shall 
 be a little larger than the other, that the azygos muscles, &c., 
 in the centre be not injured. Beginning then with the internal 
 profile, layer after layer of muscles should be dissected. 
 
 By previous maceration in dilute alcohol the muscles are 
 slightly hardened. If left too long, however, they will become 
 detached from the integument. 
 
CHAPTER IX. 
 
 THE CELL. DOCTRINE OF PHYSIOLOGY. 
 
 REFERENCE has already been made at page 107 to the cause 
 of vitality ; alluding to it as a peculiar property impressed by 
 the Creator on all organized structure, a property altogether 
 distinct from Volition and Sensation, which exclusively belong 
 to animals, and which point out the existence of a special 
 entity, or being, resident in the organism, but whose properties 
 cannot properly be referred either to matter or its organization. 
 
 Respecting the essential nature of the vital principle, much 
 speculation has been uselessly employed. Some have con- 
 founded it with the entity, or being, in the animal, which 
 perceives and wills. But this is manifestly an error, inasmuch 
 as it pertains also to vegetables. Very many parts of the 
 organization, also, have an independent vitality (without special 
 sensibility), separate from that of other parts, as we shall see 
 in the progress of this chapter. It seems, therefore, most rea- 
 sonable to define it as a peculiar property of organization ; as 
 gravitation, electricity, &c., are special properties of matter 
 under other circumstances, the essential nature of which are 
 just as mysterious as that of Life. 
 
 Mysterious as this subject is, it is nevertheless interesting to 
 trace the origin and development of organized structures ; and 
 the progress of modern science has supplied us with the means 
 of instruction. Chemistry teaches us that the ultimate elements 
 
130 THE MICROSCOPIST. 
 
 of organized bodies are identical with the elements of other 
 bodies ; and the microscope detects the earliest forms produced 
 by the vital process, and the part sustained by them in the 
 development of each species. 
 
 Chemical analysis shows, that what are termed simple ele- 
 ments, as oxygen, hydrogen, carbon, nitrogen, sulphur, &c., are 
 peculiarly arranged in all organized bodies; having special 
 affinities which they do not possess in unorganized substances, 
 or bodies destitute of life. These peculiar affinities form a class 
 of compound substances called proximate principles, or organic 
 compounds, or organizable substances. They are obtained by 
 the analysis of organized textures : such are albumen, fibrin, 
 starch, gluten, &c. 
 
 Owing to the feeble affinity of the simple elements in the 
 organic compounds, there is a great tendency in them to enter 
 into new combinations, forming what are called secondary 
 organic compounds. Such are urea, uric acid, pepsine, sugar 
 of milk, &c. 
 
 Hitherto, no one has succeeded in producing the true proxi- 
 mate principles by chemical synthesis, and it is doubtful if they 
 will ever be produced elsewhere than in the living organism. 
 Some of the secondary organic compounds have, however, been 
 formed in the laboratory of the chemist ; as the production of 
 urea from cyanate of ammonia through the action of heat, which 
 has been effected by Wbhler. 
 
 " The simplest and most elementary organic form with which 
 we are acquainted, is that of a cell, containing another within 
 it (nucleus), which again contains a granular body (nudeolus)" 
 See Fig. 39. 
 
 " This appears, from the interesting researches of Schleiden 
 and Schwann, to be the primary form which organic matter 
 takes when it passes from the condition of a proximate 
 
THE CELL-DOCTRINE OP PHYSIOLOGY. 131 
 
 principle to that of an organized structure." (Todd and Bow- 
 man.') 
 
 There are some animal tissues, however, which seem to have 
 a lower grade of organization than cells, being apparently 
 
 Fig. 39. 
 
 produced by the simple solidification of the plastic or organiza- 
 ble fluid : this fluid is, however, prepared by cells, and is set 
 free by their rupture. This seems to be the case with the deli- 
 cate membrane known as the Basement or Primary Membrane, 
 beneath the epidermis or epithelium. According to Dr. Car- 
 penter, in many specimens of this membrane, no vestige of cell- 
 structure can be seen, and it resembles that of which the walls 
 of the cell are themselves constituted. In other cases it pre- 
 sents a granular appearance under the microscope, and is then 
 supposed by Henle to consist of the coalesced nuclei of cells, 
 whose development has been arrested. Other specimens of 
 basement membrane, however, described by Goodsir, present a 
 distinctly cellular structure, the cells being polygonal, and each 
 having its own granular nucleus. 
 
 Cells are formed in two ways ; either in a previously existing, 
 structureless fluid called a blastema, or within the interior of 
 previously existing cells. In the first method, the plastic fluid 
 becomes opalescent from the deposition of a number of nudeoli; 
 several of these become aggregated, and form the nucleus, within 
 which the nucleolus can still be seen. This nucleus is called 
 the cytoblast (from xuroj, a vesicle, and /3Xaso, a germ), or 
 cell-germ. From the side of this nucleus a thin transparent 
 membrane projects, like a watch crystal from the dial, and 
 
132 THE MICROSCOPIST. 
 
 gradually enlarges till at last the nucleus is seen only as a spot 
 on its wall. The whole is then called a nucleated cell, or ger- 
 minal cell. The fluid in which the granules are fir'st deposited 
 is called the cytoblastema. 
 
 In the second method of development, each granule of the 
 nucleus has the power of developing a cell, so that the parent 
 cell becomes filled with one or more generations of new cells, 
 which may either disappear entirely, or by the rupture of the 
 original cells the contents may be scattered, and undergo an 
 independent development. 
 
 Sometimes several nucleoli are seen within one nucleus, and 
 several nuclei within one cell. 
 
 Each cell is an independent organ, living for itself, and by 
 itself, and depending upon nothing but a proper supply of nu- 
 triment, and of the appropriate stimuli for the continuance of 
 its growth and for the performance of its functions, until its 
 term of life is expired. 
 
 The development of cells goes on at every period during the 
 life of the organism. They are found floating in immense 
 numbers in the blood, chyle, and lymph; and even in dis- 
 eased secretions, as pus. In the inflammatory process they 
 are produced in great quantities ; and the malignant growths, 
 such as cancer and fungus hcematodes, which infest the body, 
 are owing to the same agencies. In short, the nucleated cell is 
 the agent of most of the organic processes, both in the plant 
 and animal, from the dawn of their existence to their full 
 maturation and decline. 
 
 The forms of cells are various (see Fig. 24) ; some being sphe- 
 roidal, others cubical, prismatic, polygonal, or cylindrical. 
 They are subject also to various transformations. Sometimes 
 a number of cylindrical cells are laid end to end, and by the 
 absorption of the transverse partitions form a continuous tube ; 
 as ia the sap vessels of plants, muscular and nervous fibre, &c., 
 
THE CELL-DOCTRINE OF PHYSIOLOGY. 133 
 
 At other times the cells are elongated and fusiform, as in 
 woody fibre ; or they may send forth prolongations, assuming 
 a stellate or irregular appearance, as in the pigment cells of 
 the Batrachia, and Fishes, or some of the vesicles in the gray 
 matter of the nervous system. Further, the original bounda- 
 ries of the cells may be altogether lost, from their coalescence 
 with each other ; or their cavities be so occupied by internal 
 deposits that they may be mistaken for solid fibres. 
 
 The nuclei are also subject to change of form. In some 
 instances we find it sending out radiating prolongations, so that 
 it assumes a stellate form, like that of the cells of the Gera- 
 
 Fig. 40. 
 
 nium-petal, Fig. 40 ; this seems also to be the case with the 
 nuclei of the bone cells. In vegetables, the wall of the cell 
 always remains, while in bone it disappears, and ithe canaliculi 
 anastomose. In other cases it seems to resolve itself into a 
 fasciculus of fibres ; and this Henle conceives to be the origin 
 of the yellow fibrous tissue. Further, it may separate into a 
 number of distinct fibres, each composed of a linear aggre- 
 gation of granules; in this manner, the dental tubuli appear 
 
 12 
 
134 THE MICROSCOPIST. 
 
 to be formed. Lastly, Dr. Carpenter thinks it may disperse 
 itself still more completely into its component granules ; by 
 the reunion of which certain peculiar vibrating filaments (the 
 so-called spermatozoa), may be formed. 
 
 " In the lowest and simplest forms of living beings," says 
 Dr. Carpenter, " such as we meet with among the humblest 
 cellular plants, we find a single cell making up the whole 
 fabric. This cell grows from its germ, absorbs and assimilates 
 nutriment, converts a part of this into the substance of its 
 own cell-wall, secretes another portion into its cavity, and pro- 
 duces from a third the reproductive germs that are to continue 
 the race; and having reached its own term of life, and completed 
 the preparation of these germs, it bursts and sets them free 
 every one of these being capable, in its turn, of going through 
 the same set of operations. In the highest forms of vegetable 
 life, we find but a multiplication of similar cells ; amongst which 
 these operations are distributed, as it were, by a division of labor ; 
 so that, by the concurrent labors of all, a more complete and 
 permanent effect may be produced." 
 
 Of the development of animal tissues, Todd and Bowman 
 present the following interesting account, in their " Physiolo- 
 gical Anatomy and Physiology of Man." 
 
 " The prevailing mode in which the development of animals 
 takes place, is by the formation, within the parent, of a body 
 containing the rudiments of the future being, as well as a store 
 of nutrient material sufficient to nourish the embryo for a 
 longer or shorter period. This body is called the ovum or egg. 
 It is of thatfform which, in a former page (see Fig. 39, page 
 131), has been described and delineated as the simplest which 
 organization produces. It consists of a vesicular body filled 
 by a fluid, and enclosing another, within which is a third, con- 
 sisting of one or more minute, but clear and distinct granules. 
 The first or vitelline membrane of the ovum, is the wall of a 
 cell ; it is composed of homogeneous membrane : the second, 
 
THE CELL-DOCTRINE OF PHYSIOLOGY. 135 
 
 or the germinal vesicle of the egg, is the nucleus of the first; 
 and the third, which is called by embryologists the germinal 
 spot, is a nucleolus to the second. It appears from the re- 
 searches of Wagner and Barry, that the nucleus or germinal 
 vesicle precedes the formation of the vitelline membrane, but 
 the precise relation, as to the period of its formation, of the 
 nucleolus or germinal spot to the nucleus, has not yet been 
 satisfactorily made out. The germinal vesicle and spot become 
 the seat of a series of changes, which give rise to the develop- 
 ment of new cells, for the formation of the embryo. 
 
 " At this period the embryo consists of an aggregate of cells, 
 and its further growth takes place by the development of new 
 ones. This may be accomplished in two ways : first, by the 
 development of new cells within the old, through the subdivi- 
 sion of the nucleus into two or more segments, and the forma- 
 tion of a cell around each, which then becomes the nucleus of 
 a new cell, and may in its turn be the parent of other nuclei : 
 and secondly, by the formation of a granular deposit between 
 the cells, in which the development of the new cells take 
 place. The granules cohere to each other in separate groups 
 here and there, to form nuclei, and around each of these a 
 delicate membrane is formed, which is the cell-membrane. 
 
 " In every part of the embryo the formation of nuclei and 
 of cells goes on in one or both of the ways above mentioned ; 
 and by and by, ulterior changes take place, for the production 
 of the elementary parts of the tissues." 
 
 The mode of development just referred to may be illustrated 
 by the following cuts. Fig. 41 exhibits a section of one of 
 the branchial cartilages of the young tadpole. Within the 
 large parent-cells, that are held together by intercellular sub- 
 stance, a, I), Cj we observe secondary cells in various stages of 
 development : at d, the nucleus is single ; at e, it is dividing 
 into two ; in the adjoining cell, the division into two nuclei 
 d f and e', is complete ; at /*, two such nuclei are enclosed within 
 
136 THE MICROSCOPIST. 
 
 a common cell-membrane ; at i, we see three new cells (one of 
 them elongated, and probably about to subdivide) within the 
 parent ; and in each of the two groups at the top and bottom 
 
 Fig. 41. 
 
 of the figure, we have four cells, separated by partitions of in- 
 tercellular substance, but having manifestly originated from 
 one parent cell. 
 
 Fig. 42 represents endogenous cell-growth in cells of a me- 
 liceritous tumor; a, cells presenting nuclei in various stages 
 of development into a new generation; 6, parent-cell, filled with 
 a new generation of young cells, which have originated from the 
 granules of the nucleus. 
 
 The following arrangement of animal tissues is based upon 
 that adopted by Dr. Carpenter. 
 
 1. Simple membrane; homogeneous, or nearly so, employed 
 alone, or in the formation of compound membranes. Its prin- 
 cipal character in extension, but its ultimate structure de- 
 fies the highest powers of the microscope. Examples are seen 
 
THE CELL-DOCTRINE OF PHYSIOLOGY. 137 
 
 in the posterior layer of the cornea, capsule of the lens, sarco- 
 lemma of muscle, &c. 
 
 2. Simple fibrous tissues, including the white and yellow 
 fibrous tissues, and the areolar tissue, which is formed from 
 
 Fig. 42. 
 
 them. Henle believes the white fibrous tissue to be formed by 
 cells ; the yellow, by nuclei. 
 
 3. Simple cells, floating separately and freely in the fluids, 
 as corpuscles of the blood, lymph, and chyle. 
 
 4. Simple cells developed on the free surfaces of the body, 
 as epidermis and epithelium. 
 
 5. Compound membranes ; composed of simple membrane, 
 and a layer of cells, of various forms (epithelium and epidermis) ; 
 or of aretlar tissue and epithelium ; as mucous membrane, skin, 
 secreting glands, serous and synovial membranes. 
 
