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Cornell University Library 
 arV18300 
 
 Histological notes for the use of medica 
 
 3 1924 031 268 208 
 n.anx 
 
Cornell University 
 Library 
 
 The original of tliis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924031268208 
 
HISTOLOGICAL NOTES 
 
 FOR THE USE OF 
 
 MEDICAL STUDENTS. 
 
 BY 
 
 W. HoRSCRAFT Waters, m.a., 
 
 DEMONSTRATOR AND ASSISTANT LECTURER IN PHYSIOLOGY AT THE 
 OWENS COLLEGE, MANCHESTER. 
 
 MANCHESTER : 
 3. E. COENISH, 33 PICCADILLY. 
 
 LONDON : 
 
 SMITH, ELDER, & CO., WATERLOO PLACE. 
 
 ® 
 
TABLE OF CONTENTS. 
 
 PAGE 
 
 I, Moimtmg, Foreign Bodies, etc 1 
 
 n. Blood 7 
 
 III. EpitheUum 10 
 
 IV. Connective Tiaaues 13 
 
 V. Cartilage 17 
 
 VI. Bone 19 
 
 VII. Mnscle 23 
 
 VIII. Nervona Tissues 25 
 
 IS. Bloodvessels 27 
 
 X. Alimentary Canal 29 
 
 XI. Liver 34 
 
 XII. Lnng 35 
 
 XIII. Lymphatic System, Thymus Gland 37 
 
 XIV. Spleen 39 
 
 XV. Duotlesa Glands (Snpra renal Bodiea, Thyroid) 39 
 
 XVI. Kidney, Bkdder 40 
 
 XVII. Skin, Hair 43 
 
 XVEIL Bye 45 
 
 XIX. Organs of Smell, Taste, Touch 47 
 
 XX. Spinal Cord, Brain 48 
 
 XXI. Organs of Keproduction 51 
 
 Hardening Agenta 54 
 
 Staining Eeagenta 55 
 
 Preparation of Tisanes 57 
 
INTEODUGTION. 
 
 In taking the class of Practical Histology at the Owens 
 College Medical School during the Summer Sessions of 1882- 
 1883, it has been my custom to give each student " sheets" 
 containing a short account of the chief points to be observed in 
 the specimens for examination. This plan has been found of 
 great assistance, but the descriptions being of necessity extremely 
 short, it seemed preferable to increase their length, and to 
 obtain this result the following notes have been printed. 
 
 These notes are by no means intended as a full description 
 of the histological structure of the tissues, neither are they 
 given for the instruction of the student in the various methods 
 of section-cutting, injection, etc. ; but simply to aid him in his 
 examination of specimens. 
 
 The specimens were given to the student ready for mounting, 
 since time would not allow him to stain and clear each section 
 for himself; but it is desirable that this course should be 
 followed now and again. 
 
 The various staining, clearing, and mounting reagents are 
 those in general use, but a brief account of those hardening 
 processes, etc., which gave very good specimens, has been included. 
 
VI PRErACE. 
 
 One feels there cannot be too closely impressed upon a student 
 the necessity of introducing method into his examination and 
 description of specimens, and of making sketches to assist 
 himself and his instructor. 
 
 In the description of tissue preparation the same numbers 
 and arrangements have been followed as those used in describing 
 the structure of the specimens. 
 
 I am much indebted to Prof. Gamgee and Prof. Marshall for 
 many kind suggestions, wjbich have assisted me greatly in 
 preparing these notes. 
 
HISTOLOGICAL NOTES. 
 
 I.-MOUNTING, etc. 
 
 The microscope having been placed in a convenient 
 position, and with care that the stand is firm and perfectly 
 steady, the curved mirror is to be adjusted so as to 
 throw a beam of light through the stage-aperture and 
 along the central axis of the tube. Direct sunlight 
 is not to be used for illumination ; that thrown from 
 some bright cloud is strongly recommended. 
 
 The eye-pieces and object-glasses, as well as the 
 mirror, are to be kept perfectly clean and free from dust 
 by means of a soft piece of wash-leather, which should 
 on no account be used for any other purpose. 
 
 Specimens must invariahly be examined first with the 
 low power and then with the high power, using with the 
 former a medium sized diaphragm, and a somewhat 
 smaller one with the latter. Before placing or removing 
 specimens, the objective is always to be withdrawn some 
 distance from the stage by sliding the telescope-tube 
 upwards with a gentle twist. 
 
 When placed, the object may be brought to a focus by 
 gently passing the telescope-tube downwards till the 
 specimen is in view (coarse adjustment), and then by 
 slightly turning the screw at the top of the stand, until 
 a clear and distinct image is obtained {fine adjustment). 
 Care is to be taken that this fine-adjustment screw is 
 not turned too much to the left so as to rise far out 
 from the stand, nor too much to the right and so become 
 fixed. 
 
 It is best to accustom oneself to working with both the 
 left and the right eye, at the same time keeping open the 
 one not directly in use. By this means the eyes become 
 less tired, and with a little practice the whole attention 
 
2 MOUNTING, ETC. 
 
 will be thrown upon the object under examination. It 
 is also of great assistance in making sketches of the 
 preparations. 
 
 I, CeU. 
 
 Yeast. Have a perfectly clean slide and coverslip. Place 
 the former upon some dark surface, dip the end of a 
 clean glass rod into a solution containing yeast, and then 
 touch the centre of the slide, leaving a small quantity 
 of the solution upon it. Holding the edges of the cover- 
 slip between the thumb and forefinger of the left hand, 
 and having a mounting needle in the right one, rest the 
 left edge of the coverslip upon the slide slightly to the 
 left of the yeast drop, and the right edge upon the needle ; 
 then gently lower the latter till the slip touches the 
 yeast and covers it. By this means a specimen may be 
 mounted with less chance of having air-bubbles present. 
 
 At times the body to be mounted is placed upon the 
 coverslip, which is then turned over and lowered upon 
 the slide in a similar manner. 
 
 Be careful in choosing the quantity of solution. If a 
 drop of insufficient size be taken, air-bubbles or air-spaces 
 wiU be present ; while if too large a one be used it will 
 spread over the slide and perhaps the coverslip, when it 
 cannot be examined. The latter is of great importance, 
 and a remount should invariably be made, as any matter 
 upon the upper surface of a coverslip renders the speci- 
 men quite useless. 
 
 The yeast having been satisfactorily " put up," should 
 first be examined with the low power (L.P.). The speci- 
 men appears as a fluid in which are floating cells of vari- 
 able size, some single and others collected in small groups. 
 
 Examine under the high power (H.P.). The ceUs 
 consist of a cell-wall, seen by its double outline, sur- 
 rounding the cells-contents, a mass of granular substance, 
 protoplasm. This protoplasm of the larger cells may 
 have one or more clear spaces, vacuoles, which are not to 
 be mistaken for nuclei, being areas of less dense 
 protoplasm. 
 
 Sketches should now be taken of several cells, both 
 large and small. Placing the sketch book to the right 
 side of the microscope and level with the stage, draw a 
 
MOUNTING, ETC. 3 
 
 faint outline of the cell with the H. pencil, and then 
 carefully finish with the H.B.j making the general 
 protoplasm somewhat darker than the vacuoles, and the 
 granules still darker. 
 
 Sketches of specimens should always be made, and it 
 is best to draw them of the apparent size, or some 
 multiple of the apparent sizej while a note may be 
 placed at the side somewhat after this manner. If under 
 the low power, L.P. ; if under 'the high power, H.P. 
 Under the low power and of the apparent size, L.P. x 1 ; 
 or, if under the low power and three times the apparent 
 size, L.P. X 3, etc. 
 
 II. Application of Reagents. 
 
 In studying the microscopic structure of various bodies 
 it is necessary to add different reagents and staining 
 fluids. Frequently it is best to put up the object and 
 then add the fluid, which may be done : — 
 
 1. By the use of a glass rod and blotting paper ; or 
 
 2. By using the rod and a fine capillary tube. 
 
 As an example study the staining power of a magenta 
 solution upon yeast. 
 
 Mount a specimen of yeast as before and focus under 
 the H.P. Now dip a rod into the magenta solution, 
 place a drop some sbght distance to the left of the 
 specimen, aud, with a needle, lead up a thin stream of 
 the fluid to the coverslip. On the opposite side of the 
 latter place one corner of a small triangular piece of blot- 
 ting paper ; as soon as this touches the yeast solutiou 
 a stream wiU cross the field of the microscope, the 
 magenta flow in, and the cells become stained. The 
 cell-walls will receive no colour, but the protoplasm will 
 stain well, the vacuoles less deeply — a characteristic in 
 which they differ from nuclei. 
 
 In place of the blotting paper a fine capillary tube 
 may be used, with the same results. 
 
 III. Testing. 
 
 By using reagents in the above manner, many 
 substances may be detected under the microscope by 
 characteristic reactions. As examples of this the re- 
 actions of starch and of cellulose may be used, 
 
 B 
 
4 MOUNTING, ETC 
 
 1. Starch. Mount a few granules of starch, by grinding 
 some in cold water and covering a drop upon a slide. 
 Examine under H.P. Pass in a dilute solution of iodine, 
 and the granules turn hhie, a characteristic reaction. 
 
 2. Cellulose. Mount some scrapings from the cut surface 
 of a potato. Examine under the H.P., and run in a 
 little iodine solution ; the starch granules present turn 
 blue, and the walls of the cell-spaces containing them 
 take a yellow tint. If in a similar manner dilute hydric 
 siilphate be now added, this yellow tint will change to a 
 hlue one, indicating cellulose. The same reaction is given 
 by cotton fibres, or the walls of the yeast cells. 
 
 lY. Foreign Bodies, etc. 
 
 In making microscopic preparations, certain bodies 
 from time to time become present which it is necessary 
 to carefully distinguish from the tissues under exami- 
 nation. The more common of these should therefore be 
 placed under the microscope, and sketches made of them, 
 in order that their characteristics may be known. 
 
 1. Brownian movement. This vibratory movement should 
 be carefully distinguished from any vital onej it is 
 shown by some specimens of living matter, but also by 
 non-living matter, and is essentially a physical phe- 
 nomenon. 
 
 (a) Gawhoge. Grind some gamboge in water, and 
 examine a drop under H.P. Various currents may be 
 detected, but also this vibratory, Brownian movement 
 of the small granules. 
 
 (6) Bacteria. Mount a specimen from a watery extract 
 of boiled meat, which has been allowed to stand a few 
 days. Some very fine bacteria will show a similar 
 motion, which lasts after their death, brought about by 
 the addition of iodine or boiling the solution. 
 
 2. Cotton fibres. Mount in water a few fibres of cotton 
 wool, cover and examine under L.P. and H.P. They 
 appear as long, flat threads with a distinct twist, 
 and turn blue on the addition of iodine and hydric 
 sulphate. 
 
 3. Max fibres. Examine in a similar manner some flax 
 fibres; these are long and flat, but unlike cotton ones 
 do not show any twist. 
 
MOUNTING, ETC. 5 
 
 4. Air-hubhles. Shake a solution of gum in a test-tube till 
 a froth appears, then mount a drop of the under fluid, 
 and examine under L.P. and H.P. 
 
 By transmitted light the air-bubbles appear as a bright 
 centre, surrouuded by several dark rings of various 
 depths ; by alteration of the focus these rings wiU 
 change. 
 
 With reflected light (produced by shutting off that 
 thrown from the mirror) a reversion takes place, the 
 centre becoming dark and the periphery light. Sketch. 
 
 5. Fat globules. Mount a small drop of milk and compare 
 the fat globules with (4). Notice their sharp definition 
 and variation of size ; pass in a little sodium hydrate 
 and they immediately run together. 
 
 V. To Prevent Dryiag. 
 
 In examining specimens of tissue for some length of 
 time it is often necessary to prevent evaporation of the 
 mounting medium at the edge of the coverslip, which 
 tends to cause an alteration in their appearance. 
 
 1. With firesli tissues, which are usually examined in serum 
 or normal saline (-75 % solution of common salt) use 
 may be made of oil, paraffin or cocoa butter. 
 
 Oil : best salad oil. After covering carefully to pre- 
 vent any fluid coming beyond the coverslip, a thin film 
 of oil is to be immediately painted round and slightly 
 overlapping the latter. For this purpose a fine camel- 
 hair pencil is used, and is best kept with its holder pier- 
 cing the cork of the oil bottle, that it may be free from 
 dust, etc. 
 
 Paraffin requires to be melted in a capsule before ap- 
 plication. A good preparation may be made of 15 co. of 
 liquid paraffin and 15 grms. : of solid paraffin, kept for 
 about an hour between 40° C. and 50° C. It melts at 
 about 38° C, and is useful in warm-stage experiments 
 for studying the amoeboid movements of white blood 
 corpuscles; the commencement of melting being an indi- 
 cation of the limit of temperature. The same precau- 
 tions must be taken as in the use of oil. 
 
 Cocoa butter. Its use and application are similar to 
 those of paraffin. 
 
 2, Sections, etc., which have been mounted in glycerine or 
 
6 MOUNTING, ETC. 
 
 any media liable to evaporation, require the coverslip to 
 be surrounded and slightly overlapped by some cementing 
 fluid, which will gradually dry and form a firm ring. 
 For this purpose white varnish, brown cement, etc., are 
 good. 
 
 The cement is best applied by centering the coverslip 
 upon a turvAable (that is, arranging the border of the 
 coverslip concentrically with the circles on the brass 
 plate), fixing the slide down with the clips, and while 
 rapidly turning to gently bring a camel-hair pencil hold- 
 ing the cement, down to the edge of the slip. This slip 
 mu&t be carefully centered and the slide firmly clamped, 
 otherwise the rapid rotation of the table will throw ofi' 
 the specimen. To square coverslips the cement may be 
 applied by gentle painting. 
 
 YI. Mounting. 
 
 Preparations of tissues which it is desired to keep, are 
 usually mounted in Glycerine or in solutions of Canada 
 Balsam or Dammar. The solvent of the last two bodies 
 evaporates and leaves a clear hard ring, so that no 
 cement is required as in the case of Glycerine. 
 
 The mounting medium should be quite mixable with 
 that from which the specimen is taken : it being required 
 in some cases to use several fluids to obtain this result. 
 
 Tissues and sections, both stained or unstained, are as 
 a rule kept in spirit, so the following order should be 
 followed in mounting : — 
 
 For Glycerine. For C. Balsam (two ways). 
 
 1. 
 
 Spirit. 
 
 1. 
 
 Spirit. 1. 
 
 Spirit. 
 
 2. 
 
 Water. 
 
 2. 
 
 Absolute Alcohol. 2. 
 
 Absolute Alcohol. 
 
 3. 
 
 Glycerine. 
 
 3. 
 
 4. 
 
 Turpentine and 3. 
 Kreosote (4;1). 4. 
 C. Balsam. 
 
 Oil of Cloves. 
 C. Balsam. 
 
 Glycerine. Pure glycerine may be used or a mixture 
 of equal parts of glycerine and water, which is somewhat 
 preferable. For quick mounting, for specimens which are 
 unstained or hyaline in character, and for those which 
 require teasing, it is better than C. Balsam. 
 
 A section-lifter is required in handling specimens ; and 
 great care should be taken in removing them from spirit 
 
BLOOD. T 
 
 to water : the surface currents causing rapid movements 
 which may lead to the breaking-up of a section. The 
 time during which they should remain in water before 
 removal to glycerine depends upon their size and density, 
 from five to ten minutes being generally sufficient. 
 
 Canada Balsam or Dammar. These are soluble in 
 chloroform, turpentine or benzole, being used for the less 
 transparent and for the stained tissues, rendering speci- 
 mens which are mounted in them very clear. 
 
 The media required in mounting from spirit are to be 
 applied in the order given above ; the specimen being 
 changed from watch-glasses containing them by a section 
 lifter, after removing any excess of each fluid clinging 
 to the specimen by a piece of blotting paper. 
 
 The specimen may remain on the slide, and the media 
 applied by pipettes and removed by blotting paper after 
 their action. 
 
 Five to ten minutes is usually sufficient time for a 
 section to remain in each fluid. 
 
 Take great care that all needles, seekers, section-lifters, 
 etc., are quite clean from one fluid before Ijeing placed in 
 another ; and on no account must the rod or brush of 
 one reagent-bottle be allowed to touch another reagent. 
 
 II.-BLOOD. 
 I. Prog's Blood. 
 
 1. Upon a perfectly clean slide place a very small drop 
 of blood from a frog just kiUed, cover immediately with 
 a clean slip, and quickly surround with oil. Examine 
 first with L.P. and then with H.P.; notice the many red 
 corpuscles and few white ones floating in the plasma. 
 
 jBe(£co?yi«fltej number: very great. Size: . Colour: 
 when seen separately they have a yellow tint, but when 
 collected this deepens to a red one. Shape : flat discs, 
 seen fi:om above they appear elliptical, but seen edge- 
 ways they are very thin, with a gradual swelling in the 
 
BLOOD 
 
 middle portion — ^the position of the mickus ; after a time, 
 particularly in those seen flat, this nucleus becomes more 
 evident and occupies about one third of the area. 
 
 White corpuscles ; number : far less than the red ones. 
 Size : slightly smaller than the red. Shape : if examined 
 quickly it is indefinite, and changes from time to time, 
 amoeboid movements, but on keeping they become round. 
 In appearance they are white with a number of fine 
 grarmdes. Sketch at short intervals a particular cor- 
 puscle, to detect any amoeboid movements. 
 
 The action of various reagents must now be studied. 
 
 2. Water. Mount a fresh specimen, but do not surround 
 with oil as a reagent has to be added. Kun in a little 
 water, by the use of a glass rod and blotting paper as 
 described. The corpuscles swell out to a globular form, 
 and the colouring matter of the red ones, hcemoglobin, 
 difiuses into the surrounding fluid, leaving the remaining 
 portion, stroma, indistinctly seen. 
 
 3. Normal Saline (-75 % solution of sodium chloride). 
 To a fresh specimen add normal saline in a similar 
 manner, no change will take place in either the red or 
 white corpuscles. For this reason the other reagents to 
 be used should be diluted or dissolved in normal saline, 
 and not in water. 
 
 . Acetic Acid 1 %. Add to a fresh specimen as with the 
 above. 
 
 Eed corpuscles : swell ; lose their colour, the outline be- 
 coming indistinct, while an oval shaped nucleus appears 
 at the centre. ' 
 
 White corpuscles : become clear with a few granules ; 
 a nricleus appears, but not, as a rijle, in the centre : at 
 times more than one may be present. 
 
 5. Dilute Alcohol (1 part alcohol, 2 of normal saline). 
 This will cause the red corpuscles to swell, and their 
 nuclei to appear. 
 
 6. Syrup : to be made as a weak solution of sugar. By its 
 action the red corpuscles shrink and assume an irregular, 
 indefinite shape. 
 
 7. Magenta. By the addition of this reagent both cor- 
 puscles stain, but their nuclei do so far more deeply, and 
 become very distinct (page 56). 
 
BLOOD. 3 
 
 8. Boracic Acid 2 %. This acts upon the red corpuscles, 
 causing the colouring matter to separate from the stroma, 
 and collect round the nucleus. 
 
 II. Bird's Blood. 
 
 Kemove the head of a pigeon and aUow the blood to 
 flow into a very small vessel, such as a porcelain crucible. 
 Whip sharply with a few horse-hairs (or small glass-rod) 
 to remove the fibrin, and keep covered with a piece of 
 waxed glass well pressed upon the edges of the crucible. 
 It may be diluted with '75 % salt solution, and will 
 keep a short time for specimens. If sufficient blood be 
 not obtained, the heart may be cut and more collected. 
 
 1. Mount a small drop, as with frog's blood, surround 
 the coverslip with oil, and examine with L.P. and H.P. 
 
 Sed corpuscles ; numerous. Size : much smaller than 
 those of the frog. Shape: elliptical discs, but very 
 pointed at the ends; possess a nucleus. 
 
 White corpuscles, few in number. Shape : very irregu- 
 lar, but tend to become round while mounting, the 
 warm-stage being required to demonstrate their amoeboid 
 shape and movements. They are granular, and their 
 nuclei may be demonstrated by reagents. 
 
 2. Acetic Acid, 1%. "j ^^^^^ j^ ^^^ ^^^^ ^^^ ^ ^^^-^ 
 
 . ?J^^'j. >frog's blood, and similar result's 
 
 4. Magenta. ^^ ^y^^^ 
 
 5. Boracic Acid, 2 /o. / 
 
 III. Hmnan Blood. 
 
 Specimens may be obtained by pricking the top of 
 the finger with a clean needle. 
 1. Mount a very small drop, quickly surround with oil, 
 and examine under L.P. and H.P. 
 
 jRed corpuscles, very numerous. Size : smaller than 
 those of the frog. Colour : yellow or yeUowish-red if 
 seen separately, but a distinct red when grouped .together. 
 Shape : circular biconcave discs ; this concavity may be 
 well detected from the dumb-beU appearance of those 
 seen edgeways, and it is the cause of those seen flat 
 having a dark edge with a bright centre or a bright edge 
 with a dark centre, according to the focus of the micro- 
 
10 EPITHELIUM. 
 
 scope. After a short time they collect in rows with 
 their flat sides together, forming lines or rouleaux. 
 
 White corpmcles, few in number. Size : just slightly 
 larger than the red. Shape : -irregular, but, like those 
 of the bird, they become globular. The cell substance 
 is granular and nucleated. 
 2. Acetic Acid, 1%. Causes a similar effect to that in the 
 frog, but no nucleus appears in the red corpuscle. The 
 white are nucleated. 
 
 i nSiI Saline. } '^^^^^' ^^^ same as in frog and bird. 
 
 5. Drying. Mount a specimen, do not surround with oil, 
 and examine under H.P. The red corpuscles will 
 gradually shrink and become crenate at their edges, from 
 evaporation taking place at the border of the coverslip 
 and a consequent increase in the density of the fluid. 
 
 6. Tannic Acid, 1 %. Examine under H.P. This breaks 
 the physiological connection of the hoemoglobin and 
 stroma of the red corpuscle, and the former ooUeots in a 
 small knob at the border of the latter. 
 
 Demonstrations. 
 
 1. The amoeboid movements of white corpuscles in a 
 specimen of frog's blood placed on a warm stage. 
 
 2. Fibrin filaments in coagulated blood. 
 
 3. Hoemoglobin crystals. 
 
 III.-EPITHELIUm. 
 I. Squamous. 
 
 1. Having previously rinsed the mouth with water, gently 
 scrape the inside of the cheek with the handle of a 
 clean scalpel. Mount the specimen free from air-bubbles, 
 and examine with L.P. and H.P. 
 
EPITHELIUM. 11 
 
 (a) Notice the large squamous epithelial cells, frequently 
 collected in small groups. They are flat, with irregular, 
 curling edgep ; clear, transparent, and possess a nucleus. 
 (Some small granular cells may here and there be 
 seen — ^the salivary corpuscles.) 
 
 (6) Eun in a little 1 % acetic acid to the above, and 
 the nuclei of the epithelial cells will appear more 
 distinctly. 
 
 (c) To a fresh specimen add a small quantity of 
 magenta solution, and the nuclei will stain very well. 
 2. Cast skin of the newt. Stain with logwood and mount 
 in C. Balsam, after passing through the various clearing 
 fluids as previously described (page 6). Examine under 
 L.P. and H.P. 
 
 A layer of polygonal shaped epitJielial cells will be 
 seen, placed edge to edge, and showing at their centres 
 well stained, granular nuclei. Here and there stomata 
 appear. 
 
 II. Colnmnar. 
 
 1. Intestine of rabbit, frog, etc. Gently brush the surface 
 of the small intestine, treated for 24 hours with Eanvier's 
 alcohol and stained in picro-carmine ; carefully break up 
 these scrapings with needles in a little glycerine, and 
 examine with H.P. 
 
 The columnar epithelial cells, single or grouped, have 
 a substance of granular protoplasm with a clear hyaline 
 border at the top, and possess a distinct nucleus. 
 
 In places goblei cells may be seen, the body containing 
 but little protoplasm, being chiefly formed of mucin, 
 which does not stain ; the nucleus is small, and pressed 
 towards the border of the cell. 
 
 III. Ciliated. 
 
 1. Trachea of rat or rabbit. Prepare and mount as de- 
 scribed for the intestine : examine under H.P. 
 
 The cells are columnar and nucleated as above, but in 
 addition, a layer of distinct cilia will be seen on the 
 hyaline border at the top of the cell. 
 
 2. Ciliary movement. In a frog just killed, gently scrape 
 with a clean scalpel the roof of the mouth near the 
 
12 EPITHELIUM. 
 
 eye-ball: mount the scraping in normal saline, cover 
 very gently, and use the H.P. 
 
 Ciliated epithelial cells will be seen, the cilia being in 
 rapid motion, and frequently causing movement of the 
 cells or of any fine granules near them. After a time 
 this becomes less vigorous, and can be more clearly seen; 
 it finally ceases as the ceUs die. 
 
 IV. Pigmented. 
 
 1. Pigmented epithelium of the retina. Carefully remove 
 a piece of this layer from a young eye (prepared) and 
 mount, unstained, in Canada Balsam. If the retina be 
 still attached be sure to mount with the pigment layer 
 uppermost. Use L.P., then H.P. 
 
 The cells are hexagonal in shape, from mutual pressure ; 
 they contain the pigment in fine granules, which are not 
 so dense round the nuclei, these therefore appear in 
 clear spaces. If any cells are observed edgeways, the 
 outer surface is seen straight and clear ; the inner one 
 irregular, and containing the pigment granules. 
 