 12* 
 
138 THE MICROSCOPIST. 
 
 6. Simple isolated cells, forming solid tissues by their 
 aggregation ; as fat cells, the vesicles of gray nervous matter, 
 absorbed cells of the villi, and the cellular parenchyma of the 
 spleen. In these cases the cells are held together by the blood- 
 vessels and areolar tissue, which pass in between them ; in car- 
 tilage, and other tissues allied to it in structure, the cells are 
 united by intercellular substance, either homogeneous, or of a 
 fibrous character. 
 
 7. Sclerous or hard tissues, in which the cells have been 
 more or less consolidated by internal deposit, and more or less 
 completely coalesced with each other; as the hair, nails, &c. 
 These instances may be more properly ranked under the epi- 
 dermic tissues ; the result of consolidated deposit is more cha- 
 racteristically seen in bones and teeth. 
 
 8. Tubular tissues ; formed by the coalescence of the cavi- 
 ties of cells ; as in the capillary blood-vessels, muscular fibre, 
 tubuli of nerves, &c. 
 
 In some of these, as muscle and nerve, a deposit has taken 
 place subsequently to the coalescence of the original cells. 
 
 To these we may add, 9. Compound tissue; formed of 
 areolar tissue and cartilage ; as fibro-cartilage. 
 
CHAPTER X. 
 
 EXAMINATION OP MORBID STRUCTURES, ETC. 
 
 FOR the purpose of making a microscopic analysis of abnor- 
 mal or other fluids, certain chemicals will be required ; as liquor 
 potassae, ammonia, ether, and alcohol, acetic, nitric, hydrochloric 
 and sulphuric acids; together with a few test-tubes and watch- 
 glasses. 
 
 In the case of solids, the various kinds of scalpels, dissecting 
 needles, and Valentin's knife, will be useful. 
 
 If the subject for examination be fluid, as blood, pus, mucus, 
 &c., a very small quantity should be put on a clean slide, and 
 covered with a piece of thin glass. A fishing-tube (page 49) 
 will be of service for this purpose. 
 
 If there be sediment in the fluid, it should be allowed to sub- 
 side, when it can be transferred by the fishing-tube to the 
 slide. A small quantity of any reagent which may be de- 
 sired, may be brought in contact with one of the sides of the 
 thin glass cover, when it will gradually insinuate itself between 
 the glasses, and act slowly on what is contained there. In 
 other cases, the cover may be lifted up, and the reagent 
 added. 
 
 In the case of blood, the fluids that require to be added are 
 generally, ordinary water ; serum ; and sugar or salt, dissolved 
 in water ; but in the case of pus and mucus, which approach 
 each other so nearly in many of their characters, it becomes of 
 importance to have some test whereby they may be distinguished 
 
140 THE MICROSCOPIST. 
 
 from each other. The fluid employed for this purpose is 
 acetic acid. When this is added to a fluid where pus is pre- 
 sent, the globules swell up, and several large, transparent nuclei 
 make their appearance ; but when it is added to a fluid where 
 mucus is present, the globules also enlarge and show their nu- 
 clei, but not so plainly as the pus, and the liquid, termed liquor 
 muci, in which the globules float, is instantly coagulated into a 
 semi-opaque corrugated membrane. 
 
 The presence of fatty matter is ascertained by sulphuric ether, 
 which readily dissolves the oily part, and leaves the membran- 
 ous cell-wall untouched. 
 
 Earthy matters require the aid of the acids for their solu- 
 tion ; these should be added in a dilute form, so that their sol- 
 vent action may be more easily witnessed. 
 
 Solid parts, as tumors, &c., that are to be examined as 
 transparent objects, with high powers, require to be cut into 
 very thin slices, and separated, if necessary, by the needle- 
 points. The sections should be placed on a slide, and a little 
 serum or white of egg in water, added, in order to float out 
 certain of the parts, and to lessen the refraction of the light at 
 the edges of the object. Water will answer the purpose for some 
 of the hard tissues, but where nucleated or other cells, and 
 nervous matter, are present, its use is inadmissible. 
 
 It is necessary to state, that the examination of all morbid 
 structures should be made as soon as convenient after their re- 
 moval from the body, as changes of form in the softer sub- 
 stances speedily take place ; but if some time has elapsed, the 
 part from which the sections are taken should be at some dis- 
 tance from the surface, in order that they may be as little 
 altered as possible by the action of the air. 
 
 The foregoing directions have been condensed from those of 
 Mr. Quekett, to whose book we have already been much in- 
 debted during the progress of this work. 
 
MORBID STRUCTURES, ETC. 141 
 
 It was at one time " fondly hoped" (says Dr. McClellan), 
 " that by the aid of powerful microscopes we could be able to 
 detect the pre-existing germs of all organic diseases in the 
 general circulation, and decide not only as to the species of 
 affection, but also concerning the degree of constitutional con- 
 tamination. It was even thought that cancers could thus be 
 distinguished from scrofula and all other more innocent dis- 
 eases; while, at the same time, we could form a conclusive 
 opinion as to the propriety of attempting or declining a sur- 
 gical operation, or of instituting any mode of local treatment 
 for the purpose of affording relief. But all such attempts have 
 proved to be illusory, and we can gather no other practical 
 knowledge from the use of the microscope than what is con- 
 nected with the minute anatomy of the morbid structures after 
 they have been elaborated." With all deference to the opinion 
 of so truly a great mind as the lamented McClellan, we may be 
 permitted to remark, that notwithstanding much has been done 
 by the labors of .European and other observers, minute patho- 
 logical observation is still in its infancy; yet it has made a 
 deep impression upon the study of medical science. When 
 " the minute anatomy of the morbid structures" shall be fully 
 known, our knowledge of organic diseases will have advanced 
 to a great degree of perfection. Dr. McClellan is not himself 
 insensible of the advantages to be derived from microscopic in- 
 vestigations, although we think he places too little value upon 
 them. He says, " Chemical analyses and microscopic re- 
 searches have lately proved that a great number of cases (of 
 tumors) which were once thought to be scirrhous, or cartila- 
 ginous, or osteo-sarcomatous, are really composed of condensed 
 fibrine of the blood, sometimes partially altered into albumen 
 or gelatin." 
 
 The microscopic appearance of a fibrous tumor is exhibited 
 in Fig. 43 (after Yogel). It shows interlacing fibres, C. Pri- 
 
142 THE MICROSCOPIST. 
 
 mary cells with nuclei and nucleoli, A, and the same cells 
 elongated and becoming caudate, B. The interlacing fibres 
 appear to be identical with the fibres of coagulated lymph. 
 
 Fig. 43. 
 
 C 
 
 Malignant growths may be divided into three classes of 
 disease. 1. Scrofula, and its varieties. 2. Carcinoma, or 
 scirrho-cancer. 3. Encephaloid disease, or medullary fungus. 
 
 1. Scrofulous growths present three forms of manifestation. 
 In the lymphatic ganglia and in the conglomerate glands ; in 
 well-defined spherical tubercles, which appear first as small 
 points or grayish granules ; and depositions which appear 
 during the progress of typhus fever, between the muscular and 
 mucous coats of the intestines, in the mesenteric glands, in and 
 under the mucous membrane of the trachea, and sometimes in 
 the substance of the lungs and spleen. Fig. 44 shows the 
 microscopic appearance of typhous matter from the mesenteric 
 glands. A, an amorphous, slightly granular mass, of a 
 brownish-white color, with an immense number of cells depo- 
 sited ; B ; the amorphous mass treated with acetic acid, by which 
 
MORBID STRUCTURES, ETC. 143 
 
 it was rendered transparent, and gradually dissolved, upon which 
 many minute cells with a sharp outline came into view, being 
 unaffected by the acid (Yogel). 
 
 Fig. 44, 
 
 There seems no distinction between tuberculous matter and 
 that of scrofula or typhus. Fig. 45 exhibits tubercles in vari- 
 ous stages of development. A, B, C, tubercles from the lungs 
 of a young man who died of tuberculosis pulmonum. 
 
 A, B, nuclei in an amorphous cytoblastemaj most of the 
 nuclei contain nucleoli. At C the cytoblastema has disap- 
 peared and the cells are in contact. D, tubercular cells, from 
 the lungs of another young man. Here the cytoblastema has 
 also disappeared, and the nuclei are enclosed in a cell-wall ; 
 no nucleoli are present. 
 
 2. Carcinoma. In cases of true scirrhus, the matrix or 
 stroma is constituted either by a new development of cellular 
 
144 
 
 THE MICROSCOPIST. 
 
 texture, or by an induration and enlargement of the original 
 areolar tissue of the part. The larger and coarser fibres and 
 
 Fig. 45. 
 
 lamellae of this tissue become converted into dense and firm 
 ligamentous bands, which intersect each other in various 
 directions. 
 
 Vogel, and some other writers, describe a second kind of 
 fibres, which occur in a reticulated form, cross-barred, or in 
 irregular meshes. They are distinguished from the first-men- 
 tioned whitish or ligamentous bands, by being insoluble in 
 acetic acid. Fig. 46 (from Yogel, after Miiller), shows the 
 
 Fig. 46. 
 
 fibrous stroma of scirrhus, as seen in the microscope. The 
 meshes are formed by bundles of carcinoma reticulare of the 
 breast, as they appear after the globules have been removed. 
 
MORBID STRUCTURES, ETC. 145 
 
 The dense, firm, bluish-white, or yellowish and amorphous- 
 looking substance which fills the interstices of the stroma is 
 rendered transparent by acetic acid, and by ammonia and other 
 caustic alkalies. This, though deposited in a fluid state, ac- 
 quires its solidity by coagulation, after which it is thought 
 that the peculiar cancer cells, or fibres, which constitute the 
 malignant character of the disease, are developed. 
 
 The principal forms of cells which enter into the composi- 
 tion of cancerous growths are 1. The irregularly caudate or 
 ramifying cells; 2. Larger cells filled with nuclei; and 3. 
 Granular cells filled and covered with granules. Besides these, 
 Vogel describes cells with a thick wall, exhibiting a double 
 contour; double cells formed by the division of one or the 
 fusion of two cells; and pigment cells, enclosing dark, granular 
 pigment. 
 
 The above are transitory or effete cells. The persistent or 
 fibre cells are fusiform, such as occur in the development of 
 areolar tissue, and of simple muscular fibre. They occur in 
 the firm, rarely in the soft forms of cancer, and seem destined 
 for the formation of the areolar tissue, and the intersecting 
 ligamentous bands. In addition to all these, there appear 
 numerous particles or granules of broken-down lymph and fat ; 
 large fat granules and globules ; and a viscid, gelatinous fluid. 
 These latter, however, may be considered adventitious and not 
 essential formations. 
 
 The microscopic appearance of scirrhus (220 diameters) is 
 exhibited in Fig. 47. Small masses that had been pared from 
 a recent section of the tumor, and moistened in water, con- 
 sisted entirely of an accumulation of cells. These were very 
 pale, varying in size and form, being sometimes roundish, a, 
 sometimes oval, 6, or caudate, f, or again of irregular form. 
 The greater number exhibited nuclei, a, 6, and in some a nu- 
 cleolus was visible in the nucleus, c, h; few were devoid of 
 
 13 
 
146 
 
 THE MICROSCOPIST. 
 
 nuclei ; on some, fat globules were observed, </. Between 
 these cells were perceived nuclei with or without nucleoli, d. 
 (Vogel.) 
 
 Fig. 47. 
 
 3. Encephaloid disease or fungoid tumor, differs from scir- 
 rhous cancer chiefly in the great predominance of its transitory 
 or morbidly developed cells over the fibrous and other elemen- 
 tary textures which constitute the stroma (matrix) of the 
 tumor. In carcinomas, the fibrous tissue predominates and 
 gives solidity and firmness to the whole mass. The morbid or 
 cancer cells never tend to develope organized fabrics, but 
 always to disintegration and softening down of the tumor. 
 Their great predominance in encephaloid, therefore, gives the 
 character of brain-like softness and yielding, which is the dis- 
 tinguishing characteristic of this form of "malignant growth. 
 
 Fig. 48 represents encephaloid, from the liver, under the 
 microscope. It appeared wholly composed of cells, which 
 showed distinct nuclei and nucleoli. The cells were mostly 
 roundish or oval, but some were caudate. Acetic acid ren- 
 dered them full and brought the nuclei plainly in view, a. 
 Here and there some nuclei were seen in an amorphous cyto- 
 blastema. 
 
 Although the cells of encephaloid belong to the class of 
 
MORBID STRUCTURES, ETC. 
 
 147 
 
 effete or transitory cells which also occur in cancer, yet there 
 is a difference in the proportions of various kinds of these cells 
 
 Fig. 48. 
 
 in the two classes of tumors. The predominating cells of this 
 kind in fungoid tumor are the very large parent cells, with 
 numerous young cells or cytoblasts in their interior. They are 
 often as large as ^th of- a line in diameter; and the caudate 
 cells are always irregularly caudate or ramifying. 
 
 There are seldom any of the regular caudate or elongated 
 cells of small size, such as go to the formation of the cellular 
 and fibrous tissue, and of true cancers. The fat cells and 
 
 Fig. 49. 
 
 granules are perhaps more abundant than in scirrhus. Fig. 
 49 is the microscopic appearance of encephaloid, consisting of 
 
148 THE MICROSCOPIST. 
 
 cells of different size and form ; round, oval, and caudate, but 
 no one form predominating over the rest. Some are very large, 
 a, enclosing several minute cells with nuclei. Isolated cells, 
 although in a proportionately small number, contained dark 
 granules, b. For further observations on microscopic patho- 
 logy, the reader is referred to VogeFs Pathological Anatomy, 
 and other similar works. 
 
 The Monthly Journal of Medical Science for May, 1847, 
 contained an account of a new instrument for the diagnosis of 
 tumors. It was presented to the Medical Society of Stras- 
 bourg, by M. Kiin, Professor of Physiology in that city. 
 
 " It consists in an exploring needle, having at its extremity 
 a small depression with cutting edges. On plunging this in- 
 strument into a tumor to any depth, we can extract a minute 
 portion of the tissue of which its various layers are composed. 
 In this manner a microscopic examination of the tumor can 
 be practised on the living subject, and its nature ascertained 
 before having recourse to an operation." 
 
 With respect to the Morphology of various pathological 
 fluids, a great deal has been effected by microscopic investiga- 
 tion. In the Microscopic Journal, vol. ii., is a series of essays 
 on this subject, by Dr. David Gruby, translated from the 
 Latin by S. J. Goodfellow, M.D., which are worthy of careful 
 perusal and experimental verification. The results of Dr. 
 Gruby's researches are appended. 
 
MORBID STRUCTURES, ETC. 
 
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 MORBID STRUCTURES, 
 
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CHAPTER XL 
 
 ON MINUTE INJECTIONS. 
 
 MERE dissection, with the most artful management of the 
 scalpel, cannot make a full exhibition of the true structure 
 of animal bodies. The arteries are found, after death, to be 
 emptied of. their contents, and the blood is coagulated in the 
 veins, which appear much collapsed; hence anatomists, in 
 order to examine the circulatory apparatus, are under the 
 necessity of filling these vessels by means of injection, in 
 order to distend them as much as possible, that their ramifica- 
 tions may be clearly seen. More especially is this necessary 
 when it is desired to make an exhibition of the minute 
 capillaries, which are so variously arranged in the different 
 textures and organs of the body. These small vessels, too, 
 require the aid of the microscope to show their size, form, and 
 arrangement. 
 
 The ordinary coarse injection may be made by melting to- 
 gether 16 ounces of bees' -wax, 8 ounces of resin, and 6 fluid- 
 ounces of turpentine varnish, adding such coloring matter as 
 may be desirable, as 3 ounces vermilion, 2 ounces King's 
 yellow, 10 ounces blue verditer, or 5 ounces flake-white. 
 
 This, injected into the blood-vessels by a proper syringe, 
 having its pipe fastened in one of the largest of those vessels, 
 is abundantly sufficient to show the course of the principal 
 arteries and veins. The parts so injected may then be dis- 
 
ON MINUTE INJECTIONS. 159 
 
 sected for this purpose, dried, and varnished, and form excellent 
 illustrations of anatomical lectures. 
 
 When, however, it is desired to demonstrate the capillaries, 
 a finer injection and more delicate manipulation are required. 
 Indeed, it is so difficult an art, and success is so dependent on 
 the combination of various circumstances, that the most ex- 
 perienced are often defeated in their efforts. Yet some of the 
 finest injections I have ever seen were made by those who 
 attempted it for the first time. 
 
 For minute injection (as it is called), the most essential in- 
 strument is a proper syringe. This should be made of brass, of 
 such a size that the tip of the thumb may press on the head or 
 handle of the piston-rod when drawn out, while the body is 
 supported by two of the fingers of the same hand. 
 
 Fig. 50 represents a syringe, with which I have succeeded 
 in making some excellent preparations. A is the cylindrical 
 brass body, on the top of which screws the cap, B, a leather 
 washer being interposed to render it more air-tight. C is the 
 piston, which is of brass, covered with wash-leather. The 
 bottom of the syringe, D, also unscrews, for convenience of 
 cleaning. E is a stop-cock, on the end of which another stop- 
 cock, F, fits closely. On the end of this, one of the injection- 
 pipes, G-, which are of different sizes, may be placed. The 
 transverse wires, across the injection-pipes, are designed for the 
 better security of the pipe in the vessel into which it is fixed ; 
 the thread being tied behind them so that it cannot slip for- 
 wards. A half-dozen pipes, at least, are necessary to accom- 
 pany each instrument. 
 
 In addition to the syringe, a large tin vessel to contain hot 
 water, with two or three lesser ones fixed in it for the injec- 
 tions, will be found useful. 
 
 For very minute injections, as in the Mollusca, &c, a caout- 
 chouc bottle, with a capillary steel tube mounted in wood, 
 
160 
 
 THE MICROSCOPIST. 
 
 ivory, or iron, is recommended by Talk & Henfrey, after Straus 
 Durekheim. The air should be pressed out of the bottle, and 
 
 Fig. 50. 
 
 the pipe placed in the liquid, which will rush in to fill the 
 vacuum, and it is ready for use. They also recommend a tube, 
 or pipette, with flexible stems, so constructed as to receive jets 
 
ON MINUTE INJECTIONS. 161 
 
 of various sizes. This is used by placing the end of the pipette 
 in the mouth, and exhausting the air on forcing the fluid in the 
 vessels. 
 
 To prepare the material for injecting: Take of the finest 
 and most transparent glue, one pound; break it into small 
 pieces, put it into an earthen pot, and pour on it three pints of 
 cold water; let it stand twenty-four hours, stirring it now and 
 then with a stick ; then set it over a slow fire for half an hour, 
 or until all the pieces are perfectly dissolved J skim off the froth 
 from the surface, and strain through a flannel for 'use. Isin- 
 glass, and cuttings of parchment make an excellent size, and 
 are preferable for very particular injections. 
 
 The size thus prepared may be colored with any of the fol- 
 lowing: 
 
 Red. To 1 pint of size, 2 ounces of Chinese vermilion. 
 
 Yellow. Size, 1 pint, -chrome yellow, 2J ounces. 
 
 White. Size, 1 pint, flake-white, 3J ounces. 
 
 Blue. Size, 1 pint, fine blue smalts, 6 ounces. 
 
 It is necessary to remember that whatever coloring matter is 
 employed, must be very finely levigated before it is mixed with 
 the injection. This is a matter of great importance, for a 
 small lump or mass of color, dirt, &c., will clog the minute 
 vessels, so that 'the injection will not pass into them, and the 
 object will be defeated. 
 
 The mixture of size and color should be frequently stirred, 
 or the coloring matter will sink to the bottom. 
 
 Respecting the choice of a proper subject for injecting, it 
 may be remarked, that the injection will usually go farthest in 
 young subjects; and the more the creature's fluids have been 
 exhausted in life, the greater will be the success of the injec- 
 tion. 
 
 Owing to the contraction of the vessels, it is necessary to 
 wait from one to three days after death before attempting the 
 
 14* 
 
162 THE MICROSCOPIST. 
 
 injection. Yet it should not Tbe deferred so long that the ves- 
 sels may become softened, or the injecting material will be ex- 
 travasated. 
 
 To prepare the subject, the principal points to be aimed at 
 are to dissolve the fluids, empty the vessels of them, relax the 
 solids, and prevent the injection from coagulating too soon. 
 For this purpose it is necessary to place the animal, or part to 
 be injected, in warm water, as hot as the operator's hand will 
 bear. This should be kept at nearly the same temperature for 
 some time 'by occasionally adding hot water. The length of 
 time required is in proportion to the size of the part, and the 
 amount of its rigidity. Ruysch (from whom the art of injecting 
 has been called the Ruyschian art) recommends a previous 
 maceration for a day or two in cold water. 
 
 When the size and the subject have both been properly pre- 
 pared, have the injection as hot as the finger can well bear. 
 One of the pipes, G-, Fig. 50, must then be placed in the 
 largest artery of the part, and securely tied. Put the stop- 
 cock, F, into the open end of the pipe, and it is then ready to 
 receive the injection from successive applications of the syringe, 
 A. The injection should be thrown in by a very steady and 
 gentle pressure on the end of the piston-rod. The resistance 
 of the vessels, when nearly full, is often considerable, but it 
 must not be overcome by violent pressure with the syringe. 
 
 If the resistance suddenly ceases or diminishes, it indicates 
 that some vessel is ruptured, and the process must be stopped. 
 If it happens at the commencement of the operation, and the 
 vessel cannot be tied, the injection has failed. 
 
 When as much injection is passed as may be thought advisa- 
 ble, the preparation may be left (with the stop-cock closed in 
 the pipe) for twenty-four hours, when more material may be 
 thrown in. 
 
 The first part of the injecting material forming about a third 
 
ON MINUTE INJECTIONS. 163 
 
 or fourth part of the whole, should be very fluid, so as to be 
 capable of penetrating the smallest vessels ; afterwards the 
 thicker or coarser portion should be thrown in so as to push the 
 first before it. 
 
 As the method of injecting the 'minute capillaries with 
 colored size is often attended with doubtful success, various 
 other plans have been proposed. Ruysch's method, according 
 to Rigerius, was to employ melted tallow, colored with vermi- 
 lion, to which, in the summer, a little white wax was added. 
 
 Mr. Rauby's material, as published by Dr. Hales, was resin 
 and tallow, of each two ounces, melted and strained through 
 linen ; to which was added three ounces of vermilion, or finely 
 ground indigo, which was first well rubbed with eight ounces of 
 turpentine varnish. 
 
 Dr. Monro recommended colored oil of turpentine for the 
 small vessels, after the use of which he threw in the common 
 coarse injection. 
 
 Professor Breschet frequently employed with success milk, 
 isinglass, the alcoholic solution of gum-lac, spirit varnish, and 
 spirit of turpentine; but he highly commends the coloring 
 matter extracted from campeachy, fernambouc, or sandal woods. 
 He says, "The coloring matter of campeachy wood easily dis- 
 solves in water and in alcohol; it is so penetrating that it be- 
 comes rapidly spread through the vascular networks. The sole 
 inconvenience of this kind of injection is, that it cannot be 
 made to distend any except most delicate vessels, and that its 
 ready penetration does not admit of distinguishing between 
 arteries, veins, and lymphatics." He also recommends a solu- 
 tion of caoutchouc. 
 
 Another process, which may be termed the chemical process, 
 was published in the Comptes Rendus, 1841, as the invention of 
 M. Doyere. though the credit of first suggesting it is due to Dr. 
 Goddard, of Philadelphia. According to this, an aqueous solu- 
 tion of bichromate of potass is propelled into the vessels; and 
 
164 THE MICROSCOPIST. 
 
 after a short time, in the same manner and into the same ves- 
 sels an aqueous solution of acetate of lead is injected. This is 
 an excellent method, as the material is quite fluid, and the 
 precipitation of the chromate of lead, which takes place in 
 the vessels themselves, gives a fine sulphur-yellow color. 
 
 A red precipitate is obtained by iodide of potassium and bi- 
 chloride of mercury ; blue, by the ferrocyanide of potassium 
 and peroxide of iron ; &c. 
 
 Dr. Goadby has improved upon the process last named by 
 uniting to the chemical solutions a portion of gelatine. The 
 following is his formula, originally published in the London 
 Lancet, and again in the Medical Examiner, March, 1850. 
 
 Saturated solution of bichromate of potash, 8 fluid ounces; 
 water, 8 ounces ; gelatine, 2 ounces. 
 
 Saturated solution of acetate of lead, 8 fluid ounces; water, 
 8 ounces; gelatine, 2 ounces. 
 
 Dr. Gr. gives the following remarks respecting this process : 
 "The majority of preparations, thus injected, require to be 
 dried, and mounted in Canada balsam. Each preparation, 
 when placed on a slip of glass, will necessarily possess more 
 or less of the colored infiltrated gelatine (by which, he 
 alludes to the gelatine, colored by the blood, which, together 
 with the acetate of potash resulting from the chemical decom- 
 position, may have transuded through the coats of the vessel), 
 which, when dry, forms, together with the different shades of 
 the chromate of lead, beautiful objects, possessing depth and 
 richness of color. The gelatine also separates and defines 
 the different layers of vessels. By this injection the arteries 
 are always readily distinguishable by the purity and brightness 
 of the chromate of lead within them, while the veins are de- 
 tected by the altered color imparted by the blood. 
 
 " Those preparations which require to be kept wet, can be 
 
ON MINUTE INJECTIONS. 165 
 
 preserved perfectly in my B fluid specific gravity 1-100; 
 the A fluid destroys them. 
 
 " I would recommend, that the slips of glass employed for 
 the dry preparation be instantly inscribed with the name of 
 the preparation, written with a diamond, for, when dry, it is 
 very difficult to recognise one preparation from another, until 
 the operator's eye be educated to the effects of this chemico- 
 gelatinous injection. Where so much wet abounds gummed 
 paper is apt to come off. 
 
 " When dry, it is sufficient for the purpose of brief exami- 
 nation by the microscope, to wet the surface of a preparation 
 with clean oil of turpentine; immediately after examination, 
 it should be put away carefully in a box, to keep it from the 
 dust, until it can be mounted in Canada balsam. 
 
 " Although highly desirable, as the demonstrator of the 
 capillaries of normal tissues, I do not think this kind of injec- 
 tion fitted for morbid preparations, the infiltrated gelatine 
 producing appearances of a puzzling kind, and calculated to 
 mislead the pathologist. 
 
 "In preparing portions of dried, well-injected skin, for exa- 
 mination by the microscope, I have tried the effect of dilute 
 nitric acid, as a corroder, with very good results. But, proba- 
 bly, liquor potassae would have answered this purpose better. 
 
 "When size injection is to be employed, colored either with 
 vermilion or the chromate of lead, the animal should be pre- 
 viously prepared by bleeding, to empty the vessels: for if 
 they be filled with coagulated blood, it is quite impossible to 
 transmit even size, to say nothing of the coloring matter. 
 Hence the difficulty of procuring good injections of the human 
 subject. 
 