 V. Stratified. 
 
 1. Bladder. Tease in glycerine the epithelium removed 
 from a dog's bladder treated with Eanvier's alcohol, and 
 stained with picro-carmine. Use L.P. and H.P. 
 
 Notice the various shaped, nucleated cells, passing from 
 the superficial flattened to the lower, more columnar 
 variety. The former show surface markings, due to 
 their pressure on the lower ones. 
 
 2. Cornea. Take a section of the cornea stained in logwood 
 and mount in C. Balsam. 
 
 Under L.P. notice the deeply stained, broad line on 
 the surface, and examine this under HP. This is the 
 outer layer, and consists of a series of stratified epithelial 
 cells, passing from the columnar shaped ones next the 
 general corneal substance, to the superficial squamous 
 variety : each cell has a nucleus. 
 
CONKEOTIVE TISSUBS. 13 
 
 IV.-CONNECTIVE TISSUES. 
 
 Cartilage and Bone will be considered in separate 
 divisions. The three chief factors of connective tissue 
 are (1) yellow, elastic fibres, (2) white fibres, and (3) 
 connective tissue corpuscles ; as far as possible these 
 should be examined separately, and then collectively as 
 forming the ordinary connective or areolar tissue. 
 
 I. Yellow, Elastic Tissue. 
 
 1. Ligamentum nuchse, or lig: subflava. Tease very 
 carefully a piece of the lig: nuchse of an ox.. This 
 teasing should be done by firmly fixing on the slide (with 
 a needle held in the left hand) one end of the piece of 
 tissue, and continually working another needle (held 
 in the right hand) from left to right along the tissue ; 
 by this means the tissue will be broken up into a number 
 of fine filaments. The fibres may be separated by working 
 the needles in a lateral direction to that of the fibres. 
 Now cover with a slip by resting its left edge upon the 
 slide and lowering it with the right needle : by this 
 means a slight current will flow, and float apart the 
 finely divided fibres. Use L.P. and H.P. 
 
 Note the thin ydlow, slightly anastomosing fibres, 
 curling at their free ends. They possess a very distinct 
 and clear outline. 
 
 Run in some 5 % acetic acid, the fibres remain quite 
 unaffected. (N.B. — There may be a small amount of 
 white fibrous tissue mixed with them, which will swell.) 
 
 2. Tease a fresh specimen in glycerine for preservation. 
 
 3. Transverse Section; mount in glycerine, after being 
 stained with picro-carmine. The fibres in section have 
 a polygonal appearance, and are yellow in tint. (The 
 small quantity of red tissue is that fibrous tissue 
 mentioned above.) 
 
 II. White Fibrous Tissue. 
 
 Here again specimens will not consist only of white 
 fibres, a number of connective tissue corpuscles being 
 mixed with them: these two elements constitute the 
 structure of tendon. 
 
14 CONNECTIVE TISSUES. 
 
 1. Tendon, from the tail of a mouse. Kemove the skin 
 from the extreme end of the tail and pull off a vertebra 
 with the thumb-nail and forefinger ; an attached fibre 
 •will be removed. Stretch this across the slide. The 
 middle portion is to be covered with a drop of normal 
 saline, the fibres gently separated at this part with 
 needles, and the coverslip applied. 
 
 The white fibres have a fine, delicate, wavy appearance, 
 running in yaraUd rows. Sketch and compare with (I.). 
 
 Add some 5 % acetic acid, they will gradually sweU, 
 becoming indistinct, while rows of connective tissue cor- 
 puscles appear having a square outline and distinct nuclei. 
 
 2. Tease in glycerine a piece of tendon which has been kept 
 24 hours in picric acid : examine under H.P. The fibres 
 will be seen to have broken up into a number of fine 
 JibrillcB. 
 
 3. Longitudinal section of tendon (tendo Achillis of dog) : 
 stain in logwood and mount in C. Balsam. 
 
 The corpuscles will be seen arranged in parallel rows 
 and nucleated. At parts deeper tinted, longitudinal 
 markings appear on the corpuscles, from seeing through 
 a thicker piece of the cell substance, as will be explained 
 from the next section. The fibres do not stain well. 
 
 4. Transverse section of tendon. (Tendo Achillis of dog, 
 or tail of young mouse; in latter case the bone, 
 blood vessels, etc., must be disregarded.) Logwood; 
 C. Balsam. 
 
 L.P. The fibres appear transversely cut and bound 
 together in fasciculi by small bundles of areolar tissue. 
 
 H.P. The fascicuh contain deeply stained, irregular 
 bodies throwing off numerous thin branches : these are 
 the corpuscles in transverse section, their branches 
 surrounding the fibres of the tissue. 
 
 III. Connective Tissue Corpuscles. 
 
 1. Cornea of frog. Mount flat in glycerine a gold pre- 
 paration of the frog's cornea. Disregard the fine nerve 
 fibres stretching and branching in various directions, 
 but study carefully the well-stained corpuscles. The 
 latter have large granular bodies and throw off numerous 
 branches, those of neighbouring corpuscles appearing to 
 be connected. 
 
CONNBCTIVB TISSUES. l5 
 
 2. Tadpole's tail. ^TE«^ in glycerine a piece from the 
 thinner portion. A oetter method is to out oflf a piece 
 of the taU, divide by scissors along the muscular median 
 line, and split open one of these halves by needles : when 
 split the two layers of epithelium should lie down on the 
 glass slide and the connective tissue substance of the tail 
 can be readily examined, after covering with a slip. 
 This should be done in glycerine. 
 
 Between the developing blood vessels, numerous 
 connective tissue corpuscles will be seen : they are well 
 branched, granular and micleated, many possessing a good 
 amount of pigment. 
 
 IV. Areolar Tissue (Connective Tissue). 
 
 1. Sub-cutaneous tissue. Here all the factors will be well 
 distinguished. From under the skin of a freshly-killed 
 animal (rat) snip off a piece of the light fibrous tissue, 
 by lifting it up with a pair of forceps and cutting a short 
 distance below with a pair of scissors. Quickly place on 
 a clean slide and spread out with needles, very gently 
 breathing on it novsr and again to keep it moist. Mount 
 directly by placing a drop of normal saline upon a cover- 
 slip and covering. 
 
 Examine under H.P. with a small diaphragm. Nu- 
 merous bands of white fibres will be seen running in 
 various directions and possessing their characteristic wavy 
 appearance. Not so distinctly, the yellow elastic fibres 
 appear : they are less in number, very fine, and connected 
 at times by branches. With care, connective tissue cor- 
 puscles may also be seen, showing their irregular branches. 
 
 Add a small quantity of 5 % acetic acid, and the white 
 fibres swell, gradually disappearing, whUe the elastic 
 fibres and corpuscles stand out more distinctly. At 
 points bodies resembling white blood corpuscles may be 
 seen, leucocytes. 
 
 V. Adipose or Patty Tissue. 
 
 This modified form of connective tissue is best exa- 
 mined in specimens containing comparatively few fat 
 cells, as parts of the mesentery, omentum, etc. 
 1. Omentum, Carefully spread out in normal saline, a 
 piece of omentum from a freshly killed rat ; cover, and 
 
16 CONNECTIVE TISStJBS. 
 
 selecting a part wMch does not contain much fat, exa- 
 mine under L.P. and H.P. (N.B. — If a rat be used care 
 must be taken not to mistake tbe pancreas, which 
 spreads over the mesentery, for fat.) 
 
 With L.P. the fat cells will be distinguished as large, 
 bright, highly refracting hoaies mixed with the tissue 
 fibres. 
 
 Under H.P. one can distinguish the fibres and see the 
 individual cells with a distinct and oval outline. In 
 some a small amount of granular protoplasm may be 
 seen between the oeU-wall and the outline of the fat 
 globule or globules. 
 2. Mount in 0. Balsam another piece of omentum which 
 has been in alcohol for 24 hours, stained with logwood 
 and passed through absolute alcohol, then turpentine 
 and kreosote (page 6). The fat will have been dis- 
 solved from the ceUs, which under H.P. show the cell- 
 wall and niideus ; the latter, during the formation of the 
 fat, may have been pressed towards the wall, which also 
 may have become irregular in outline during preparation. 
 The cells wiU be seen to be embedded in connective 
 tissue. 
 
 VI. Adenoid, Lymphoid or Retiform Tissue. 
 
 1. Lymphatic Gland. Gently shake in water and mount 
 in glycerine a very thin section of fresh lymphatic gland, 
 cut with the freezing microtome. 
 
 H.P. Disregarding the coat and trabeculse of fibrous 
 tissue, notice the fine reticulum of branching connective 
 tissue corpuscles. Their small bodies throw off many 
 &\a,meQ.tons processes, which joining those of neighbouring' 
 cells form a reticulum. The meshes are seen to contain 
 leucocytes — and the shaking in water is adopted to 
 remove as many as possible. 
 
 Demonstrations. 
 
 1. Silver preparation of tendon, to demonstrate the cor- 
 puscles by "negative images." 
 
 2. Eeduction of osmic acid by fatty bodies and its use for 
 demonstrating fat cells. 
 
 3. Development of fat cells. 
 
OAEWI/AGE. 17 
 
 V.-CARTILAGE. 
 
 Cartilage consists essentially of cells embedded in a 
 matrix or ground substance, and its chief forms arise 
 from variations in the structure of the latter. The 
 hyaline cartilages have a transparent or slightly granular 
 matrix, aud the different kinds may be distinguished by 
 the arrangement of the cells. In yeUow elastic cartilage 
 the matrix is permeated by fine fibrillse of elastic tissue ; 
 and white fihro-cartilage has a matrix showing white 
 fibrous tissue. 
 
 I. Hyaline Cartilage. 
 
 1. Shoulder-girdle of the newt, or the transparent portion 
 of the frog's sternum, are good examples of simple 
 hyaline cartilage. Snip ofi' a small piece from a freshly 
 killed animal, scrape gently, to remove any adhering 
 tissue, and moimt in normal saline. 
 
 Under H.P. a hyaline or very finely granular matrix 
 will appear, studded with oval cells or corpuscles filling 
 the cell spaces and consisting of granular protoplasm with 
 one or two nuclei. In some parts, neighbouring cells 
 will have their proximal sides flattened. 
 
 Eun in a little acetic acid ; the cells wiU shrink away 
 from the cell spaces, their protoplasm become granular 
 and their nuclei appear very distinctly. 
 
 Kemove the specimen, wash it well in normal saline 
 and place for a few minutes in logwood (or hsematoxylin), 
 wash again and mount in glycerine. The nuclei become 
 very distinctly stained and the matrix slightly so. 
 
 2, Articular cartilage. Take a section, vertical to the 
 articular surface and including a small piece of the 
 (softened) bone : stain with eosin and mount in glycerine. 
 
 L.P. Note the smooth free surface of the cartilage, 
 and also its line of junction with the bone : the cells 
 are distributed throughout the matrix, but get closer 
 together towards the surface. 
 
 H.P. The matrix is clear and hyaline; the cells in 
 the deeper portion, near the bone, are round, granular, 
 nudeafed and frequently grouped from ceU division, but 
 on approaching the free surface they become flattened 
 
18 CABTILAGB. 
 
 in a direction parallel to the articular surface and 
 the amount of matrix between them decreases. The 
 cell substance is granular and the nuclei are distinct. 
 
 3. Head of frog's femur. Section vertical to the surface 
 and treated as above (2). 
 
 In this specimen the arrangement and flattening of the 
 cells, as the surface is reached, can be clearly seen, and 
 the process of cell division is most distinct : the two or 
 more daughter cells from division of the mother cell. 
 
 4. Costal cartilage; logwood, glycerine. H.P. The chief 
 points to notice are, the very distinct grouping of the 
 cells and the presence of fat-globules in their protoplasm. 
 At the surface of the cartilage the cells become flattened. 
 
 5. Parenchymatous cartilage. Carefully remove the skin 
 from both sides of the ear of a mouse ; clean from 
 adhering tissue and mount in glycerine. 
 
 L.P. The specimen appears cellular from the small 
 amount of matrix : at places holes are seen in the carti- 
 lage. 
 
 H.P. Note the very small amount of matrix and the 
 consequent approximation of the cells, giving rise to the 
 name, parenchymatcms. The cells are similar to those of 
 former specimens. 
 
 II. Yellow Elastic Cartilage. 
 
 1. Epiglottis (or pig's ear). Stain a section with picro- 
 carmine and mount in glycerine. 
 
 L.P. shows a matrix (yellow) containing many cells 
 (red). 
 
 H.P. The matrix appears clear just round the cell- 
 spaces but granular in other regions j if carefully studied 
 this granular appearance is seen due to fine fibrillations 
 of yellow elastic tissue. 
 
 2. Arytenoid cartilage (sheep) ; take a section through the 
 point of attachment of the vocal cords, and parallel to 
 their direction ; stain with picro-carmine and mount in 
 glycerine. 
 
 L.P. The cartilage at one portion of the section ap- 
 pears hyaline, at the other end fibrous. 
 
 H.P. Examine the section at the junction of the 
 above parts and fine elastic fhres will be very distinctly 
 seen, running from the denser elastic cartilage to the 
 
BONE. 19 
 
 hyaline matrix of the other portion. Trace these fibres 
 and study their denser packing on approaching the cords. 
 The cartilage cells and rvuclei stain with the carmine. 
 
 III. White-Pibro Cartilage. 
 
 1. Section of ligameutum teres and head of femur. This 
 is to be made parallel to the direction of the fibres of 
 the ligament, stained with carmine and mounted in gly- 
 cerine. 
 
 L.P. White fibrous tissue gradually passing into the 
 cartilage can be claarly seen : select that portion showing 
 the transition and examine under H.P. 
 
 H.P. At the above point the matrix is seen to con- 
 sist of a number of parallel fibres similar to those of (II. 
 1) in connective tissue. The cells however are distinctly 
 cartilage cells, round, clear and nucleated, but arranged in 
 rows parallel to the direction of the fibres ; they stain 
 well in carmine. Follow the specimen towards the arti- 
 cular surface at the head of the bone, the cells become 
 irregularly arranged and an articular cartilage is foimd ; 
 in the opposite direction the cells take the appearance of 
 the connective tissue corpuscles found in tendon (II. 1 
 of connective tissue). 
 
 2. Interarticular cartilage (intervertebral). Cut a ver- 
 tical section through two neighbouring vertebrae, stain 
 with carmine and mount in glycerine. 
 
 Examine under H.P. ; the cartilages on the surface of 
 the neighbouring vertebrae will appear and the fibrous 
 tissue passing between them. Here the fibro-cartilage, 
 close to the bone and with the appearances above 
 described, may be seen. 
 
 VI.-BONE. 
 
 Specimens of bone when examined may be seen in a 
 close, dense form known as compact bone ; or of a less 
 dense form, consisting of a number of slender bars or 
 
20 BONE. 
 
 spicula joining here and there to form a network, and 
 tiien spoken of as spongy or cancellated bone. These 
 pass gradually from one form to another, and in minute 
 structure are seen to consist of the same elements. 
 
 To detect the histological structure, specimens of hard 
 and of softened bone must be examined. 
 
 I. Hard Bone. 
 
 1. Transverse section of long (compact) bone. Place 
 under L.P., and note the large medullary canal sur- 
 rounded by a ring of osseous tissue. The latter will show a 
 number of round, dark spaces distributed throughout 
 its substance ; they are the transverse sections of Haver- 
 sian canals, tubules which in the living condition carry 
 blood-vessels ; they will vary in shape according to the 
 relation of the plane of the section to the direction of 
 the canals. A number of fine, concentric lines indicate 
 the presence of the lamellae, and with these are seen 
 very small, dark, irregular spaces, the lacuncB. In this 
 specimen the lamellsB are seen to be arranged in distinct 
 systems : — 
 
 1. Circumferential or Peripheral system : placed at the 
 outer surface of the bone, and in which the lamellse run 
 parallel to the outer surface. 
 
 2. Haversian systems : in which a number of con- 
 centric lamellse are arranged round the various Haversian 
 canals, the latter being placed in the centre. 
 
 '3. Perimedullary system : where the lamellae run 
 parallel to the inner (medullary) surface of the bone. 
 These are not always present, there being irregular 
 Haversian spaces around which the lamellse are placed. 
 
 4. Intersystemic : where rows of lamellse occupy irre- 
 gular spaces between the Haversian systems. 
 
 Examine an Haversian system under the H.P. Ar- 
 ranged with the lamellse are the dark (air-filled) lacunoe, 
 generally elongated in the direction of the former, very 
 irregular in outline and giving off in various directions 
 fine branches, canaliculi. On carefully tracing the canali- 
 ouli, those of neighbouring laounse will be seen to anas- 
 tomose, while some from the row of lacunae placed next 
 to an Haversian canal open into that cavity. Careful 
 sketches must now be made under both L.P. and H.P. 
 
BONE 21 
 
 2. Longitudinal section of long (compact) Lone. This is 
 to be examined in a similar manner to the above. The 
 chief points to notice are : the direction of the lamellae, 
 generally parallel to the long axis of the bone ; and the 
 Haversian canals. The latter run along the bone some- 
 what parallel to each other, and are joined by transverse 
 branches. 
 
 3. Section of frontal bone. Examine as above. L.P. 
 shows two peripheral plates of com/pact, enclosing a mass 
 of cancellated bone. 
 
 The H.P. wiU show the ultimate structure of the 
 different parts to be similar to that of sections 2 and 3. 
 
 II. Softened Bone. 
 1. Transverse section of long bone. Stain with picro-carmine, 
 and mount in glycerine. 
 
 Examine under L.P. and note the various parts as 
 seen in the similar section of hard bone; from the 
 method of preparation the lacunae, oanaliouli, and 
 Haversian canals wiU not appear as dark spaces but as 
 red-coloured parts in a less deeply tinted ground (bone 
 substance). 
 
 H.P. Carefully study a lacuna, which is occupied by 
 a stained hone corpuscle sending ftrajicAcs into thecanaliculi, 
 and containing a distinctly stained nucleus. The 
 Haversian canals are occupied by some fine connective 
 tissue surrounding the section of a hlood vessel (in parts 
 of the specimen this section may have fallen out during 
 the course of preparation). 
 
 2. Longitudinal section of long bone; picro-carmine, 
 glycerine. 
 
 Under L.P. and H.P. compare this section with the 
 above, and examine the various tissues as described. 
 
 3. Frontal bone ; carmine, and mount in C. Balsam. The 
 bone substance is similar to the above. The spaces 
 of the spongy bone are filled with marrow, and contain 
 fat cells. 
 
 III. Sharpey's (perforating) fibres. 
 
 1. Carefully remove (under dilute glycerine in a capsule) 
 a few lamellae from the piece of a softened frontal bone, 
 by holding down the lower part of an edge with forceps. 
 
22 BONE. 
 
 and tearing off the upper part with another pair ; mount 
 in glycerine with the lower surface uppermost ; or 
 2, Tease off the outer lamellse from a coarse vertical section 
 of the same. At various parts of the specimens fine, 
 elongated Sharpey^s fibres will be seen, gradually passing 
 to a fine point. In the last method of preparation the 
 elongated, conical spaces occupied by these fibres may 
 appear. 
 
 IV. Periosteum. 
 
 1. Adult bone. Place specimens IT. 1 and 2 under the 
 H.P. The outer surface will appear more deeply stained, 
 the periosteum • this consists of connective tissue which 
 next to the bone substance contains a greater proportion 
 of yellow, elastic fibres. 
 
 2. Young bone : carmine, glycerine. Under H.P. the 
 periosteum has a similar appearance to that above, but 
 between the yellow elastic fibres and the bone substance 
 a nvunber of well stained granular corpuscles are seen, 
 the osteoblasts. 
 
 v. Marrow. 
 
 Described as of two kinds, viz. yellow marrow and red 
 marrow. 
 
 1. Yellow marrow. Remove a small piece from the inside 
 of a fresh long bone and mount in a little normal saline. 
 Under L.P. and H.P. it is seen to consist chiefly of con- 
 nective tissue and fat cells. 
 
 2. Red marrow. Break across the long bone of a guinea- 
 pig, and mount a small piece of the marrow in normal 
 saline, surrounding with oil Fat cells are few. Some 
 red-coloured cells may be seen and also large indefinite- 
 shaped giant cells (myeloplaxes) with large or several 
 nuclei ; while round marrow cells with clear protoplasm 
 and nuclei appear. 
 
MUSOIiE. 23 
 
 VII.-MUSCLE. 
 
 I. TJnstriated (Involuntary) Muscle. 
 
 1. Carefully and finely tease in glycerine a small piece of 
 muscular tissue from the intestinal walls. This should 
 have been placed in water for a short time after removal 
 from the spirit (page 59). 
 
 Under H.P. and with a small diaphragm. Notice the 
 long, spindle-shaped cells of unstriated muscle fibres, each 
 with a distinct, elongated nwileus placed at the centre 
 and finely granular in appearance. Examine also groups 
 of these cells and their arrangement. 
 
 2. Frog's hladder. Stain with logwood or carmine, and 
 mount in C. Balsam, the specimen being carefully spread 
 out to prevent creases. 
 
 Examine with L.P. and H.P. Disregard the round 
 nuclei of the connective tissue corpuscles and of the 
 endothelial cells of the blood vessels. Note the elongated, 
 unstriated muscle fihres, collected in fxasMhundles, running 
 in various directions, and containing the well stained 
 
 3. Transverse section of the muscular coats of the small 
 intestine, to show the fibres in section ; stain with log- 
 wood, mount in C. Balsam. 
 
 With H.P. note the two layers, one with the fibres out 
 longitudinally, the other transversely. The former have 
 an appearance already described ; the latter appear round 
 or slightly angular, some containing a deeply stained spot 
 where the razor has passed through the micleus. This 
 will not occur in every fibre, and the section should be 
 compared with the transverse section of a meduUated 
 nerve fibre (page 26) to note the distinguishing points. 
 Between the fibres a certain amount of fine tissue may 
 be seen. 
 
 II. Striated (Voluntary) Muscle, 
 
 1. Fresh muscle. Remove a small piece from the thigh of 
 a freshly killed frog and tease carefully, but well, in nor- 
 mal saline ; cover and examine under L.P. There are 
 numerous muscle-fibres embedded in fine connective tis- 
 sue (endomysium). 
 
24 MUSOLE. 
 
 Under H.P. carefully study an individual j^6re; it has 
 a striated appearance from the presence of alternate light 
 and dark bauds in a transverse direction. Here and 
 there the muscle substance will have shrunk away from 
 its sheath or sarcolemma, which shows as a fine distinct 
 line parallel to the direction of the fibre ; or in places 
 the muscle substance will have been broken across and 
 this sarcolemma will appear as two distinct lines joining 
 the outer edges of the separated pieces. 
 
 Sketch the above, and then run in a little acetic acid; 
 in a short time the mass becomes granular and micld 
 appear distributed throughout its substance. 
 
 2. Striations. Tease in glycerine a piece of crab's muscle 
 or a piece of water-beetle's muscle, kept a few days 
 in spirit. 
 
 Under H.P. the striations from the alternate light 
 and dark lines appear very clearly. 
 
 3. Muscle flbrillsB. Tease in glycerine a piece of muscle 
 hardened in -5 % chromic acid ; or a piece of boiled meat. 
 The fibres will be seen to have split longitudinally, into 
 a number of very fine flbrilloe, which still show the 
 striations. 
 
 4. Muscle discs. Tease and examine in a similar manner 
 a small piece treated with 2 % hydrochloric acid. Here 
 the fibres wiU be seen to have broken up transversely, 
 forming the muscle discs. 
 
 5. Transverse section. Stain with logwood and mount in C. ' 
 Balsam a section of dog's muscle. 
 
 L.P. shows the fibres in section, with connective tissue 
 between them (endomysium). The fibres are collected 
 in bundles iorxning fasciadi. 
 
 H.P. The fibres appear as definite elements, showing 
 a clear outline, the sarcolemma, inside and close to which 
 lie the well stained nnclei. Within the areolar tissue 
 between the fibres, blood vessels may be seen in section. 
 
 III. Cardiac Muscle. 
 
 1, Tease in glycerine a piece of cardiac muscle, previously 
 stained with picro-carmine. Under the L.P. pick out a 
 few well separated fibres and examine under H.P. 
 
 Here and there the cells may be seen to give ofi" a 
 small branch; they are but slightly greater in length 
 
NERVOUS TISSUES. 25 
 
 than in breadth ; their striations are much less distinct 
 and regular than in ordinary striated muscle ; they possess 
 no sarcolem/ma and the nuclei are oval, centrally placed 
 with but one (or at most two) to each cell. The cells 
 are joined end to end and this junction may be clearly 
 distinguished. 
 
 VIII.-NERVOUS TISSUES. 
 
 I. SEednllated Nerve Fibres- 
 
 1. Fresh nerve. Eemove a small piece from the sciatic (or 
 other large nerve) of a freshly-kiUed frog ; spread out 
 and quickly tease upon a dry slide, by holding one end 
 with a needle and working from this end in the direction 
 of the tibres with another needle ; add a drop of normal 
 saline, cover, and examine with L.P. 
 
 The nerve is seen to be formed of Jihres bound to- 
 gether by fine areolar tissue. 
 
 H.P. 'Esioh. fibre is distinctly marked, and possesses a 
 highly refracting medullary sheath (white substance of 
 Schwann) which escapes at the end of a cut fibre in 
 fatty globules. This sheath is covered on the outside 
 by a fine membrane, the primitive sheath (sheath of 
 Schwann) which with care may be distinguished at dif- 
 ferent points as a fine line. 
 