 "But with the 'chemico-gelatinous' injections no such pre- 
 paration is necessary, and success should always be certain, for 
 the potash liquefies the blood, while constant and long-con- 
 
166 THE MICROSCOPIST. 
 
 tinned pressure by the syringe drives it through the parietes of 
 the vessel into the cellular tissue. The large quantity of in- 
 filtrated blood the invariable concomitant of my process 
 characterizes this from all other modes of injecting, and is a 
 distinctive feature of these preparations/' 
 
 Still another, and in some respects a more certain and con- 
 venient plan, has been employed by Dr. Goddard of Philadel- 
 phia. It consists in adding a quantity of sulphuric ether to 
 the finely levigated coloring matter, which is also first ground 
 or mixed with linseed oil, in the manner employed by painters. 
 Upon this plan (as well as upon the last named) I have suc- 
 ceeded in making some beautiful injections of the smallest 
 capillaries, yet I have sometimes failed, owing to the too rapid 
 evaporation of the ether, and the clogging up of the vessels 
 from the early deposition of the solid coloring matter. I have 
 also observed that after the ether has evaporated from the 
 vessels, the particles of coloring material cohere with too little 
 tenacity, so that on putting a section of injected tissue into" 
 turpentine, &c., the color has been washed out from the cut 
 ends of the larger vessels. Perhaps a solution of gum nias- 
 tich, &c., in ether, colored with fine vermilion, &c., will answer 
 the indications better. 
 
 Whatever mode of injection be adopted, it is important that 
 the operator be supplied with sufficient material. The quantity 
 which can be used will surprise any one unaccustomed to the 
 process. 
 
 A foetus maybe injected by the umbilical vein; a uterus, 
 by the hypogastric arteries; the head, by the carotids; the 
 liver, mucous membrane of the intestines, &c., by the portal 
 vein ; an extremity, by the principal artery ; &c. 
 
 The liver, kidney, &c., may be well injected out of the body ; 
 and it is often desirable to use various colors for the different 
 sets of vessels. It will require some practice, however, to judge 
 
ON MINUTE INJECTIONS. 167 
 
 how much pressure is necessary to fill but a single set of vessels. 
 After injection, a considerable time must be allowed for dry- 
 ing. Thin slices may then be cut off, and mounted either in 
 balsam or fluid. 
 
 The villi of the intestines are beautifully exhibited after in- 
 jection. They should be macerated a little while in water, or 
 washed with a syringe, to remove the epithelium and mucus. 
 Animals that feed chiefly on vegetables have longer villi than 
 others. 
 
 The lungs may be injected by the pulmonary artery or vein- 
 In a foetus, however, all the organs may be injected from the 
 umbilical vein. The author's injections and specimens of in- 
 jected lungs confirm the view of Mr. Rainey, that the essen- 
 tial and only true organs of the aeration of the blood are the 
 pulmonary capillaries. 
 
 Injections of the skin may be made by the vein of an ex- 
 tremity. They may then be mounted in fluid, or after drying, 
 sections may be made and put up in balsam. 
 
 The vessels of the choroid membrane and ciliary processes of 
 the eye are often injected in a foetus ; or in the case of an animal, 
 as a cat, rabbit, &c., injected from the heart. The preparation 
 should be kept in fluid. 
 
 Many parts, after injection, require to be macerated in water, 
 or corroded by dilute muriatic acid, &c., in order to exhibit the 
 ramifications of the small vessels. They should be very care- 
 fully handled, or moved, in the macerating liquor, as the slight- 
 est force may break the vessels. When corroded, the pulpy 
 flesh is to be carefully washed away by placing it under a 
 stream of water, flowing very slowly ; or by the use of a syringe 
 with water. 
 
 The lymphatics are usually injected with quicksilver, but 
 M. Rusconi and Professor Breschet, have abandoned this me- 
 thod for the colored material, on account of the mercury fre- 
 
168 THE MICROSCOPIST. 
 
 quently rupturing by its weight the thin, lymphatic vessels 
 and reservoirs. The first-named gentleman, in his researches 
 on the lymphatics of reptiles, employs in place of the usual 
 injecting tube of Walter (used with the mercury), a small 
 silver syringe, together with a kind of trocar, of which the 
 canula is formed from the quill of the wing-feather of the quail 
 or partridge, the trocar being a tolerably large-sized needle, 
 the point of which has three facets. When desirous of in- 
 jecting the lymphatic system of a lizard, tortoise, &c., he re- 
 marks : " I seize with a small pair of forceps the mesentery, 
 close to the vertebral column, where the reservoir of the chyle 
 is situated, and I introduce into it the point of the trocar ; I 
 then retain the quill and withdraw the needle from the tube. 
 This done, I seize with the small forceps the quill, and intro- 
 duce into it the small extremity of the syringe, and push the 
 piston with a force always decreasing." He recommends 
 colored wax, mixed with nut-oil, for the injection. 
 
CHAPTER XII. 
 
 EXAMINATION OF URINARY DEPOSITS. 
 
 THE chemical composition of the urine and urinary deposits 
 has within a few years past attracted much attention, and has 
 contributed much to our knowledge respecting the nature of 
 diseases and their diagnosis. To examine these, the microscope 
 is often an essential instrument. 
 
 Deposits of uric acid and its combinations (called red, or 
 yellow-sand sediments), occur in fever ; acute inflammation ; 
 in rheumatism; in phthisis; in all the grades of dyspepsia; 
 in all or most stages of diseases attended with arrest of per- 
 spiration ; in diseases of the genital apparatus ; from blows and 
 strains of the loins ; from excessive indulgence in animal food ; 
 or from too little exercise. 
 
 The deposition of earthy phosphates (white deposit), should 
 be regarded as of serious importance, always indicating the 
 existence of important functional, and frequently of organic 
 disorder. According to Dr. Bird, they always exist simul- 
 taneously with a depressed state of nervous energy, often 
 general, rarely more local, in its seat. 
 
 Deposits of oxalate of lime are regarded by Dr. G-. Bird as 
 by no means so rare as is generally supposed. He believes 
 that ife owes its origin to sugar, and is caused by derangement 
 of the digestive organs. 
 
 The urine may contain all or any of the elements of the 
 
 15 
 
170 THE MICROSCOPIST. 
 
 blood. The serum may be effused alone, or be accompanied 
 with the red globules. 
 
 Whenever the elements of blood appear in the urine, there 
 is ample proof of the existence of active or passive hemorrhage 
 of the kidneys, or urinary tract. 
 
 Albuminous urine occurs in Bright' s disease, dropsy after 
 scarlatina, &c. 
 
 Pus is met with in the urine as the result of suppuration of 
 the kidney, or of some part of the genito-urinary mucous mem- 
 brane, or of abscesses of the neighboring viscera, opening 
 into the urinary passage. 
 
 The presence of sugar is not uncommon in dyspepsia, and 
 when excessive is diagnostic of diabetes mellitus. 
 
 Kiestein is a whitish, greasy, opalescent pellicle, sometimes 
 found on the urine of pregnant women. 
 
 To examine urinary deposits with the microscope, allow the 
 urine to stand; decant the supernatant fluid; pour the remain- 
 der into a watch-glass ; draw off the small quantity of fluid 
 remaining after a short repose, by means of a pipette ; and then 
 place it on the stage of the microscope. When, however, it is 
 necessary to use high powers, a drop of the sediment should be 
 placed on a glass slide and covered with thin glass. 
 
 If it is desired to mount the object for future examination, 
 it can be covered, when dry, with a drop of Canada balsam, 
 and surmounted with the thin glass. Very transparent objects 
 should be kept in fluid, as weak spirit, water saturated with 
 creasote, or G-oadby's fluid. 
 
 HEALTHY URINE holds in solution a variety of substances, 
 both organic and inorganic. Chemists have not yet succeeded in 
 insulating all its ingredients for examination, but the most 
 important of its solid materials are urea, uric acid, hippuric 
 acid, vesical mucus and epithelial debris, animal extractive, 
 ammoniacal salts, fixed alkaline salts, and earthy salts. 
 
 
EXAMINATION OF URINARY DEPOSITS. 171 
 
 The amount passed by an individual during each twenty-four 
 hours, varies from twenty to fifty ounces, holding in solution 
 from six hundred to seven hundred grains of solid matter. 
 When kept for some time it gradually becomes turbid, and de- 
 posits a sediment of earthly phosphates, previously held in 
 solution by the slight excess of acid present. If kept still 
 longer, it gradually putrefies, and, becoming concentrated by 
 evaporation, deposits small crystals of chloride of sodium, 
 phosphates, and other salts, and eventually becomes covered 
 with a grayish-colored mould. 
 
 Urea appears to be the vehicle by which nearly the whole of 
 the nitrogen of the exhausted tissues of the body is removed 
 from the system. The proportion of urea in healthy urine 
 averages fourteen or fifteen parts in the one thousand. Pure 
 urea may be obtained by first converting it into the oxalate, 
 which is done by adding a strong solution of oxalic acid in hot 
 water, to urine previously concentrated to about one-eighth its 
 bulk, and filtered to free it from the insoluble sediments of 
 phosphates and urates. The crystal of oxalate of urea thus 
 obtained, a, Fig. 51, should be dissolved in hot water, and the 
 solution treated with pulverized chalk as long as effervescence 
 is produced. The urea remains in solution, and may be puri- 
 fied by boiling with animal charcoal, after which it may be 
 crystallized, in four- sided prisms, by careful evaporation. 
 
 Nitrate of urea may be obtained in crystals, b, Fig. 51, by 
 concentrating urine to about one-half its bulk, and adding an 
 equal quantity of nitric acid. If urea be suspected in excess, 
 a drop of the urine, without concentration, may be treated with 
 nitric acid under the microscope. 
 
 The proportion of uric acid in the healthy secretion varies 
 from 0-3 to 1-0 in 1000 parts. Its forms will be represented 
 when we treat of the examination of urinary deposits. It may 
 be obtained from urine concentrated to half its bulk, by adding 
 
172 
 
 THE MICROSCOPIST. 
 
 a few drops of hydrochloric acid ; and allowing it to stand 
 few hours in a cool place. 
 
 Fig. 51. 
 
 Hippuric Acid is generally present in a small quantity in 
 healthy urine, and in certain forms of disease, especially where 
 a vegetable diet has been adopted. Fig. 52 represents some 
 
 Fig. 52. 
 
 of its forms ; a are deposited from an alcoholic solution, and 
 b from a hot aqueous solution. 
 
 When an excess is suspected in urine, it should be evapo- 
 rated to the consistence of syrup and mixed with half its bulk 
 of strong hydrochloric acid. After a few hours the crystals 
 
EXAMINATION OF URINARY DEPOSITS. 173 
 
 may be examined with the microscope, when the tufts will 
 probably be seen, colored pink by the admixture of purpu- 
 rine. If it be present only in small quantity, a few detached 
 needle-like or branched crystals may be seen. It is readily 
 soluble in alcohol and hot water, but not in cold water. 
 
 Vesical Mucus and Epithelial Scales, which may be present, 
 are derived from the internal surface of the bladder and uri- 
 nary passages. The quantity is so small in healthy urine as to 
 be scarcely visible, until, after standing, it has subsided to the 
 bottom of the liquid in the form of a thin cloud. 
 
 Extractive Matter, includes all the uncrystallizable organic 
 matter found in the residue of evaporated urine, which is 
 soluble in water or alcohol. When in excess, the urine ap- 
 pears more highly colored than usual, a large proportion of 
 what is termed extractive, consisting of coloring matter, as 
 purpurine, &c. 
 
 Ammoniacal Salts appear to consist chiefly of the muriate 
 and the urate, the latter salt being the form in which the uric 
 acid present in the urine appears to be held in solution. 
 
 The proportion of ammonia in healthy urine is quite small, 
 but in some diseases, especially in certain kinds of fever, it 
 increases considerably. 
 
 Fixed Alkaline Salts may be obtained by incinerating the 
 evaporated residue of urine, when a white ash will be left, 
 consisting of a mixture of alkaline and earthy salts; the for- 
 mer may be separated from the latter by dissolving in water, 
 in which the earthy salts are insoluble. 
 
 The alkaline salts, which in the healthy secretion usually 
 amount to thirteen or fourteen parts in one thousand, consist 
 of the sulphates of potash and soda, chloride of sodium, chlo- 
 ride of potassium, and phosphate of soda. The crystallized 
 residue, after slowly evaporating a few drops on a piece of glass, 
 usually has the appearance represented in Fig. 53. The cross- 
 
 15* 
 
174 THE MICROSCOPIST. 
 
 lets consist of chloride of sodium ; the more plumose crystals 
 are probably phosphate of soda. 
 
 Fig. 53. 
 
 The Earthy Salts which form the insoluble portion of the 
 ash, and which usually amount in healthy urine to about 1 
 part in 1000, consist of the phosphates of lime and magnesia, 
 together with a small trace of silica. These appear to be re- 
 tained in solution in the urine by the small exoess of acid 
 (probably phosphoric) usually present, and may be precipitated 
 from it by supersaturating with ammonia. The precipitate 
 thus formed consists of a mixture of phosphate of lime, and 
 the double phosphate of ammonia and magnesia, which is 
 also called triple phosphate. These, with the abnormal ingre- 
 dients found in morbid urine, &c., will be treated of when we 
 come to the examination of urinary deposits. It must be 
 borne in mind, however, that a spontaneous precipitate of 
 earthy phosphates is not of itself a proof that they are present 
 in excess, for when the urine is acid, as in health, a considera- 
 ble quantity may be retained in solution, while if it be neutral 
 or alkaline, a comparatively small proportion may be precipi- 
 tated. 
 
EXAMINATION OF URINARY DEPOSITS. 175 
 
 When urinary deposit is examined with the microscope, it 
 will be found either crystalline, amorphous, or organized. 
 When, as is frequently the case, the deposit consists of a 
 mixture of different forms, each of them in succession should 
 be examined, until the nature of the whole deposit is clearly 
 understood. 
 
 CRYSTALLINE DEPOSITS will probably be either uric acid, 
 pMfesphate of lime and magnesia (from which the triple phos- 
 phate is formed), oxalate of lime, or perhaps cystine. 
 
 Triple Phosphate. This salt (called also the double phos- 
 phate of ammonia and magnesia) is formed by supersaturating 
 with ammonia. . Phosphate of lime is also precipitated by the 
 same means, but may be distinguished by the microscope. 
 The crystals of the triple phosphate are stellate or triangular 
 prisms, as seen in Fig. 54. They disappear on the addition 
 of acetic acid. 
 
 Uric (or Lithic) Acid. This salt, like the earthy phos- 
 phates, exists in a small quantity in healthy urine, but as the 
 proportion varies considerably in many forms of disease, its 
 determination when in abnormal quantity affords much assis- 
 tance in diagnosis. 
 
 It is insoluble in alcohol, and nearly so in dilute hydro- 
 chloric and sulphuric acid ; but it combines with the alkalies, 
 forming salts, which are insoluble or very sparingly soluble in 
 water. 
 
 The action of nitric acid upon uric acid is characteristic. It 
 will gradually dissolve it, carbonic acid and nitrogen being 
 given off with effervescence, leaving behind a mixture of 
 alloxan (C 8 N 2 H 4 O 10 ), alloxantine (C 4 H 3 N 5 O s ), and other 
 compounds. This may be evaporated nearly to dryness, when 
 a red residue will be left, which, when cold, should be moist- 
 ened with ammonia, which will develope a beautiful purple 
 color, owing to the formation of murexide (C 13 N 5 H 8 ). 
 
176 
 
 THE MICROSCOPIST. 
 
 The crystalline forms of uric acid are various, but appear to 
 be modifications of the rhombic prism. 
 
 Fig. 54. 
 
 Fig. 55 represents some of its forms. 
 
 Oxalate of Lime often exists in the form of minute octahe- 
 dral crystals, varying from ? Joth to .gg^th of an inch in 
 diameter, a, Fig. 56. When allowed to dry on the glass, each 
 
EXAMINATION OF URINARY DEPOSITS. 177 
 
 crystal appears under the microscope like a black cube, having 
 
 Fig. 55. 
 
 in the centre a small white square opening, as shown at 
 
178 
 
 THE MICROSCOPIST. 
 
 This is owing to the rays of light being mostly refracted be- 
 yond the field of vision. On again moistening them, the crys- 
 tals reappear in their octahedral form. Sometimes this salt 
 
 assumes the forms represented at c, more or less resembling 
 dumb-bells.* This forrn ; like the crystals of uric acid, the 
 
 * Dr. Fricke, in the American Journal of Medical Science, July, 
 1850, states as his opinion that the dumb-bell forms of crystals are 
 not oxalate of lime, but disintegrated crystals of uric acid. 
 
EXAMINATION OP URINARY DEPOSITS. 179 
 
 triple phosphate, &c., is beautifully colored when examined 
 by polarized light; the octahedral variety has little or no effect 
 upon it, being invisible, or nearly so, when the field is dark. 
 If the " dumb-bells" are kept in liquid for any length of time, 
 they gradually pass into octahedra. 
 
 As the crystals of oxalate of lime are very transparent, and 
 about the same specific gravity as the urine, they may readily 
 escape detection, unless some considerable time is allowed for 
 deposition, or the urine is passed through a filter. 
 
 Oxalate of lime is insoluble in water, in acetic and oxalic 
 acids, and in solution of potash; but it is readily soluble in 
 dilute nitric and hydrochloric acids. 
 
 Cystine has occasionally been found as a crystalline deposit 
 and in the form of small calculi. It may be distinguished by 
 being insoluble, or nearly so, in water and dilute acids, but 
 soluble in ammonia, from which small hexagonal crystals are 
 deposited on evaporation. The usual microscopic appearance 
 is represented at a, Fig. 57. At b is the form left from the 
 ammoniacal solution. 
 
 Fig. 57. 
 
 oW (J) 
 
 g>O 
 
 o" i 
 
 AMORPHOUS DEPOSITS consist probably of phosphate of 
 lime, urate of ammonia, urate of soda, fat, or chylous matter. 
 
 Phosphate of Lime. This salt has already been described as 
 existing in urine in conjunction with the phosphate of magnesia. 
 It is thrown down, together with the triple phosphate (before 
 
180 THE MICROSOOPIST. 
 
 noticed), on the addition of ammonia. The crystalline shape 
 of the triple phosphate, however, readily distinguishes it under 
 the microscope from the amorphous particles of phosphate of 
 lime with which it is usually mixed. The earthy phosphates 
 are readily soluble in dilute acids, from which they are pre- 
 cipitated by ammonia. They are insoluble in a solution of 
 potash. 
 
 Urate of Ammonia constitutes one of the most common 
 urinary deposits. It is gradually deposited as the urine cools, 
 in the form of an amorphous precipitate, which, with a high 
 magnifying power, appears to consist of minute rounded par- 
 ticles, occasionally adhering together, frequently mixed with 
 small crystals of uric acid, and occasionally with the earthy 
 phosphates. A deposit of urate of ammonia readily dissolves 
 when the urine containing it is gently warmed, and is preci- 
 pitated again when the liquid cools. (The earthy phosphates 
 and uric acid are nearly as insoluble in hot as cold water.) 
 
 When urate of ammonia is treated with dilute acetic or 
 hydrochloric acid, it is decomposed, and uric acid, is formed. 
 
 Urate of Soda is often met with in the urine of patients 
 taking medicinally the carbonate or other salts of soda. It re- 
 sembles the urate of ammonia in being soluble in hot water, 
 and in most of its chemical characters, but may be generally 
 recognised without difficulty under the microscope, forming 
 minute globular or granular aggregations, with, occasionally, 
 irregular and curved protuberances. 
 
 Fat may be recognised by the particles being minute round 
 globules, with dark and well-defined outlines, which dissolve 
 when agitated with ether. 
 
 Sometimes this substance is mixed with albuminous matter, 
 forming a kind of emulsion, so that no trace of fat can be per- 
 ceived with the microscope. In such cases, the urine may be 
 agitated with a little ether, which will dissolve the fat, and 
 
EXAMINATION OF URINARY DEPOSITS. 181 
 
 the solution so formed will separate from the watery liquid, 
 and form a distinct stratum on the surface. 
 
 Chylous Matter may be known by the urine being opaque 
 and milky in appearance, yielding fatty matter when agitated 
 with ether, and containing minute, amorphous, albuminous 
 particles, and perhaps also colorless globules, which may 
 possibly be mistaken for oil globules, from which their insolu- 
 bility in ether distinguishes them. 
 
 ORGANIZED DEPOSITS may either be mucus, usually mixed 
 with epithelium ; pus ; blood ; or semen. 
 
 Mucus. If the particles observed with the microscope are 
 round, or nearly so, and granulated on the surface, entangled 
 in tenacious, stringy masses, which do not break up and mix 
 uniformly with the liquid on agitation, it is probably mucus. 
 
 Epithelial debris may be recognised by the peculiar form of 
 its particles. Mucous urine generally contains a considerable 
 amount of earthy phosphates and other matters. 
 
 Pus may be known by the particles not being held together 
 by any tenacious matter, but floating freely in the liquid. The 
 granules of pus and mucus present almost the same appearance 
 under the microscope, although the latter may probably be 
 rather smaller and less distinctly granular. Acetic acid renders 
 the interior nuclei visible in both, but it coagulates the fluid 
 portion of the mucus. 
 
 Even this test may be uncertain, on account of the dilution 
 of the mucous fluid, and also because the coagulation may have 
 been already occasioned by the presence of the large quantity 
 of water. When the quantity of mucus is abundant, however, 
 this test will be sufficient. 
 
 Blood. When this is suspected in the urine, it may be 
 examined under the microscope for any blood corpuscles that 
 may be in it. If the blood has coagulated, they will probably 
 be entangled in the coagula, and may be forced out by gentle 
 
 16 
 
182 THE MICRO SCO PI ST. 
 
 pressure under a strip of thin glass. If there is no coagula, 
 the liquid may rest for a short time, and a drop from the bot- 
 tom examined. The urine may also be tested for albumen after 
 separating the solid matter by filtering. When the coloring 
 matter of the blood is present, it will coagulate with the albu- 
 men, giving it a red or brown color. When the fibrin, in its 
 soluble form, is present, it usually coagulates spontaneously on 
 cooling, causing the urine to become gelatinous. The coagulum 
 of fibrin, when pressed between glasses, is generally composed 
 of minute amorphous particles, with a few red blood corpuscles, 
 quite different from the granular mucus corpuscles, for which it 
 might be mistaken without microscopic examination. 
 
 Bile or purpurine in urine has nearly the same color as when 
 blood is present; hence, unless the blood corpuscles are present, 
 we should apply the tests for the detection of those substances 
 before finally deciding. Purpurine will be dissolved by treat- 
 ing with warm alcohol, or may be precipitated by adding a 
 little warm aqueous solution of urate of ammonia, which on cool- 
 ing will fall down, carrying with it the coloring matter. Bile 
 may be tested by pouring a few drops of urine on a white 
 plate, and adding carefully a drop or two of nitric acid. When 
 bile is present in any considerable quantity, the liquid becomes 
 successively pale-green, violet, pink, and yellow, the color 
 rapidly changing as the acid mixes with the urine. When 
 only slight traces of bile are. present, the urine should be con- 
 centrated by evaporation. 
 
 When semen is present in urine, it may easily be detected 
 under the microscope, by the appearance of minute animalcu- 
 les, always found in the spermatic fluid, and hence called sper- 
 matozoa. They are oval in shape, with long and delicate tails. 
 Traces of albumen may generally be detected in urine contain- 
 ing semen. 
 
EXAMINATION OF URINARY DEPOSITS. 183 
 
 DIABETIC AND ALBUMINOUS URINE. Albumen may be 
 tested by boiling the suspected urine gently in a test-tube, 
 when it will be coagulated. As, however, a white precipitate 
 results on boiling, from an excess of earthy phosphate, it will 
 be necessary to add a few drops of nitric acid, which will re- 
 dissolve the phosphates but leave the coagulated albumen un- 
 affected. Nitric acid also will coagulate albumen. If both 
 heat and nitric acid throw down a white precipitate from urine 
 in separate portions, there can be no doubt of the presence of 
 albumen. 
 
 The peculiar casts of urinary tubes found in the urine of 
 patients suffering from Bright' s disease, consist of fibrinous or 
 albuminous matter and entangling'blood-corpuscles, epithelium, 
 and fatty globules. 
 
 Diabetic Sugar has the same chemical composition as that 
 contained in most kinds of fruit, known as grape sugar. Se- 
 veral tests have been proposed for its detection in urine. 
 
 Trommer's Test is founded on the circumstance that when a 
 solution of diabetic or grape sugar is boiled with a mixture of 
 potash and sulphate of copper, the oxide of copper contained 
 in the latter is reduced to the state of suboxide, which is pre- 
 cipitated in the form of a reddish-brown or ochre-colored 
 granular powder. 
 
 Moore's Test is made by mixing a little suspected urine with 
 half its volume of liquor potassse and boiling gently for about 
 five minutes. If sugar is present, the liquid assumes a brown 
 or bistre tint. 
 
 The Fermentation Test is made by filling a test-tube with 
 the suspected urine, to which a little yeast has been added. 
 The tube is then inverted over a saucer containing some of the 
 urine, and set aside in a warm place for about twenty-four 
 hours. If sugar is present it undergoes the vinous fermenta- 
 tion, by which it becomes converted into alcohol and carbonic 
 
184 THE MICROSCOPIST. 
 
 acid. The latter rises in the tube and displaces the liquid. If 
 no sugar be present, no fermentation will take place, and no 
 gas will be formed in the tube. 
 
 Test from the Growth of the Torula. During the process of 
 the vinous fermentation of a liquid containing sugar, a delicate 
 white scum collects on the surface, which when examined with 
 a magnifying power of four or five hundred diameters, will be 
 found to consist of small, oval vesicles, a, Fig. 58, which, in 
 
 Fig. 58. 
 
 O 
 
 
 
 i> & 
 
 % 
 * > fo % . 
 
 
 
 
 
 ir*a 
 
 % 
 
 the course of a few hours, rapidly change their form, becoming 
 longer and more tubular, and give rise to new vesicles, which 
 shoot out from the parent body, forming an irregular jointed 
 confervoid stem, 6. These again break up into a great num- 
 ber of oval vesicles, which separate, and fall to the bottom, 
 where they may be detected by the microscope. 
 
 The following tables for facilitating the examination of 
 urine and urinary deposits, are modified from Bowman's Me- 
 dical Chemistry. The reader may also consult the Manuals of 
 Drs. Golding Bird, Griffith, Markwick, and Rees. The works 
 of the latter three gentlemen have been published in Philadel- 
 phia, in one convenient volume. The "Analysis" of Dr. Rees 
 contains also a valuable essay on the treatment of urinary dis- 
 
EXAMINATION OF URINARY DEPOSITS. 185 
 
 TABLE I. 
 
 FOR THE CHEMICAL EXAMINATION OF URINARY 
 DEPOSITS. 
 