 2. Spread out a fresh piece of nerve in the same manner, 
 but add a drop or two of chloroform (instead of normal 
 saline) and cover, being careful during the examination 
 that all the chloroform does not evaporate. This dis- 
 solves the fatty substance of the medullary sheath. 
 
 H.P. The primitive sheath may be distinctly seen, 
 and running along the middle of the fibre appears a 
 granular line, the axis-cylinder. 
 
 3. Tease in glycerine some frog's nerve, slightly teased and 
 allowed to remain in 1 % osmic acid for about two hours. 
 Select under L.P. a long and distinct fibre. 
 
26 NERVOUS TISSUES. 
 
 H.P. Study the medullary sheath, which is stained by 
 the osmio acid and appears broken at short intervals ; 
 ■within this lies the lighter axis cylinder. Trace along 
 the fibre and at certain points a constriction appears, 
 the medullary sheath stops while the axis cylinder passes, 
 a node of Ranvier. About midway between two nodes 
 of Ranvier, and lying just beneath the primitive sheath, 
 the unstained nucleus (surrounded by a little granular 
 protoplasm) may be seen projecting into the dark 
 medullary sheath. 
 4. Transverse section of a nerve (large). Stain with log- 
 wood, mount in C. Balsam. During the mounting the 
 fatty substance of the medullary sheaths will have been 
 dissolved. 
 
 L.P. The section is seen to be built up of separate 
 nerves, each bounded by a fine line, a section of the 
 perineurium, and held together by connective tissue, 
 epineurium ; the nerves consisting of nerve fibres with 
 endoneurium between them. 
 
 H.P. The section of each nerve fibre shows a fine 
 circular line, primitive sheath, enclosing a space occupied 
 by the medullary sheath, in which lies a deeply-stained 
 spot, the divided axis-cyUnder. Compare with the trans- 
 verse section of unstriated muscle fibres (page 23). 
 
 II. Non-Mednllated Nerve Fibres. 
 
 1. Eemove the nerve from the fresh spleen of an ox, care- 
 fully tease in glycerine, and examine under H.P. Note 
 few medullated and many non-medullated nerve fibres ; 
 the latter are pale and granular, each showing numerous 
 oval nuclei, a primitive sheath and an axis cylinder. 
 
 2. Cornea. Examine under H.P. the gold preparation of the 
 frog's cornea (page 14). The nerve fibres will be seen, 
 non-medullated and dividing into many branches, the 
 finest of which show numerous slight thickenings along 
 their length — varicose nerve fibres. The finest branches 
 have no primitive sheath. 
 
 III. Nerve Cells. 
 
 1. Spinal cord, Tease well in glycerine a piece from the 
 anterior cornu of the lumbar region (ox) previously 
 stained with carmine. 
 
BLOOD VESSELS. 27 
 
 L.P. Note the fine mass of oonijective tissue, nerve 
 fibres, and large, branching, multipolar nerve cells. 
 
 H.P. Examine a nerve cell : it consists of a granular 
 cell body throwing off numerous dividing branches, and a 
 large distinct nucleus in which lies a deeper stained 
 nucleolus. Sketch under both L.P. and H.P. 
 2. Mount in C. Balsam, a section of the ganglion on the 
 posterior root of a spinal nerve, stained in carmine. 
 
 L.P. Disregard the nerve fibres and areolar tissue, 
 but study the collection of ganglionic cells. 
 
 H.P. Each cell possesses a nucleus and nucleolus, and 
 is enclosed in a nucleated capsule ; some may be seen to 
 give off a branch. 
 
 Demonstrations. 
 
 1 . Silver preparation to show the nodes of Ranvier. 
 
 2. Transverse section of medullated nerve fibre treated 
 with osmio acid, to show the cylindrical nature of the 
 medullary sheath. 
 
 3. Unipolar nerve cells of Bidder's ganglion in the 
 frog's heart. 
 
 IX.-BLOOD VESSELS. 
 I. Arteries. 
 
 1. Medium sized artery. Transverse section ; logwood, C. 
 Balsam, 
 
 L.P. Note the three coats : — 
 
 1. Inner coat, appears clear and narrow. 
 
 2. Middle coat, broader and well stained. 
 
 3. Outer coat, not well stained and irregular in limi- 
 tation. 
 
 H.P. The inner coat may show at its inner edge a 
 few nuclei of the endothelial cells which line it ; beneath 
 these lies a clear line of regular thickness, the layer of 
 yellow elastic fibres. 
 
 Of the middle coat, the circularly arranged, unstriated 
 muscular fibres with their distinct nuclei may be seen, 
 and between these a certain amount of connective tissue 
 appears in wavy lines. 
 
28 BLOOD VESSELS. 
 
 The outer coat is less stained, and it is built of fibres 
 of connective tissue, between which the connective tissue 
 corpuscles appear by their nuclei, which stain well. 
 
 2. Large artery. Transverse section, stained with picro- 
 carmine, mount in C. Balsam. 
 
 L.P. Compared with the mediimi sized artery it is 
 seen to have the same number of coats ; the middle one 
 is, however, comparatively less thick, the outer one 
 thicker. 
 
 H.P. Distinguish the various elements as in 1, and 
 note the greater amount of connective tissue compared 
 with the muscle fibres in the middle coat. 
 
 3. Arterioles. Stain with carmine a specimen of pia 
 mater removed from a young animal and hardened ; 
 mount in C. Balsam. 
 
 H.P. Disregard the areolar tissue and study the 
 small arteries ; note the elongated nuclei of their mus- 
 cular fibres axra,nged transversely; in the smallest only 
 one layer is seen. By careful focusing the more circular 
 nuclei of the endothelial cells lining the arteries, may be 
 distinguished. 
 
 4. EEdothelial cells lining the arteries. Carefully spread 
 and mount in C. Balsam a specimen of frog's bladder in 
 which the blood-vessels have been injected with silver 
 nitrate (page 61). 
 
 H. P. Note the smallest vessels (capillaries) and larger 
 ones (arteries and veins). Examine the endothelial cells 
 of the arteries, indicated by the black outlines ; they are 
 more elongated compared with those of the veins. 
 The transverse lines seen crossing the vessels are indica- 
 tions of the muscular fibres (3). 
 
 5. Fenestrated membrane or layer of elastic fibres, under- 
 lying the sub-endothelial layer. Carefully tear ofi' the 
 inner coat of an artery from a large animal, and after 
 cleaning, tease in glycerine. 
 
 H.P. It consists of a layer of yellow elastic fibres, 
 which at times form a membrane with numerous holes 
 (fenestrated). 
 
 II. Capillaries. 
 
 1. Frog's bladder. Examine under H.P. the silver pre- 
 paration I. 4. Choose a small artery, and gradually 
 
ALIMENTARY CANAL. 29 
 
 trace its finer and finer branches till they open into 
 capillaries. These are distinguished by not showing 
 transverse lines to indicate muscle fibres, having but a 
 single layer of endothelial cells as constituting their whole 
 structure. At points the intercellular substance (which 
 is the dark part reducing the silver nitrate) appears as a 
 dark patch. Trace the capillaries in the same direction 
 and they will be seen to collect and open into veins. 
 2. Pia mater. Examine under H.P. specimen I. 3, and 
 trace, as before, an artery till it opens into capillaries, 
 indicated by the absence of the transverse nuclei of 
 muscle fibres ; these fine tubes show very distinctly the 
 stained nuclei of their endothelial cells. 
 
 III. Veins. 
 
 1. Transverse section of medium sized vein; stain in 
 logwood, mount in C. Balsam. 
 
 L.P. The thickness of the walls is much less than 
 that of an artery of the same calibre ; but the internal, 
 middle, and outer coats still appear. 
 
 H.P. In the internal coat the muilei of the endothelial 
 cells and the layer of elastic tissue may be seen. The 
 middle coat shows muscular fibres with their stained 
 nuclei, but they are mixed with a great deal of connective 
 tisme ; and the line of demarcation between the middle 
 coat and the outer one is far less distinct than in the 
 artery. 
 
 2. Endothelial cells: examine the silver preparation of 
 frog's bladder, I. 4, under H.P. The endothelial cells are 
 very distinct, but are broader than those of the arteries. 
 
 X.-ALIMENTAET CANAL. 
 I.— Tongue. 
 
 1. Tongue of cat : vertical section through the upper por- 
 tion ; logwood, C. Balsam. 
 
 L.P. An epithelial covering surrounding a mass of 
 striated muscle fibres embedded in connective tissue. At 
 points the surface of the epithelium forms a number of 
 papillce. 
 
30 
 
 ALIMENTAHT CANAL. 
 
 H. P. Epithelium is seen to be stratified, the lower cells 
 being somewhat columnar and gradually passing to flat 
 ones at the surface ; nuclei show welL Separated from 
 the epithelium by areolar tissue, and surrounded by the 
 same, are bundles of striated muscles which are cut in 
 various directions and show distinct nuclei. At points 
 mucous glands may be seen. 
 
 H.-Tooth. 
 
 1. Vertical section of human tooth. Under L.P. it is seen 
 to consist of a pidp cavity smrounded by dentine ; the 
 latter is marked with wavy, radial lines, and is covered 
 at its upper portion by a sheet of enamel, and by the 
 crusta petrosa at the lower part : each narrowing gradu- 
 ally to their line of junction. 
 
 H.P. The Enamel consists of (polyhedral) prisms ar- 
 ranged perpendicularly to the surface of the dentine : 
 concentric lines may be seen passing across them in a 
 direction somewhat parallel to the surface. 
 
 The radial lines of the Dentine are seen to be fine tubules 
 opening from the pulp cavity and passing through the 
 matrix of the dentine towards the crusta petrosa or 
 the enamel ; sometimes dividing dichotomovMy, gradually 
 growing finer during their passage, which is in wavy lines, 
 the latter being small secondary waves placed upon larger 
 primary ones. At times transverse incremental lines 
 appear, which are formed of interglobular spaces having 
 outlines of imperfect circiilar curves. 
 
 The Crusta Petrosa will show lacuncB and canaliculi as 
 in bone, but the former are much more irregular and no 
 Haversian canals are seen. 
 
 2. Transverse sections of various parts are to be compared 
 with the above. 
 
 III. Salivary Glands. 
 
 1. Mncous gland: submaxillary gland of dog; logwood, 
 C. Balsam. 
 
 L.P. Gland is seen to consist of a number of dv,cis 
 and alveoli embedded in fine connective tissue, which 
 contains many blood-vessels. 
 
 Select a thin portion and examine under H.P. Ducts : 
 consist of a single layer of columnm" epithelium cells, 
 
ALIMENTARY CANAL. 3l 
 
 each having a centrally placed nucleus and protoplasm 
 granular towards the aperture of the duct but faintly 
 striated with radial lines at the peripheral portion. 
 The alveoli are built of two kinds of cells : chiefly of 
 cells somewhat pear-shaped, not well stained and with a 
 distinct nucleus in the corner (characteristic of mucous 
 cells). One or more of the second kind may be seen at the 
 periphery of an alveolus ; having well stained, granular 
 protoplasm and a cetvtrally placed nucleus — the demi- 
 lunes. 
 
 2. Serous gland; parotid gland of dog; logwood, C. 
 Balsam. 
 
 Examine under L.P. for ducts, alveoli, etc., as above. 
 ^ H.P. Ducts have same structure as before. The 
 alveoli are formed by groups of one kind of cell ; each 
 having well stained, granular protoplasm with a centrally 
 placed nucleus (characteristic of seroibs cells). 
 
 Compare well the two classes of mucous and serous 
 cells. 
 
 IV. Tonsas. 
 
 1. Section of human tonsil; logwood, C. Balsam. 
 
 L. P. The epithelial coat may be seen, under which lies a 
 layer of connective tissue throwing off many branches, 
 while beneath the connective tissue are mucovs glands 
 and numerous circular patches, the lymph follicles. 
 
 H.P. Examine the character of each of these struc- 
 tures ; particularly the follicles, built of adenoid tissue 
 enclosing leucocytes with well stained nuclei. 
 
 V. (Esophagus. 
 
 1. Rabbit, transverse section : logwood, C. Balsam. 
 
 L.P. Note the three distinct coats (1) epithelial, 
 (2) sub-epithelial, (3) muscular. 
 
 H.P. Epithelial coat formed of stratified epithelium, 
 cells nucleated and passing from lower columnar to 
 superficial flattened ones; lower border has a wavy 
 outline. 
 
 Sub-epithelial coat formed of connective tissue, contain-* 
 ing numerous blood-vessels. 
 
32 ALIMENTAEY CANAL. 
 
 The muscular coat is formed of layers of striated 
 muscle (being from the upper portion of the oesophagus) 
 embedded in connective tissue. 
 2. Dog. Transverse section ; carmine, C. Balsam. Similar 
 to that of the rabbit, but the sub-epithelial coat contains 
 a number of mucous glands opening by ducts upon the 
 surface. 
 