 1. The sediment dissolves when warmed. Urate of Am- 
 monia. 
 
 2. Not soluble when warmed, but soluble in acetic acid. 
 Earthy Phosphates. 
 
 3. Insoluble in acetic, but soluble in dilute hydrochloric 
 acid. Oxalate of Lime. 
 
 4. Insoluble in dilute hydrochloric acid. Purple with nitric 
 acid and ammonia. Uric Acid. 
 
 If neither of these, it may be, 
 
 5. Greenish-yellow deposit, easily diffused on agitation. 
 
 6. Ropy and tenacious. Mucus ? 
 
 7. Red or brown; not soluble when warmed; the fluid por- 
 tion coagulable by heat and nitric acid. Blood ? 
 
 8. Soluble in ammonia; the solution leaving, on evaporation, 
 hexagonal crystals. Cystine f 
 
 9. Yellowish sediment, soluble when warmed. Urate of 
 Soda f 
 
 10. Ether yields, after agitation, an oily or fatty residue. 
 Fatty Matter. 
 
 11. Milky appearance. Chylous Matter. 
 
 TABLE II. 
 
 FOR THE EXAMINATION OF THE CLEAR LIQUID 
 PORTION. 
 
 1. Crystals with nitric acid. Excess of Urea. 
 
 2. Fermentation, or Trommer's test. Sugar. 
 
 16* 
 
186 THE MICEOSCOPIST. 
 
 3. Precipitate formed on boiling; soluble in nitric acid. 
 Excess of Earthy Phosphates. 
 
 4. Precipitate formed on boiling ; insoluble in nitric acid. 
 Albumen. 
 
 5. Precipitate formed by nitric acid. Excess of Uric Acid, 
 or Albumen. 
 
 6. Concentrated urine yields needle-shaped crystals with 
 hydrochloric acid. Hippuric Acid. 
 
 If the urine is highly colored, 
 
 7. Dark coagulum formed on boiling. Blood ? 
 
 8. Red color with hydrochloric acid. Excess of Coloring 
 Matter. 
 
 9. Pink precipitate with warm solution of urate of ammonia. 
 Purpurine. 
 
 10. Change of color with nitric acid. Biliary Matter. 
 
 TABLE III. 
 
 FOR MICROSCOPICEXAMINATION OF DEPOSIT. 
 If Crystalline. 
 
 1. Lozenge-shaped, &c. Uric Acid. 
 
 2. Stellas, or three-sided prisms (after saturating with am- 
 monia). Triple Phosphate. 
 
 3. Octahedra, or dumb-bells. Oxalate of Lime. 
 
 4. Rosette-like tables. Cystine. 
 
 If Amorphous. 
 
 5. Soluble when warmed. Urate of Ammonia. 
 
 6. Soluble in acetic acid. Phosphate of Lime. 
 
 7. Yellowish grains. Urate of JSoda ? 
 
EXAMINATION OF URINARY DEPOSITS. 187 
 
 8. Round globules with dark edges. Fatty Matter. 
 
 9. White and milky. Chylous Matter ? 
 
 If Organized. 
 
 10. Granulated corpuscles, in stringy aggregations. Mucus. 
 
 11. Irregularly shaped scales. Epithelium. 
 
 12. Detached granulated corpuscles. Pus. 
 
 13. Blood-corpuscles. Blood. 
 
 14. Spermatozoa. Semen. 
 
CHAPTER XIII. 
 
 ON POLARIZED LIGHT. 
 
 " IF we transmit/' says Dr. Brewster, " a beam of the sun's 
 light through a circular aperture into a dark room, and if we 
 reflect it from any crystallized or uncrystallized body, or trans- 
 mit it through a thin plate of either of them, it will be re- 
 flected and transmitted in the very same manner and with the 
 same intensity, whether the surface of the body is held above 
 or below the beam, or on the right side or left, or on any other 
 side of it, provided that in all these cases it falls upon the 
 surface in the same manner, or, what amounts to the same 
 thing, the beam of solar light has the same properties on all 
 its ,'ides; and this is true, whether it is white light as directly 
 emitted from the sun, or whether it is red light, or light of 
 any other color. 
 
 " The same property belongs to light emitted from a candle, 
 
 Me. 
 
 or any burning or self-luminous body, and all such light is 
 called common light. A section of such a beam of light will 
 
ON POLARIZED LIGHT. 189 
 
 be a circle, like A, B, C, D, Fig. 59, and we shall distinguish 
 the section of a beam of common light by a circle with two 
 diameters, A B, CD, at right angles to each other. 
 
 " If we now allow the same beam of light to fall upon a 
 rhomb of Iceland spar, as in Fig. 60, and examine the two 
 
 circular beams, o } E e, formed by double refraction, we shall 
 find, 
 
 " 1. That the beams o, E e, have different properties on dif- 
 ferent sides ; so that each of them differs, in this respest, from 
 the beams of common light. 
 
 " 2. That the beam o differs from E e in nothing, excepting 
 that the former has the same properties at the sides A' and B' 
 that the latter has at the sides C' and D', as shown in Fig. 59 ; 
 or, in general, that the diameters of the beam, at the extremi- 
 ties of which the beam has similar properties, are at right 
 angles to each other. 
 
 " These two beams, o, E e, Fig. 60, are therefore said to 
 be polarized, or to be beams of polarized light, because they 
 have sides or poles of different properties. 
 
 " Now it is a curious fact, that if we cause the two polarized 
 beams, O o, E e, Fig. 60, to be united into one, we obtain a 
 beam which has exactly the sajme properties as the beam A, B, 
 
190 THE MICROSCOPIST. 
 
 C, D, Fig. 59, of common light. Hence we infer, that a beam 
 of common light consists of two beams of polarized light, 
 whose planes of polarization, or whose diameters of similar 
 properties, are at right angles to one another." 
 
 There are other means of polarizing light besides that of 
 double refraction, just mentioned. M. Malus discovered, in 
 1810, that a beam of common light, reflected from glass at an 
 angle of 56, or from water at an angle of 53 became polar- 
 ized. 
 
 In order to explain the phenomena of polarized light when 
 produced by reflection from glass, let C, D, Fig. 61, represent 
 
 Fig. 61. 
 
 T> 
 
 two tubes, one turning within the other. A, B, are plates of 
 glass capable of turning on their axis, so as to form different 
 angles with the axis of the tube. 
 
 If a beam of light, r s, from a candle or hole in the window- 
 shutter, fall upon A at the polarizing angle of 56 45', it will 
 be reflected through the tubes, and will fall upon the second 
 plate, B, also at an angle of 56 45'. If, however, this plate 
 be so placed that its plane of reflection is at right angles to 
 the plane of reflection of the first plate, A, the ray of light 
 will not suffer reflection from B, or will be so fainb as to be 
 scarcely visible. If we now turn round the tube, D, carrying 
 the plate, B, without moving the tube C, the reflected ray, E, 
 
ON POLARIZED LIGHT. 191 
 
 will become brighter and brighter till the tube has been turned 
 round 90, when the plane of reflection from B is coincident with 
 and parallel to that from A. In this position the reflected ray, E 
 is brightest. If the tube be turned again, the light will grow 
 more and more faint, until another 90 are arrived at, when it 
 will again undergo reflection. Thus, changes will take place in 
 every quadrant of 90 until the starting-point is again reached, 
 the ray of light being alternately faint and visible. 
 
 The same effect will be produced if we cause a ray of light, 
 R, Fig. 62, to pass through bundles of glass plates, A, B, in- 
 
 clined at the proper angle. If the bundle of plates, B, be 
 placed as [in the figure, the ray s >, polarized by passing 
 through the bundle, A, will be incident on B at the polarizing 
 angle, and not a particle will be reflected, but it will be trans- 
 .mitted, as seen at v w. If B is now turned round its axis, 
 the transmitted light, v w, will gradually dimmish, and more 
 and more light will be reflected by the plates of B, till, after 
 a rotation of 90, the ray, v w, will disappear, and all the 
 light will be reflected. Alternate transmissions and reflections 
 will thus take place in every quadrant, as in the former case. 
 For the ray passing through the tube in Fig. 61, or the ray, 
 s r, in the last figure, we may substitute one of the polarized 
 rays formed by double refraction in a rhomb of Iceland spar, 
 as seen in Fig. 60, or we may employ with even greater ad- 
 vantage the single image prism of Mr. Nicol, who employed a 
 rhomb of calcareous spar divided into two equal portions, in a 
 plane passing through the acute lateral angles, and nearly 
 
192 THE MICROSCOPIST. 
 
 touching the obtuse solid angles. The cut surfaces having been 
 carefully polished, were then cemented together with Canada 
 balsam, so as to form a rhomb of nearly the same size and 
 shape as it was before cutting. 
 
 By this arrangement, of the two rays into which a beam of 
 common light would be separated, only one is transmitted, the 
 other being rendered too divergent. Two of these prisms form 
 the usual polarizing apparatus of the microscope, being used in 
 the same manner as the bundles of glass plates, Fig. 62, just 
 described. One of the prisms is adapted to the under surface 
 of the stage, and is called the polarizer ; the other, called the 
 analyzer, is placed above the eye-glass. 
 
 Dr. Brewster recommends that the analyzing prism be placed 
 immediately behind the object-glass, next the eye, having a 
 rotation independent of the body of the microscope. 
 
 Another method of polarizing light, is to disperse or absorb 
 one of the oppositely-polarized beams which constitute common 
 light, and leave the other beam polarized in one plane. These 
 effects may be produced by thin plates of agate, tourmaline, 
 &c. 
 
 Many persons employ a thin plate of tourmaline as an 
 analyzer in place of a Nicol's prism, and if its color be not 
 objectionable, it may be used to advantage, as the field of 
 view is not so much contracted as when a prism is used. A 
 tourmaline of a neutral tint is an excellent analyzer. 
 
 The splendid colors, and systems of colored rings produced 
 by transmitting polarized light through transparent bodies that 
 possess double refraction, are the most brilliant phenomena 
 that can be exhibited. They were discovered simultaneously 
 by M. Arago and Dr. Brewster. 
 
 To see these colors : having the polarizing apparatus so 
 placed that no light can be seen through it, place a thin film 
 ofynica or sulphate of lime (between the twentieth and fiftieth 
 
ON POLARIZED LIGHT. 193 
 
 of an inch thick), so that the polarized beam may pass through 
 it perpendicularly. It should be placed between the polarizer 
 and the analyzer, as on the stage of the microscope. If now 
 the eye is applied to the polarizing apparatus, as before, the 
 surface of the film of sulphate of linie, &c., will be seen 
 covered with the most brilliant colors. If the film be turned 
 round, still keeping it perpendicular to the polarized ray, the 
 colors will become less or more bright, and two positions will 
 be found, at right angles with each other, wherein no colors 
 at all are perceived. If the analyzer be turned round, the film 
 retaining its position, complementary colors will alternate, 
 together with points of invisibility, during each revolution. 
 
 The colors of the film vary with its thickness, so that by 
 making grooves or lines of various depths, the most beautiful 
 patterns may be produced. Drawings of figures and land- 
 scapes are thus executed, and being mounted between glasses 
 in Canada balsam, are invisible, or nearly so, till exposed to 
 polarized light, when they are seen distinctly, arrayed in most 
 gorgeous colors. 
 
 Various crystals exhibit, round their axes of double refrac- 
 tion, beautiful systems of colored rings, often intersected by 
 a black cross. Complementary colors may be produced in 
 them by turning round the analyzer. In large crystals, as 
 rhombs of Iceland spar, certain angles must be ground down 
 and polished in order to exhibit the rings. 
 
 In those crystals having two axes of double refraction, a 
 double system of rin^ will be seen. A transverse section of 
 a prism of nitre will exhibit this phenomenon. 
 
 The great advantage of employing the microscope in viewing 
 the colors of crystals, &c., by polarized light, arises from the 
 fact that, when crystallized on a slip of glass, many of the 
 small crystals will be arranged with their axes of double re- 
 fraction in the direction of the polarized beam. All such, 
 
 17 
 
194 THE MICBOSCOPIST. 
 
 therefore, will exhibit colors, as will those also in which the 
 thickness of the crystal is not below the proper standard. 
 
 After the polarizing apparatus is adjusted, as before de- 
 scribed, the crystals properly mounted may be placed on the 
 stage, in the same way as ordinary objects. Some few vege- 
 table structures may be exhibited in the same manner, as the 
 siliceous cuticle of equisetum, starch, &c. Many animal 
 structures, as feathers, slices of quill, horn, &c., are best shown 
 by placing a film of selenite or mica beneath them, by which 
 they become intensely colored. If the film be of unequal 
 thickness, the colors will vary, 
 
 "The application," says Mr. Quekett, "of this modification 
 of light to the illumination of very minute structures has not 
 yet been fully carried out, but still there is no test of diffe- 
 rences in density between any two or more parts of the same 
 substance that can at all approach it in delicacy. All struc- 
 tures, therefore, belonging either to the animal, vegetable, or 
 mineral kingdom, in which the power of unequal or double 
 refraction is suspected to be present, are those that should es- 
 pecially be investigated by polarized light. Some of the most 
 delicate of the elementary tissues of animals, such as the tubes 
 of nerves, the ultimate fibrillas of muscle, &c., are amongst 
 some of the most striking subjects that may be studied with 
 advantage under this method of illumination." 
 
 To prepare Crystals for Polarized Light. Pour a few 
 drops of a saturated solution of the salt on a glass slide, 
 gently warm it over a spirit lamp, so^s to evaporate the 
 excess of fluid, taking care not to apply too much heat, lest 
 the water of crystallization be driven off and the salt become 
 opaque. The more slowly the crystallization is effected, the 
 better. 
 
 The crystals should then be examined, and the best of them 
 mounted, either in the dry way (interposing a cell of paper, 
 
ON POLARIZED LIGHT. 195 
 
 &c. 7 to preserve them from injury by the pressure of the glass 
 cover), or in Canada balsam. If it be desired to examine the 
 crystals during their formation, the crystallization should be 
 carried on in a glass that is slightly concave. All those crys- 
 tals that are so thin as not to exhibit color, may have color 
 given them by placing a film of mica or selenite under them 
 on the stage of the microscope. 
 
 According to Mr. Fox Talbot, who first applied the micro- 
 scope to the examination of polarized light, sulphate of copper, 
 crystallized from a solution to which a little nitric ether has 
 been added ; oxalate of chromium and potash, from an aqueous 
 solution ; and borax, crystallized in dilute phosphoric acid, are 
 especially beautiful. 
 
CHAPTER XIV. 
 
 MISCELLANEOUS HINTS TO MIC B SO P I S T S. 
 
 . 
 
 ON CLEANING THE GLASSES. " When you clean the eye- 
 glasses (a point of great importance to pure vision), do not 
 remove more than one at a time, and be sure to replace it be- 
 fore you begin another ; by this means you will be sure to 
 preserve the component glasses in their proper places ; recol- 
 lect that if they become intermingled, they will be useless. 
 Keep a piece of well-dusted chamois leather, slightly impreg- 
 nated with some of the finest putty or crocus powder, in a little 
 box to wipe them with for it is of consequence to preserve it 
 from dust and damp ; the former will scratch the glasses, and 
 the latter will prevent you from wiping them clean. As to the 
 object-glasses, endeavor to keep them as clean as possible 
 without wiping, and merely use a camel's-hair pencil to brush 
 them with ; for wiping them hard with anything has always a 
 tendency to destroy their adjustment, unless they are firmly 
 burnished into their cells." Dr. Goring. 
 
 ON STOPPING FALSE LIGHT IN MICROSCOPES. This is one 
 of the most important requisites in an instrument; for however 
 perfect it may be, if there is the least light reflected from the 
 mountings of the glasses, or within the tubes, the fog and glare 
 produced will materially deteriorate their performance ; it is 
 therefore necessary that all their surfaces be made as sombre as 
 possible. The usual method of effecting this is to cover the 
 parts while hot with a black lacquer, made by mixing lamp- 
 
MISCELLANEOUS HINTS TO MICRO SCOPISTS. 197 
 
 black in a solution of shell-lac in strong spirits of wine. A 
 more elegant method, and better suited for delicate work, is to 
 wash the surface, previously freed from grease and tarnish, with 
 a solution of platina in nitro-muriatic acid (chloride of plati- 
 num) ; after remaining on the work a few minutes it is wiped off, 
 the surface having assumed a deep brown or black color. If 
 these are not at hand, a strong solution of muriate of ammonia 
 will answer for temporary purposes. Another method of sti- 
 fling false light is by stops or diaphragms in the body of the in- 
 strument ; these have already been referred to. 
 
 CABINET FOR MICROSCOPIC OBJECTS. The author of " Mi- 
 croscopic Objects" recommends a cabinet with shallow drawers 
 twelve of them occupy a depth of four and a half inches 
 the most convenient width from front to back being six inches. 
 Into these shallow drawers the slides containing the objects are 
 laid flat in double rows. The outer ends of the slides are 
 made to fit into a ledge in the front and back of each drawer. 
 The inner ends of the slides meeting in the middle of the 
 drawer are kept down by a very thin slip of wood covered with 
 velvet. In this way the slides do not shake when the cabinet 
 is moved from place to place ; every object is seen without 
 removal, and no loss of time is occasioned in making a selec- 
 tion. 
 
 Some persons have their slides arranged edgewise, in boxes 
 made in imitation of books ; the ends of the slides being held 
 by a sort of rack. This sometimes may be convenient, but the 
 other form is preferable. 
 
 GOADBY'S MANIPULATING Box. This is an exceedingly 
 neat and useful article, represented by Fig. 63. No. 1, repre- 
 sents the box when open, No. 2, a movable tray of peculiar 
 form, and No. 3, the box with No. 2 removed. 
 
 " No. 1. a. Compartment to receive a bottle, 2 inches square, 
 3J high, to the top of the stopper, for preserving fluid. I. 
 
198 
 
 THE MICROSCOPIST. 
 
 Space reserved for the spirit lamp. c, c. A shelf of tin, perforat- 
 ed with six holes, to receive three stoppered, two-drachm bottles, 
 for liq. potassse, sulphuric acid, carnphene (or turpentine), and 
 
 Fig. 63. 
 
 three glass jars, 2f ths high, Iths diameter, made out of stout 
 glass, without a lip, and fitted with corks, for Canada balsam, 
 prepared asphaltum, lamp-black and gold size. d. A slab of 
 porcelain, 2fths square, resting upon a tin frame, and carried up 
 so as to be flush with the level of all the bottles, and the tray 
 (2), when in its place. Beneath the slab is e, a drawer, 2f ths 
 long, 2i wide, and f ths deep, to hold about three dozen of the 
 smallest slides I use, viz., 2th by f ths. Beneath e is a deep 
 well, which occupies the space from the drawer e to/, another 
 drawer, which runs the whole length of the box, from front to 
 back ; it has the width and depth of e. 
 
 No. 2. g 1 . This compartment of the tray measures 8 inches 
 long, 2 full wide, li deep. It contains the iron plate, its 
 brass legs, and mahogany stand ; a small cutting-board, kept for 
 thin glass only, measuring 6 inches by 2fths, -Jth thick, fur- 
 
MISCELLANEOUS HINTS TO MICRO S C OP I ST S. 199 
 
 nished with a guide-board 5 inches long, inch wide, and |th 
 thick, and a gauge, 6 inches long, nearly | ths wide, and fth 
 thick. A card-board box, 2 by If ths, and f ths deep, to hold 
 plates of thin glass; the small brass square, already described; 
 mahogany square, 6 inches by 2J, ith thick; a number of 
 badger' s-hair pencils in handles. g z . Glazier's diamond; scratch 
 do.; marine glue (cane) brush; knife and engraver's tool for 
 cleaning cells ; small glass mules to grind the black cement on 
 the porcelain slab, and sundry glass (dropping and other) 
 tubes. g*. Pill-box with whiting; white wax for thread; cot- 
 ton-wool; sundries. 
 
 No. 3. h. A fixed tray, 4 inches by 2 J, and fths deep, to 
 contain glass for covers to larger cells. i. A well, 5 by 4 
 inches, 1 full deep, to hold spare slides of the larger size, 
 with or without cells cemented to them, spare cells, &c. k. 
 A supply of the finest and other varieties of China three twist; 
 pill-box containing small pins, so necessary in dissecting j pill- 
 box containing cells cut in the thinnest glass. Drawer/, con- 
 tains several small palette-knives, in ivory handles, for mixing 
 the cement on the slab ; the blades differ in length from 1 J to 
 3ith, and from ith to fths at the point; drills for glass and 
 many little things. Below the shelf c c, is a similarly perfo- 
 rated shelf, raised somewhat from the bottom, the design being 
 to grasp the bottles at two points. Should the bottles not be 
 sufficiently high to occupy all the depth allowed for them, they 
 must be raised by a shelf of tin, the intention being, that when 
 the box is closed, everything should be more or less pressed 
 upon and kept in its place. The whole is japanned dead black 
 within, and lustrous black without." 
 
 BREWSTER'S METHOD OP ILLUMINATING OBJECTS. Con- 
 sidering a perfect microscope as consisting of two parts, viz., 
 an illuminating apparatus, and a magnifying apparatus, Sir D. 
 Brewster states, that it is of more consequence that the illumi- 
 
200 THE MICROSCOPIST. 
 
 nating apparatus should be perfect, than that the magnifying 
 one should be so ; and the essential part of his method consists 
 in this : That the rays which form the illuminating image or 
 disk shall have their foci exactly on the part of the microscopic 
 object to be observed, so that the illuminating rays may radiate 
 as it were from the object, as if it were luminous. Now this 
 can only be well attained by illuminating with a single lens, 
 or a system of lenses, without spherical or chromatic aberra- 
 tion, whose focal length, either real or equivalent, is less than 
 the focal length of the object-glass of the microscope. The 
 smaller the focal length of the illuminating lens, or system of 
 lenses, the more completely do we secure the condition, that 
 the illuminating rays shall not come to a focus, either before 
 they reach the object, or after they have passed it. 
 
 MODE or OBTAINING THE WHEEL ANIMALCULE (Vortir 
 cella fotatorla). '" Early in the spring I fill a three-gallon jug 
 with pure rain-water (not butt-water, because it contains the 
 larvae of the great tribe). This quantity more than suffices to 
 fill a half-pint mug, and to keep it at the same level during the 
 season. I then tie up a small portion of hay, about the size 
 of the smallest joint of the little finger, trimming it so that it 
 may not occupy too much room in the mug, and place it in the 
 water ; or about the same quantity of green sage leaves, also 
 tied and trimmed. About every ten days I remove the decay- 
 ed portion with a piece of wire, and substitute a fresh supply. 
 A much greater number of animalcules are raised by the sage 
 leaves ; but I have sometimes been obliged to discontinue the 
 use of it, on account of its producing mouldiness. I take them 
 out with an ear-picker, scraping up the sides of the mug near 
 the surface (including the dirt which adheres to them by the 
 tail), or under the hay or sage/' J. Ford. 
 
 SUBSTITUTE FOR THE CONCAVE SPECULUM. Mr. G-. Jack- 
 son employs a plano-convex lens of about two inches in diame- 
 
MISCELLANEOUS HINTS TO M I CRO SCOPI S T S. 201 
 
 ter, and of four and a half inches focus, silvered on the plane 
 slide, and backed with a plate of brass. This lens, when so 
 treated, becomes a reflector of about two and a quarter inches 
 focus, and forms one of the best instruments that can be desir- 
 ed for throwing light upon an object viewed as opaque. We 
 have used such arrangement for some time in place of the con- 
 cave mirror, and deemed it peculiar to ourselves till reading an 
 account of the above. 
 
 APPARATUS TO PREVENT THE EVAPORATION OP LIQUIDS 
 UNDER THE MICROSCOPE. Vapors arising from the liquids 
 under observation would, by condensing on the under surface 
 of the object-glass, form there round drops, which act as so 
 many lenses, and which, arresting the rays of light in their 
 progress, would scatter them in every direction, and thus com- 
 pletely destroy the image before it could reach the object-glass. 
 This effect takes place not only when the temperature of the 
 liquid is raised by the application of heat, either directly or 
 in consequence of chemical action, but also when, in studying 
 any body by the microscope, a fuming acid is used, such as 
 the hydrochloric. This inconvenience is prevented by en- 
 closing the frame of the object-glass in a small glass tube, shut 
 at one end, whose inner surface is closely applied to the surface 
 of the object-glass. This end is then plunged into the liquid, 
 which is thus prevented from either beclouding the surface of 
 the lens or finding its way into the interior of the microscope 
 and there producing the same effect. RaspaiVs Organic 
 Chemistry. 
 
 DROPPING TUBES, for placing on the object-holder or slide 
 any reagent whose action is to be examined, may be easily 
 made by softening a piece of glass tube in the flame of a lamp, 
 and drawing it out till it becomes capillary, after which it may 
 be broken to a convenient length. Fishing- tubes for animal- 
 may also be made in the same way. 
 
INDEX. 
 
 PACK 
 
 Achromatic object-glasses, their invention an epoch in histology, 18 
 description of, ... 34 
 
 comparison of different makers, 38 
 
 Animal tissues, to be examined when fresh, . . .17 
 
 on procuring, . . . . 81 
 
 Accessory instruments, . ..... 41 
 
 Animalcules cage, ...... 37, 49 
 
 Asphaltum cement, . . . ; . . 60 
 
 Agate, ....... 67 
 
 Algse, . 77 
 
 Aphides, ....... 90 
 
 Acari, . . . . . . . .90 
 
 Anatomical preparations, ..... 94 
 
 Areolar tissue, ....... 103 
 
 Artificial star, as a test object, .... Ill 
 
 Angle of aperture, explained, ..... 112 
 
 Arm rests, ....... 120 
 
 Albuminous urine, . . . . . 170, 183 
 
 Alkaline salts in urine, . . . . . 173 
 
 Advantage of polarized light in examination, . . . 193 
 
 Apparatus to prevent evaporation, .... 201 
 
 B. 
 
 Bog iron ore, from infusoria, . . . . .14 
 
 Borelli, his observations on pus, &c., . . . 15 
 
 Blood corpuscles, . . . . . .95 
 
204 INDEX. 
 
 PAGE 
 
 Blood disks of siren, . . . . . .. 95 
 
 Bone, . , . . . . . . ' . --ijdr 
 
 Basement membrane, ..... 104, 131 
 
 Bat's hair, . . . . . . .114 
 
 Branchial cartilage of tadpole, .... 135 
 
 Blood in urine, ...... 169,181 
 
 Bile in urine, ...... 182 
 
 Brewster's mode of illuminating objects, . . . 199 
 
 C. 
 