 YI. Stomach, 
 
 1. Cardiac end; dog; carmine, C. Balsam. 
 
 L.P. Four distinct coats (1) mitcous membrane, 
 (2) sub-mucous coat, (3) muscular coat of several layers, 
 (4:) external coat. 
 
 Examine carefully each coat under H.P. 
 
 (1) Mucous coat. Formed of simple tubular glands 
 with fine adenoid tissue between them. They possess 
 three kinds of cells : columnar cells forming the mouth 
 and neck, with well stained nuclei placed towards the 
 base ; peptic (chief or central) cells, forming the prin- 
 cipal part of the remainder of the gland, are well 
 coloured granular cells, each with a central nucleus ; ovoid 
 (parietal) cells, less in number, are mixed with the peptic 
 cells, but chiefly at the junction of the latter with the 
 columnar ; they are oval and possess large oval nuclei. 
 The muscularis mucosce, formed of a thin layer of un- 
 striated muscular tissue, is placed at the base of the glands. 
 
 (2) Sub-raucous coat : formed of fine areolar tissue, 
 containing numerous blood vessels. 
 
 (3) Muscular coat : possesses three distinct layers of 
 unstriated muscular fibres, the transverse, oblique, and 
 longitudinal. 
 
 (4) External coat shows as a clear outline (section of 
 endothelial cells) between which and the muscular coat 
 lies some fine connective tissue. 
 
 2. A similar section, stained with aniline blue, is to be 
 mounted in glycerine, and examined under H.P., when 
 the ovoid cells, which stain well, may be distinguished 
 from the chief or peptic cells. 
 
 3. Pyloric end; dog, logwood, C. Balsam. 
 
 L.P. shows the same coats as with the cardiac end, 
 but the glands are more branched, and have longer ducts 
 with wider mouths. 
 
ALIMBNTAET OANAl. 33 
 
 H.P. The glands are built of iwo kinds of cells, viz., 
 the columnar cells, lining the ducts and similar in cha- 
 racter to those at the cardiac end ; and cells which do 
 not stain well, are more cubical, and have their nuclei at 
 the periplieral portion. This part of the gland is often 
 seen cut transversely, and has a good amount of fine 
 connective tissue sun-ounding it. 
 
 VII. Small Intestine. 
 
 1. Transverse section ; dog, logwood, C. Balsam. 
 
 L. P. Note the four coats, similar tothoseof the stomach 
 except that the muscular one is formed of only two layers, 
 viz., the internal circular and external longitudinal (which 
 in this specimen will show their fibres cut respectively 
 longitudinally and transversely). The mucous coat con- 
 tains simple glands, glands of Lieherhiihn, and projections, 
 the villi. In the upper part of the small intestine may 
 be seen, in addition to the above, Briinner^s glands, 
 compound glands whose acini lie in the submucous coat, 
 and whose ducts pierce the muscularis mucosae to open 
 on the surface. ' 
 
 H.P. Each villus is formed of a core of adenoid tissue 
 containing fine hlood vessels and a lacteal in the centre, 
 indicated by fine lines. It is covered by a single layer 
 of columnar epithelium cells, which are granular, have a 
 distinct nucleus and fine clear ouier border; many undergo 
 mucous degeneration and form swollen, unstained goblet 
 cells, the nuclei being pressed to the edge. The glands 
 of Lieherhiihn are simple crypts, formed of cells showing 
 a distinct nucleus. Beneath these glands is the muscu- 
 laris mttcosce. 
 
 The characters of the .other layers are similar to those 
 described for the stomach. 
 
 2. Tease in normal saline a small piece of mucous mem- 
 brane from the frog's intestine, and study the characters 
 of the columnar, goblet and gland cells described above. 
 
 3. Section of mucous membrane, parallel to the surface, 
 ■ from dog ; logwood, C. Balsam. 
 
 H.P. shows transverse sections of glands of LieherhUhn, 
 with the lumen surrounded by cells and the interglandular 
 adenoid tissue. In many places the glands have slipped 
 
34 tlVER. 
 
 out, showing only the adenoid tissue and a space. Trans- 
 verse sections of villi may at times occur. (Section to be 
 compared with a tangential one from the medulla of the 
 kidney.) 
 4. Peyer's patch ; logwood, C. Balsam. 
 
 L.P. shows the villi and glands of the small intestine, 
 but la the tissue of the mucous layer lie several masses 
 of adenoid tissue, round iu shape, causing a bulging of the 
 mucous membrane, and not covered by villi or glands. 
 When they occur alone they are called solitary glands. 
 
 VIII. Large Intestine. 
 
 1. Transverse section; dog; logwood, C. Balsam. 
 
 L.P. shows coats similar to those of the small intestine, 
 but with no villi and no Brunner's glands. 
 
 H.P. The glands are the same in structure as the 
 glands of Lieherhiihn ; they contain generally a greater 
 number of goblet cells. 
 
 XI.-LIVEE. 
 
 I. Fresh Liver. 
 
 1. Gently scrape the cut surface of a fresh rat's liver and 
 mount in normal saline ; examine under L.P. and H.P. 
 
 Disregarding the number of blood corpuscles, carefully 
 study the hepatic cells ; note their very granular proto- 
 plasm with no cell wall, their polygonal shape and centrally 
 placed nucleus : sketch. 
 
 Run in a little 1 % acetic acid to bring out the nuclei 
 distinctly. 
 
 2. Scrape and mount in a similar manner the hepatic cells 
 from a frog's liver. Note with H.P. the large and small 
 fat globules they contaiiL 
 
 II. Hardened Liver. 
 
 1. Pig's liver ; logwood, C. Balsam. 
 
 L.P. Note the polygonal hepatic lobules (very dis- 
 tinctly marked in the pig) surroimde(| by connective 
 tissue forming the capsule of Glisson, which is continuous 
 
LUNG. 35 
 
 with the outer coat of the liver. Within this tissue and 
 between the lobules lie : the interlobular veins (branches 
 of the portal vein) with large lumen but thin walls : the 
 fine branches of the hepatic arteries having small lumen 
 but stout walls : and the hile ducts lined with columnar 
 epithelium. In the centre of the lobules lie the intra- 
 lobular veins, and at parts the large stMobular veins may 
 be seen in section. 
 
 H.P. The polyhedral hepatic cells with their nvdei 
 are stained by the logwood j note their radial arrange- 
 ment from the intralobular veins towards the circum- 
 ference of the lobule, with the (crushed) capillaries be- 
 tween them (c/. injected specimen). The coats of the 
 arteries, veins and ducts may be distinctly seen and 
 studied. 
 2. Dog's liver ; logwood and C. Balsam. 
 
 Examine under L.P. and H.P. for parts described 
 above ; note the small amount of interlobular connective 
 tissue, which is here found chiefly round the branches 
 of the portal vein (interlobular), hepatic artery and 
 duct : these three run together as in the pig. The 
 intralobular join to form the svblobular, which join to 
 form the hepatic veins. 
 
 III. Injected Liver. 
 
 Rabbit, injected with carmine ; mount in C. Balsam. 
 
 Study under L.P. the interlobular and intralobular 
 veins and then under H.P. their connection by the 
 capillaries, between which lie the hepatic cells. 
 
 XII.-LUNG. 
 I. Trachea. 
 
 1. Transverse section ; pioro-carmine, C. Balsam. 
 
 L.P. Note the following layers — (1) Epithelial layer, 
 (2) Connective tissue, (3) Inoonr^Bie ring of cartilage ^omsA. 
 at the ends by unstriated muscle fibres, (4) Connective 
 tissue. 
 
36 LUNG. 
 
 Carefully examine the various layers under H.P. 
 
 1. Epithelium; stratified, the outer cells being colum- 
 nar and ciliated; beneath these lie some fine adenoid 
 tissue and a layer of yellow elastic fibres, the latter run 
 longitudinally and therefore appear in transverse section 
 {fj. connective tissue, page 13). 
 
 2. Connective tissue ; this holds mucous glands which 
 open upon the surface by diicfs. The tissue becomes 
 denser on approaching the cartilage rings. 
 
 3. Cartilage rings; are formed of hyaline cartilage, 
 the cells being closely grouped. The ends of the rings 
 are joined by unstriated muscle fibres, arranged trans- 
 versely. 
 
 4. Connective tissue ; very fibrous close to the cartilage 
 rings, and holds numerous blood vessels. 
 
 2. Longitudinal section ; logwood, C. Balsam. The section 
 is carried some distance so as to inclade several cartilage 
 rings, and is to be carefully compared with the transverse 
 section, particularly with regard to the layer of elastic 
 fibres under the epithelium. Examine the parts 
 mentioned in the former section, under L.P. and H.P. 
 
 II. Lung, 
 
 1. Stained mammalian Iting; section, carmine, C. Balsam. 
 
 L.P. Note the sections of arteries, veins, bronchial iubes, 
 and general lung tissue. 
 
 H.P. The bronchial tubes possess the same coats as 
 the trachea, but differ, firstly in the cartilage being 
 arranged in irregular pieces round the tube, and secondly 
 in the unstriated muscle forming one continuous riri^ 
 round the tube, lying just beneath the layer of yellow 
 elastic fibres. 
 
 Next to the sections of large bronchial tubes, those of 
 the arteries and veins appear. 
 
 The general lung tissue shows sections of the alveoli 
 lined by a single layer of epithelial cells, whose nuclei 
 stain well and appear either in section, or in the cell 
 when the side of an alveolus can be seen superficially. 
 Between neighbouring alveoli (crushed) blood capillaries 
 appear, also some very fine connective tissue. 
 
LYMPHATIC SYSTEM; 37 
 
 2. Unstaiiied mammalian lung, glycerine. Study the 
 same parts of this section under L.P. and H.P. 
 
 3. Injected lung (carmine injection) mount in C. Balsam, 
 
 Examine under L.P. and H.P. to show the arrangement 
 of blood vessels and capillaries on the walls of the alveoli ; 
 the capillaries are large, freely anastomose, and leave 
 but small spaces between them. 
 
 4. Newt's lung; gold preparation, mount in glycerine. 
 This is to demonstrate the epithelium lining the lungs. 
 
 XIII.-LYMPHATIC SYSTEM. 
 
 I. Lymphatic Vessels (demonstrations). 
 
 1. Lymphatics of diaphragm (rabbit ; pleural side), silver 
 preparation. 
 
 With L.P. note the numerous inter-communicating 
 light spaces (compared with the tint of the other tissues) 
 — ^the lymphatic vessels. 
 
 H.P. The vessels are seen to be lined by a single 
 layer of endothelial cells, similar to those seen in the 
 silver preparation of blood vessels in the frog's bladder. 
 In the larger vessels transverse lines, indicating the 
 valves, may be seen. 
 
 2. Septum cystemae lymphaticae magnsB of the frog; 
 prepared with silver nitrate. 
 
 Under H.P. by alteration of the focus, two layers of 
 endothelial cells may be seen, one covering the membrane 
 on the side towards the posterior lymph sac, the other 
 on the side towards the peritoneal cavity. At certain 
 points distinct openings or stomata appear, allowing 
 communication between the above cavities, they are 
 surrounded by a layer of granular cells. The wavy out- 
 lines of the endothelial ceDS are to be noticed, and also 
 the small, dark, irregular patches sometimes found at the 
 junction of the cells, the pseudostomata. 
 
38 LYMPHATIC SYSTEM. 
 
 II. Lymphatic Glands. 
 
 1. Simple. Examine the sections of the tonsils (p. 31) or 
 Peyer's patch, p. 34). Note the circular mass of adenoid 
 tissue (lymphoid tissue) denser towards the periphery, 
 and enclosing in the meshes leucocytes, whose nuclei 
 stain well. 
 
 2. Compound; dog; logwood, C. Balsam. 
 
 L.P. The gland is surrounded by a capsule of fibrous 
 tissue, sending in traheculce, which in the outer portion 
 or cortex of the gland are radial, but in the inner portion 
 or medulla form an irregular meshwork. The substance 
 of the gland is composed of adenoid tissue, which towards 
 each trabeoula is less dense in form, contains but few 
 leucocytes and stains lightly, the lymph sinus ; but fur- 
 ther away it is denser, well filled with leucocytes and 
 stains deeply. 
 
 H.P. The capsule and trabeculse are seen to be 
 composed of fhrons tissm, and contain some fibres of 
 unstriated muscle. In the lymph sinus carefully note the 
 branching, nucleated cells forming the adenoid tissue with 
 but few leucocytes in the meshes; also the numerous 
 leucocytes in the denser portions. 
 
 Demonstration. 
 
 Silver and logwood preparation of lymphatic gland, to 
 show the endothelial cells covering the trabeculse. 
 
 III. Thymus Gland. 
 
 1. From child ; logwood, C. Balsam. 
 
 L.P. shows a capsule of fibrous tissue sending in septa, 
 which divide the body into lobules and again miofollides. 
 
 H.P. The follicles are separated by these fine septa, 
 and consist of adenoid (or retiform) tissue containing 
 leucocytes. The adenoid tissue is dense towards the outer 
 portion or cortex of each follicle, but less dense at the 
 medulla; here are found small bodies, which show a 
 concentric striation and nuclei, they are called the 
 concentric corpuscles of ffassall. 
 