 Causes of error in observation, . . . . . , 15 
 
 Coal beds, from vegetation, . . . . .14 
 
 Coddington lens, ...... 29 
 
 Compound microscope, . . . . . .31 
 
 defects of the common, . . 33 
 
 improvements in the, . . .33 
 
 mechanical conveniences necessary to the, 35 
 forms of the, . . . .36 
 
 most celebrated makers of the, . 36, 38 
 
 Smith and Beck's, . . .36 
 
 efforts to reduce the price of the, . 38 
 
 Condenser, . . . . . . 41, 53 
 
 for oblique illumination, ... 42 
 
 Condensing (or bull's eye) lens, . . . . 44, 52 
 
 Camera lucida, . . .' . . 37, 47 
 
 Compressorium, ....... 50 
 
 Cook's preserving fluid, . . - r ,- ; . "" ~ ' 56 
 
 Cooper's preserving fluid, ^;. 56 
 
 Cells for mounting, ...... .,.>-. 59 
 
 Cements, ........ 60 
 
 Canada balsam cement, ..... 61 
 
 Charring vegetable matters, . . . . .61 
 
 Carbonate of lime, ...... 67 
 
 Crystallization of salts, ...... 67 
 
 water, ..... 68 
 
 Cuticles, ...... ,..;. ,; . 69 
 
 Cellular tissues, , . 70 
 
INDEX. 205 
 
 PAGE 
 
 Charcoal, . . . . ..,,. 1 . 73 
 
 Circulation in vegetables, ..... 78 
 
 Corals, ...... i ,,^ t , . 86 
 
 Circulation of blood, ..... 96 
 
 Capillaries, their functions, . . . ... 106 
 
 of skin, .... -~ . 100, 109 
 
 of mucous membrane, . . .105,109,167 
 
 Crystalline lens in fish, . . . . . 101 
 
 Ciliary processes of the eye, . . . .' . 101 
 
 movement, . . . . . . 105 
 
 Chromatic aberration, ...... 33 
 
 mode of observing, . . . 110 
 
 Circulatory system of insects, . . . . --;' 126 
 
 Chemical constitution of organized bodies, . . . 130 
 
 Cell-growth in a meliceritous tumor, . . , - -* 137 
 
 Classification of animal tissues, .... 136 
 
 malignant growths, . . . .142 
 
 Carcinoma, ....... 143 
 
 Chemico -gelatinous injection by Dr. Goadby, . . .164 
 
 Cystine in urine, . . . . . . 179 
 
 Colors exhibited by polarized light, . . . .192 
 
 Cleaning the glasses of microscopes, . . . 196 
 
 Cabinet for microscopic objects, . . . . .197 
 
 D. 
 
 9- 
 
 Dissecting microscope of Mr. Slack, ... 27 
 
 Dark wells, . . . . . 38 
 
 Diaphragm, . . . . . . 37, 41, 51, 53 
 
 Deut-ioduret of mercury, . . . . .68 
 
 Dissecting needles, ...... 119 
 
 troughs, . . . . v%, . 120 
 
 Digestive system of insects, ..... 125 
 
 Development of cells, . . . ... 131 
 
 animal tissues, .... 134 
 
 Diabetic urine, ...... 170, 183 
 
 18 
 
206 INDEX. 
 
 E. 
 
 PAGBr 
 
 Erector, . . . . . . " ."*' 44 
 
 Entozoon folliculorum, , . . 91 
 
 Epithelium, ...... '' 1 104 
 
 Examination of morbid structure, . . r * >v . 139 
 
 its importance, . , 141 
 Encephaloid, ....... 146 
 
 Earthy phosphates in urine. . . . 169,171,174 
 
 Eyes of animals, . . . . . . V 101 
 
 F. 
 
 Fossil remains determined by the microscope, . . 14 
 
 Fontana, histological observations of, . . . .17 
 
 Frog plate, , . . . . . . 47 
 
 Fishing tubes, . . . . . . 49, 201 
 
 Fossil wood, ....... 73 
 
 Ferns, . . . . . . . . * 77 
 
 Fibrous and areolar tissue, . . . . . 103 
 
 Forms of nuclei, . . . . . . .133 
 
 Form of fibrous tumor, ..... 141 
 
 G. 
 
 Geology, use of microscope in, . . . . .13 
 
 Goadby's fluids, ...... 57 
 
 manipulating box, . . . <: . 197 
 
 Gum mastich cement, . , J V.S . '-*. c 60 
 
 Glycerine, ...... V 56 
 
 H. 
 
 Histology, created by the microscope, . . ?>** ^ 
 
 II ewson on the blood globules, . . . .-*./ .-, : 17 
 
 Herschell's doublets, . . . . t,^ & 29 
 
 Holland's triplet, . , . . .31 
 
 Huygenian eye-piece, . 35 
 
 Hairs, down, &c., of plants, . . . , .. ,*, .. 73 
 
INDEX. 207 
 
 PAGE 
 
 Hard tissues, ...... 76 
 
 Hair of animals, . . . . . _ .^ 93 
 
 Horn, hoofs, quills, &c., . . . . . ;,..*,. 94 
 
 Human blood, . . . . . . 94 
 
 Hair of Dermestes, . . . . . , .: . ; 114 
 
 Hippuric acid, . . . . . ; "'" - 172 
 
 I. 
 
 Importance of the microscope to zoology, . ' . 14 
 
 Inorganic objects, . . . . . .67 
 
 Illuminating lamp, ... ... 45, 52 
 
 Iron pyrites, . . . . . 68 
 
 Infusoria, classification of, . . . . . 81 
 
 on procuring, . . . . .' ~ . 83 
 
 to observe the structure of, . . *\ 85 
 
 fossil, . . . . . 85 
 
 Insects, antenna) of, . . . . . . 86 
 
 eggs, . . . . 87 
 
 elytra, . . . . . .88 
 
 eyes, . . . . . \ '. t . 88 
 
 feet, . . . . . . 89 
 
 hairs, . . . . . 89 
 
 mouths, &c., . . . . -...- 90 
 
 parasitic, . . $'- :>,# . 90 
 
 trachea, . . . . . . 91 
 
 stings, ovipositors, &c., . . . .91 
 
 internal anatomy of, . . . .123 
 
 Injected papillae of skin, .... 99, 109 
 
 preparations, .... . v -- 106 
 
 Instruments for minute dissection, . . . .118 
 
 Internal anatomy of insects, . 123 
 
 Injecting materials, . >>* . . . 158, 161, 163 
 
 Instrument for diagnosis of tumors, . . r*f ;-" 1^8 
 
 Injection of the lymphatics, . . ' . . 167 
 
 J. 
 Japanner's gold size, ..... 60 
 
208 INDEX. 
 
 PAGE 
 
 Riestein, . . . . . . . -^ - 170 
 
 L. 
 
 Lenses, different forms and effects of, . . 22 
 
 simple mode of making, . . . .28 
 
 imperfections in, ..... 29 
 
 Lewenhoeck, his discoveries, . . . . .16 
 
 Lieberkuhn, his anatomical researches, . . . 17 
 
 concave reflector, so called, . . .46 
 
 Lamp-black cement, ...... 61 
 
 Lichens and fungi, ...... 77 
 
 Loaded corks, . . . . . . 120 
 
 Lepisma saccharina, . . . . . .115 
 
 M. 
 
 Malpighi, microscopic researches of, . . . [15 
 
 Modern observers, . . . . . .19 
 
 Medico-legal inquiries with the microscope, . . 21 
 
 Micrometer eye-piece, ...... 35 
 
 stage, ...... 48 
 
 Magnifying powers, hints respecting, . . . .51 
 
 table of, . . . .; 23 
 
 to obtain the power of a compound micro- 
 scope, . . . . .48 
 
 Mirror, use of the, . . . . . * 52 
 
 Management of the light, . . . . ,52 
 
 Mounting transparent objects, .... 55 
 
 in the dry way, . . 55, 56, 63 
 
 in fluid, . . . 58 
 
 in balsam, . . . 61 
 
 Marine glue, . . .. . . .1 j&^ 60 
 
 Mounting cellular structures, .... y. 62 
 
 opaque objects, ..... 64 
 
 crystals for polarized light, . . . 66, 194 
 
 Mosses, . . . . . , * ; 76 
 
INDEX. 209 
 
 PAGE 
 
 Muscular fibre, . . . . . . .101 
 
 Mucous membrane, . . . . . 104 
 
 Mouse hair, . . . . ... .114 
 
 Morpho Menelaus, . . . . . . 115 
 
 Muscular system of insects, .... *. 128 
 
 Morphology of pathological fluids, . . . . s 149 
 
 Method of injection, by Ruysch, . . . .168 
 
 Rauby, . . ... 163 
 
 Monro, . . . . . 163 
 
 Professor Breschet, . f . 163 
 
 M. Doyere, . . . .163 
 
 Dr. Goddard, . . . 163, 166 
 Mucus in urine, ....... 181 
 
 N. 
 
 Nervous structure, examination of, . . . . 102 
 
 Nerves and capillaries of muscle, ..... 102 
 
 Nervous system of insects, . . . . . 126 
 
 0. 
 
 Organic remains in limestone, . . . . .14 
 
 Optical illusion to be guarded against, . . . 17 
 
 Opaque objects, mounting of, . . . ' 64 
 
 how viewed, .... 53 
 
 Mr. Brooke's mode of viewing, . . 46 
 
 Oolites, 68 
 
 Organic fibres, . . . . . . - . 77 
 
 Oxalate of lime in urine, . . . . 169,176,185 
 
 P. 
 
 Polarizing apparatus, ...... 43 
 
 Preparation of glass slides, ..... 56, 58 
 
 Preserving fluids, . . . . . * 56 
 
 Pollen, / 74 
 
 Pigment cells of skin, . . . . . .100 
 
 of the eye, . . . . . 101 
 
210 INDEX. 
 
 PAGE 
 
 Pontia brassica, . . . . . ...* .116 
 
 Podura plumbea, . . . . >. '..*: H6 
 
 Proximate principles, . . . . . 130 
 
 Primary form of organic matter, . . < $'4 ' 130 
 
 Pus in urine, ..... ..- 170,181 
 
 distinction between it and mucus, . . . 139 
 
 Polarization of light, . . .' . > 188 
 
 Q. 
 
 Qualifications of a microscopist, . . . .;*' 18 
 
 R. 
 
 Religious sentiment, microscope conducive to, . . . 13 
 
 Reflecting microscope superseded, .... 39 
 
 a curious form of, . . . .39 
 
 Rules for microscopic observations, ... 51 
 
 Raphides, . . ; ' ''' . .76 
 
 Retina of the eye, ...... 101 
 
 Respiratory system of insects, ..... 123 
 
 S. 
 
 Simple microscopes, construction of, . ? :-.j, . .,-. 23 
 
 magnifying powers of, . . 23 
 
 mode of mounting, . . > - 23 
 
 form of, for opaque objects, . ..26 
 
 Stanhope lens, . . . . .'*. 29 
 
 Silver cup or Lieberkuhn, . . ..... '. 37,46 
 
 Side reflector, . . . . . 37, 46 
 
 Stage micrometer, ...... 48 
 
 Size of glass for mounting, . ^ . . . 55 
 
 Sealing-wax varnish, . \ . . ' * * . 60 
 
 Sand, ...... . 68 
 
 Sections of granite, &c., . . . . . 68 
 
 coal, . . . , . '. . 68 
 
 wood, . .' . . . ' r . 72 
 
 Siliceous cuticles, .... . - . 73 
 
INDEX. 211 
 
 PAGE 
 
 Starch, . . . - A . . . . . . 74 
 
 Seeds, ; .; ' -.- .. .*., ,' r . > ^ , *;-, 76 
 
 Sponges, . . . ,1. -. "'..$& - * 86 
 
 Shells of mollusca, . . .'& ...,._ .. 91 
 
 Scales of fish, . . . . . , .. * 92 
 
 Skin, ...... v > ,* 99 
 
 Spherical aberration, ..... 33, J10 
 
 Scales of insects, . . . . . . 115 
 
 Shells of infusoria, . . . . . 85,116 
 
 Swammerdam's scissors, . . . . . 118 
 
 mode of dissection, .... 121 
 
 Secondary organic compounds, . . . . 130 
 
 Scrofulous growths, ...... 142 
 
 Syringe for minute injection, . . :<<rcn -- f \ ==. 159 
 
 Stopping false light in microscopes, . . - * . 196 
 
 Substitute for the concave speculum, . . . 200 
 
 T. 
 
 Trough for chara, &c , . . . . . . 37, 50 
 
 Thin cells for delicate tissues, .... 59 
 
 Teeth, . . . . . . 98 
 
 Theory of life and sensation, .... 106 
 
 Test objects, Dr. Goring's discovery of, . . \ 110 
 
 character of, . . . . 114 
 
 Tinea vestianella, ..... "^ 115 
 
 Tables for examination of urinary deposits, . . 185 
 
 of results of Dr. Gruby's observations, . . . 149 
 
 U. 
 
 Utility of the microscope in medicine, . . . 19 
 
 Urinary deposits, . . . . . .169 
 
 Urea, ....... 171 
 
 Uric acid, ...... 169, 171 
 
 Urate of ammonia, . . . . . 180 
 
 soda, ....... 180 
 
212 INDEX. 
 
 V. 
 
 PAGE 
 
 Vegetable physiology, microscope indispensable in, . 14 
 
 Varley's dark chamber, . . . . . . .42 
 
 Vegetable tissues, dissection of, - > .'" . . . 69 
 
 Vascular tissue in plants, . . . . .72 
 
 Vitality and electricity not identical, . . . 108 
 
 Valentin's knife, . ;<' . 'I' . -. . 119 
 
 Vital principle, theories respecting the, . . . 106, 129 
 
 W. 
 
 Withering's Botanical Microscope, . . . .23 
 
 Wilson's Pocket Microscope, .... 24 
 
 Wollaston's doublet, ...... 80 
 
 condenser, ..... 42 
 
 Watch-glasses useful, ...... 49 
 
 White fibrous tissue, . . . . . 103 
 
 Wheel animalculee, mode of obtaining, .... 200 
 
 Y. 
 
 Yellow fibrous tissue, . . . . . 103 
 
 Z. 
 
 Zoophytes, ....... 86 
 
 THE END. 
 
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