SPLEEN. — ^DUCTLESS GLANDS. 39 
 
 XIV.-SPLEEN. 
 
 Spleen of cat ; logwood, C. Balsam. 
 
 L.P. shows a fibrous capsule, which throws in mimerous 
 trabeeulcB dividing the spleen into irregular spaces ; the 
 latter are filled with the splenic pulp which has a blue 
 and red appearance, the former due to the staining, the 
 latter to the presence of blood. Round masses of a pure 
 blue tint, Malpighian bodies, are distributed about the 
 spleen substance. 
 
 H.P. The capsule (covered on the outside by a layer 
 of endothelial cells, whose nuclei may be seen) and the 
 trabeculse are formed oi fibrous tissue, with some unstri- 
 ated muscle fibres and blood vessels seen in section. 
 
 The splenic pulp is of adenoid tissue, whose meshes are 
 flUed with red corpuscles and leucocytes (latter stained by 
 the logwood.) 
 
 The Malpighian bodies are also buUt of adenoid 
 tissue, denser towards their periphery, but the meshes 
 simply contain leucocytes — hence their white colour in an 
 unstained section and pure blue in the logwood stained 
 one ; in these bodies sections of blood vessels may be seen. 
 
 XV.-THE DUCTLESS GLANDS. 
 
 I Snprareual Capsule. 
 
 1. Han ; logwood, C. Balsam. 
 
 L.P. shows a capsule and a body divided into a cortex 
 and medulla. 
 
 H.P. The capsule is of fibrous tissue throwing in a 
 number of fine branches. 
 
 The cortex consists of three parts ; the oitter zone, of 
 well nucleated cells, collected in small masses ; a middle 
 zone of columns of cells in cylindrical masses; the inner 
 zone of irregularly grouped cells. 
 
 The medulla consists of masses of cells, embedded in 
 connective tissue, with numerous blood vessels. 
 
40 KIDNEY. 
 
 t Sm^^' }<^o"iP8^e with above. 
 
 II. Thyroid Gland. 
 
 1. Hnman ; logwood, C. Balsam. 
 
 L.P. shows a capsule which throws in branches to 
 divide the gland into lohes and lobules. 
 
 H.P. The lobules contain closed vesicles, varying in 
 size and shape, but all lined by a single layer of nucleated 
 flat cells which rest on a basement membrane. Fine 
 connective tissue is found between the vesicles ; these may 
 contain a stained substance, due to the hardening of the 
 contents during preparation. 
 
 XVI.-KIDNET. 
 
 I. Radial Section. 
 
 Eadial Section of the Kidney of a small animal 
 (guinea-pig), logwood, G'. Balsam. 
 L.P. shows the kidney divided into two parts, viz. : — 
 
 1. Cortical portion, having an irregular appearance, 
 from the convoluted tubes and the glomeruli; at intervals 
 bundles of straighter tubules radiating towards the 
 surface may be seen, the medullary rays. 
 
 2. Medullary portion, having a radial striation from 
 the arrangement of the collecting tubules, which join 
 dichotomously ; it is divided into pyramids of Malpighi, 
 upon the surfaces of which the tubules open into the 
 pelvis (or calices and so to the pelvis) from which 
 originates the ureter. (The tiibules forming the medul- 
 lary portion may have been cut transversely, and the 
 radial arrangement not be so distinct). 
 
 II. Cortex. 
 
 1. Badial section; dog, carmine, C. Balsam. 
 
 L.P. Note the outer capside of the kidney; the 
 general irregular arrangement of the tubules, which, 
 
KIDNEY. 41 
 
 however, at intervals shows tracts of more parallel 
 arrangement running radially, the medullary rays ; and 
 the well stained Mdlpighian corpuscles, 
 
 H.P. The various parts are connected by fine areolar 
 tissue, continuous with the fibrous capsule. Each 
 Malpighian corpuscle consists of an outer capsule of 
 nucleated, flat epithelial cells, and contains a bunch of 
 capillaries forming the glomerulus ; it opens by a narrow 
 neck into the proximal convoluted tidmle, which with the 
 distal convoluted tubule form the chief structures of the 
 cortex. The epithelium of each convoluted tubule is 
 nucleated, granular at the inner portion and somewhat 
 striated at the outer one. The distal convoluted tubules 
 are connected by junctional tubules with the collecting 
 ones ; these show clear nucleated ceUs. 
 , Divide a fresh kidney, gently scrape the cut surface 
 of the cortex, mount these scrapings in normal saline 
 and study vmder the H.P. for the various cells described 
 above. 
 
 III. HedtiUa. 
 
 1. Badial section ; logwood, C. Balsam. 
 
 L.P. The chief part is formed of the collecting 
 tubules, which join dichotomously and open upon the 
 surfaces of the pyramids of Malpighi. 
 
 H.P. The collecting tubules, which show a clear 
 lumen, are formed of clear, micleated, cubical cells, be- 
 coming columnar as they approach the apex of the 
 pyramid. In that portion of the section towards the 
 cortex are the looped tuples of Henle (which join the 
 proximal and distal convoluted tubules) each formed of 
 a narrow descending limb and a broader ascending limb ; 
 the epithelium of the former is clear, very flat with 
 prominent nuclei j that of the latter is granular, 
 nucleated, and at times imbricate. 
 
 2. Tangential section ; logwood, C. Balsam, 
 
 Under H.P. study the various tubtdes and the 
 character of their cells. In many cases the cells will 
 have dropped out and the connective tissue is well seen. 
 (Compare with the transverse section of the glands of 
 Lieberkuhn p. 33). 
 
42 
 
 KIDNEY. 
 
 3. Fresh kidney ; examine in normal saline under H.P^ 
 some scrapings from the medullary portions. 
 
 IV. Injected Kidney. (Blood vessels with carmine.) 
 
 Radial section, mount in G. Balsam. 
 
 L.P. Note the interlobular arteries running radially 
 from the junction of the cortex and medulla towards the 
 capsule, and giving off an afferent vessel to each Malpighian 
 corpuscle, where it breaks up into the glomerulus. From 
 this emerges an efferent vessel which breaks up again into 
 a second system of capillaries, joining with those of other 
 efferent vessels round the convoluted tubules ; these 
 finally collect to form an interlobular vein which runs 
 parallel to an interlobular artery. The medulla is sup- 
 plied by arterice rectce which originate from the same 
 branches of the renal artery that give rise to the inter- 
 lobular arteries. 
 
 V. Bladder and Ureter. 
 
 1. Bladder ; dog, logwood, C. Balsam. 
 
 L.P. shows three coats : the mucous, sub-mucous, and 
 muscular coats. 
 
 H. P. The mucous coat is formed of stratified epithelium, 
 the upper somewhat cubical, lower columnar or pear 
 shaped cells ; but the cells, fitting into one another, have 
 an irregular appearance in section. The sub-mucous coat 
 is formed of connective ti,ssue and contains many Mood 
 vessels, seen in section. The muscular coat is formed of 
 unstriated muscle fibres, placed in several layers separated 
 by connective tissue. 
 
 2, TJreter ; transverse section ; logwood, C. Balsam. 
 
 L.P. shows similar coats to the bladder, but themuscular 
 coat is distinctly divided into three layers, two with the 
 fibres longitudinally arranged, and one, middle one, with 
 circular fibres. 
 
 Examine the parts under H.P. 
 
SMn. 
 
 SKIN AND HATB. 43 
 
 XVII.-SKIN AND HAIR. 
 
 1. Vertical section from the tip of a finger ; logwood, C. 
 Balsam. 
 
 L.P. Note the division into two distinct layers; 
 the epidermis which is again divided into an upper 
 faintly stained part, and a lower deeply stained part 
 and the dermis. 
 
 Study these various layers under the H.P. 
 
 Epidermis consists of several layers, viz. : 
 
 1. Stratum corneum (or horny layer). The cells are 
 not distinguished as separate, are but very faintly stained, 
 and with no nuclei visible. 
 
 2. Stratum lucidum, a clear narrow layer, formed of 
 few cells, with stained flattened nuclei. 
 
 3. Stratum Malpighii (or rete mucosum) stains well, 
 consisting of several layers of cells distinctly nucleated ; 
 the lower ones are somewhat columnar and arranged in ia 
 wavy line, being on the surfaces of the papillae. 
 
 Dermis (cutis vera or corium). This gradually 
 passes into the sub-cutaneous tissue. It is formed of 
 dense areolar tissue, which is continued up into small 
 prominences under the epidermis, called papillce ; some 
 of these contain small oval bodies with well stained 
 transverse nuclei, the Tactile corpuscles. 
 
 In the lower portions of the connective tissue fat cells 
 and h'ood vessels are freely distributed. 
 
 Through the epidermis may be seen spiral ducts, 
 leading to coiled tubes formed of cubic nucleated cells 
 placed in the sub-cutaneous tissue, the sudoriferous or 
 sweat glands. Again in some the lowest portions 
 show sections of Pacinian bodies, appearing as oval 
 masses of concentric lines. 
 
 2. Skin of negro, stain with eosin, C. Balsam. 
 
 Notice the same parts as in the above section, but 
 also the presence of pigment granules in the lower 
 cells of the epidermis. 
 
 3. Nail ; transverse, vertical section ; logwood, C. Balsam. 
 
 Note the thickening of the stratum corneum to form the 
 nail, and the long papiUee of the dermis. 
 
44 
 
 BEm AND HAIB. 
 
 a hair from the head and mount in C. 
 
 II. Hair 
 
 1. Remove 
 Balsam. 
 
 L.P. shows the stem generally surrounded at its base 
 by the root sheath removed from the hair follicle. 
 
 H.P. The hair consists of (1) Gviicle, a layer of 
 imbricate, epidermic cells, giving a saw-like appearance 
 to the edge. (2) Cortex, appearing homogeneous with a 
 few longitudinal striations and containing fine pigment 
 granules. (3) Pith or marrow, with fine air-spaces. 
 
 2. Rabbit, mount in C. Balsam. 
 
 Note the regular arrangement of the cavities in the 
 pith and the small amount of cortex. 
 
 3. Compare specimens from Sheep and Rat with the above. 
 
 4. Verticle section of hair follicle; logwood, C. Balsam. 
 
 L.P. shows the hair stem arising from the hair-hM 
 surrounding a papilla, and passing out of the hair 
 follicle by the mouth. This follicle dips down below the 
 epidermis and may have a sebaceous gland opening into it. 
 H.P. The foUiole consists of parts corresponding to 
 the dermis and epidermis, which are arranged as 
 follows, travelling from the cutis vera towards the 
 hair : — 
 
 ' (a) Outer sheath of the hair sac ; longitudinal 
 
 closely packed fibres, running parallel to the 
 
 hair. 
 
 ■ (6) Inner sheath of the hair sac ; transverse 
 
 fibres, therefore cut across. 
 
 (c) Hyaline layer ; clear layer separating dermic 
 
 and epidermic portions. 
 (a) Outer root sheath ; mass of irregular cells, 
 
 continuous with the rete mucosum. 
 (6) Inner root sheath, corresponds to the horny 
 layer. Consists of two sets of cells, viz., 
 Henle's layer, of flat irregular non-nucleated 
 cells, and Huxley's layer, of flat nucleated cells. 
 
 (c) Cuticle of the root sheath ; a layer of imbricate 
 cells in contact with those of the hair. 
 
 (d) Hair, with its various parts in section. 
 Transverse section of hair follicle; logwood, C. Balsam. 
 
 Examine well under L.P. and H.P., comparing with 
 the parts described above. 
 
 .a 
 
 > 
 o 
 o 
 
 o 
 
 • l-l 
 
 a 
 
 t 
 
 o 
 o 
 
 a 
 
 • •-I 
 
1TB. 45 
 
 XVIII.-ETE. 
 
 I. Cornea. 
 
 1. Vertical section ; logwood, C. Balsam. 
 
 L.P. The anterior deeply stained line is the epi- 
 
 thelium continuous with that of the conjunctiva; the 
 
 general body of the cornea is not well stained ; the thin, 
 
 well stained line is the epithelium of the anterior 
 
 - chamber. 
 
 H.P. Examine the characters of the various layers, 
 passing from the exterior. 
 
 1. Epithelium ; this is stratified, the inner cells being 
 columnar, nucleated, and gradually passing to the 
 flattened superficial ones. 
 
 2. Anterior hyaline layer, clear with no striations. 
 
 3. Corneal substance; formed by lamellse of fibrous tis- 
 sue placed at right angles in alternate layers, so appearing 
 in longitudinal and transverse sections ; between these 
 layers are the well stained corneal corpuscles, appearing 
 in rows. 
 
 4. Membrane of Descemet or Demours (posterior hyar 
 line membrane) is clear and has a distinctly marked out- 
 line. 
 
 5. Epithelium of the anterior chamber, is formed of a 
 single layer oiflat cells, showing distinct nuclei. 
 
 2. Examine the gold preparation of the frog's cornea 
 (page 14) for the corneal corpuscles. They are flat, 
 angular in shape, nucleated, and throw ofi' numerous 
 branches. 
 
 II. Iris, etc. 
 
 1. Junction of iris, sclerotic and cornea, in section ; log- 
 wood, C. Balsam. 
 
 L.P. Carefully note the relation of these parts. 
 
 The cornea at its junction with the sclerotic has its 
 external epithelium continued as a finer band over the 
 conjunctiva, which is of fine areolar tissue. 
 
 At the connection of the cornea and sclerotic with the 
 iris, are seen the spaces of Fontana, bounded by the liga- 
 mentum pectinatum iridis from the anterior chamber. 
 
46 EYE. 
 
 Anterior to these spaces lies the canal of Schlemm, seen 
 in section, while , posterior and to the side is the ciliary 
 
 The iris is continuous with the choroid coat, showing 
 the ciliary processes in section at their junction, and has 
 a layer of pigment cells. 
 
 H.P. The sclerotic is composed of fihrous connective 
 tissue, which becomes lighter towards the conjunctival 
 portion. The character of the layers of the cornea may 
 be well seen ; also, its lining of epithelial cells over the 
 membrane of Descemet. 
 
 The light tissue of the ciliary processes may be dis- 
 tinguished, with their dngle layer of pigmented epithe- 
 lium, the pigment being placed at the base of the cells 
 which show a clear outline. Examine for the ciliary 
 muscle of un^nated fibres. 
 
 The iris with its pigmented connective tissue is covered 
 anteriorly with a single layer of cells continuous round 
 the edge with the posterior pigmented layer, they are 
 also continuous with that layer placed on the membrane 
 of Descemet in the cornea. Towards the edge of the iris 
 the sphincter muscle appears clearly; the unstriated 
 fibres showing in transverse section with distinct nuclei. 
 Throughout the section numerous blood vessels appear, 
 
 III. Lens. 
 
 1, Tease in glycerine a small piece of the lens treated for 
 two or three days in -J % potassium bichromate. 
 
 H.P. Notice the fibrous structure of this body, the 
 JWres being long and with serrated edges. 
 
 2. Section; glycerine. 
 
 H.P. The thin, flat fibres forming the substance of 
 the lens, are seen to be placed in concentric lamellse. 
 When the capsule is present it appears as a clear, thin 
 layer. 
 
 IV. Setina. 
 
 • 1. Pig's retina, section; logwood, C. Balsam. 
 , With H.P. note the following layers. 
 
 1. Nerve fibres; form a layer lined inside by the 
 internal limiting membrane. At different points sections 
 of small blood vessels appear. 
 
OLTACTORT MUCOUS MEMBRANE, ETC.' 47 
 
 2. Nerve cells ; forming a distinct layer, are multipolar 
 and show clearly their nuclei and nucleoli. 
 
 3. Inner molecular layer has a granular appearance. 
 
 4 Inner nuclear layer ; well stained cells, spindle- 
 shaped with distinct nuclei, may be seen in several rows. 
 
 5. Outer molecular layer; thin layer, having a similar 
 appearance to 3, not well stained. 
 
 6. Outer nuclear layer ; like 4 is formed of well stained 
 spindle shaped nucleated cells, in several rows. 
 
 7. External limiting membrane, appears as a clear line 
 outside which lies — 
 
 8. The layer of rods and cones, which in this prepa- 
 ration are not distinct. 
 
 Stretching directly across this section from the in- 
 ternal limiting membrane Mullet's fibres, with a clear 
 outline, may be distinctly seen. 
 
 , Prog's retina ; prepared with osmic acid, tease in gly- 
 cerine. 
 
 H.P. shows the rods distinctly, which break up into a 
 long, clear, outer portion and a smaller, granular, inner 
 portion. 
 
 , Figment layer. Given as a specimen of epithelium 
 (page 12). 
 
 In some sections of retina the pigment layer appears ; 
 the cells throw numerous processes between the rods 
 and cones, in which processes and the lower part of 
 the cells the pigment granules collect, leaving a clear 
 outer hyaline border. 
 
 XIX.-OLFACTOBY MUCOUS MEMBRANE, etc. 
 
 I. Olfactory Mucous Membrane. 
 
 I. Guinea-pig, section; logwood, C. Balsam. 
 
 L.P. shows an epithelial layer resting upon a basement 
 membrane, and covering fine connective tissue containing 
 glands (of Bowman) and nerve fibres. 
 
48 BRAIN AND SPINAL COED. 
 
 H.P. Epithelium is seeu to consist of several layers ; 
 theupper cells are coZMOTMarwithwellstained nuclei ; below 
 these (more clearly seen where the epithelium is slightly 
 broken up) are several layers of well nucleated spindle- 
 shaped cells, sending up processes between the columnar 
 ones. 
 
 The glands are serous, with distinctly nucleated cells. 
 
 2. Tease in glycerine a piece of the membrane from a 
 
 guinea-pig, treated for 24 hours in Ranvier's alcohol, 
 
 and stained with carmine. H.P. Study the above cells 
 
 separated. 
 
 II. Tactile Corpuscles and Pacinian Bodies. 
 
 Examine the sections of skin (page 43). 
 Demonstrations. 
 
 1. Osmic acid preparations of skin to show the tactile 
 corpuscles. 
 
 2. Silver preparations of Pacinian bodies to show the 
 endothelial nature of their coats. 
 
 III. Taste Buds. 
 
 1. Babbit's tongue ; papilla foliata ; logwood ; C. Balsam. 
 
 L.P. The epithelium is in folds, covering a mass of 
 striated muscle embedded in connective tissue. On each 
 side of these crypts, well stained oval buds may be seen, 
 taste hvds. 
 
 H.P. Carefully examine the buds. The general epi- 
 thelial cells flatten as they approach them. The 
 buds show an outer layer of nucleated cells, containing 
 a bundle of ta^te cells which are spindle shaped with oval 
 nuclei. At points the spaces containing these cells will 
 show a small openinff into the crypt. 
 
 XX.-BRAIN AND SPINAL CORD. 
 
 I. Spinal Cord. 
 
 1. Cervical region of deg ; logwood, clear in turpentine and 
 kreosote ; mount in C. Balsam. 
 
 L.P. The cord, surrounded by a layer of fine connec- 
 tive tissue the pia mater, is divided into right and left 
 
BRAIN AND SPINAL CORD. 49 
 
 halves by the broad, shallow anterior fissure (into which 
 dips the pia mater) and the narrow, deep posterior fissure. 
 
 The outer portion of the cord is formed of white 
 substance, which on each side consists of three divisions, 
 viz., the anterior, lateral and posterior columns (the latter 
 again being divided into two by a fine wedge of connective 
 tissue called the slender fasciculus, peculiar to the 
 cervical region). 
 
 The grey matter of the spinal cord has the shape of the 
 letter H ; each half of the cord possessing an anterior and 
 a posterior eornu, joined across the median line with those 
 of the opposite side, by the grey commisure ; the latter 
 shows in section the central canal. Each anterior cornu 
 is broad and gives off its nerve fibres to the anterior root 
 of the spinal nerve by several small bundles, while the 
 posterior cornu is narrower and sends off its nerves by 
 one compact mass : at this latter point the cornu has a 
 light appearance, the substantia gelatinosa. The portion 
 of the grey commisure behind the central canal is called 
 the posterior grey commisure ; that before it, the anterior 
 grey commisure; while between the latter and the anterior 
 fissure the white commisure is found, lightly stained. 
 
 H.P. The pia mater is of fine conneAive tissue con- 
 taining numerous blood vessels. 
 
 The white matter is chiefly formed of medullated nerve 
 fibres, seen principally in transverse section, with well 
 stained axis cylinders ; supporting these fibres is a very 
 fine mass of (modified connective) tissue, neuroglia, cells 
 of which may be seen stained, it is collected in a good 
 layer just beneath the pia mater and also in the 
 substantia gelatinosa. 
 
 The grey matter consists of medullated and non- 
 meduUated nerve fibres and nerve cells, held by neuroglia. 
 The cells are multipolar, each having a distinct nucleus 
 and nucleolus, and are larger in the anterior than in the 
 posterior comua. The central canal is lined by a layer 
 of columnar epithelium. 
 . Dorsal region ; prepared from the same dog and mounted 
 as before. 
 
 L.P. Compared with the cervical region, the section 
 is smaller, and the quantity of white matter is smaller 
 in proportion to the grey. 
 
50 BRAIN AND SPINAt CORD. 
 
 Study under both powers the parts described in the 
 cervical region and note Glarke's column, a small 
 collection of large cells, outside a.nd posterior to the 
 central canal. 
 
 3. lumbar region, mounted by the same method. 
 
 Under both powers work as before ; the proportion of 
 white matter is still less compared with the grey ; the 
 cornua are large. 
 
 4. Lumbar region of spinal cord of ox; transverse section; 
 aniline blue, glycerine. 
 
 Use L.P. and H.P. Note the fine neuroglia, which 
 is very distinct in the white substance, with the 
 numerous meduUated nerve fibres having well stained 
 axis cylinders. The multvpolar nerve cells with their 
 nuclei and nucleoli are very large in the anterior cornua. 
 
 II. Cerebellum. 
 
 1. Vertical section; logwood, C. Balsam. 
 
 L.P. Note the primary and secondary folds forming 
 the folia or leaflets. Grey matter (outside) is covered 
 by pia mater, and consists of : — 
 
 1. An outer, broad layer showing a few stained points. 
 
 2. An inner, well stained granular or nuclear layer. 
 The white matter, enclosed in a fold of grey matter, is 
 
 formed of numerous medullated nerve fibres. 
 
 H.P. The outer, broad layer of the grey matter shows 
 a matrix with numerous fibres, and at parts stained nuclei; 
 of the inner, nuclear layer the nuclei are very numerous. 
 At the line of junction of these two layers is a single row 
 of large, multipolar nerve cells, the ganglion cells of 
 PiM-hinje, each of which possesses a distinct nucleus and 
 nucleolus, and sends a fine single branch inwards to dis- 
 appear ill the nuclear layer, and a branch outwards which 
 breaks up into numerous filaments in the outer layer. 
 
 III. Cerebrum. 
 
 1. Vertical section; carmine, C. Balsam. 
 
 L.P. shows the folds to be simple, and to consist of 
 an outer grey and inner white matter. 
 
 H.P. Grey matter contains numerous multvpolar nerve 
 cells with nuclei and nucleoli; these at times may, be 
 distinguished as forming several layers, difiering accord- 
 ing to the size and number of the cells. 
 
0EGAN3 OF REPRODUCTION. 51 
 
 XXI.-ORGANS OP REPRODUCTION. 
 
 I. Male. 
 
 1. Testis of dog. Make a section passing through, the 
 tubuli seminiferi, epididymis and vas deferens, near the 
 globus major : logwood, mount in C. Balsam. 
 
 L.P. Note the visceral portion of the tunica vaginalis, 
 within which lies the tunica alhuginea throwing in 
 branches to support the convoluted tubuli seminiferi 
 and becoming thicker at the connection with the epidi- 
 dymis. The tubes of the latter are readily seen by their 
 clear lumen and regular, nucleated cells. The vas 
 deferens appears as a tube in transverse section, having 
 a large lumen and surrounded by muscular fibres. 
 
 Under H.P. the tunica vaginalis has a clear outline 
 (section of the endothelial cells lining the sac), it is 
 built of fibrous tissue showing many nuclei, and is named 
 the tunica adnata. 
 
 Within the above lies the tunica albuginea of fibrous 
 tissue, sending in numerous branches of fine connective 
 tissue between the tubuli seminiferi. Blood vessels are 
 seen in section. 
 
 The tubuli seminiferi, cut in various directions, con- 
 sist of several layers of seminal cells, granular, nucleated, 
 and differing according to the state of the gland ; those 
 cells nearest the lumen may be in the act of forming sper- 
 matozoa, hence called spermatoblasts. 
 
 The epididymis shows numerous sections of tubes 
 embedded in a good quantity of connective tissue. The 
 tubes of the epididymis possess a distinct coat of circular 
 muscular fibres, within this a basement membrane and a 
 layer of nucleated columnar epitheliu/m cells with long dlich 
 Beneath these columnar cells the nuclei of others, placed 
 on the basement membrane, may be seen. 
 
 The vas deferens is well embedded in connective tissue 
 showing numerous blood vessels; it possesses an external 
 longitudinal muscular layer and an internal circular mus- 
 cular layer of the unstriated variety. Upon a layer of 
 connective tissue is placed one of stratified columnar 
 epithelium, the columnar cells being towards the lumen. 
 
52 OEGANS OF EEPBODUCTION. 
 
 2. Tul)uli seminiferi of the rat. Stain the section with 
 logwood, and mount in C. Balsam. 
 
 L.P. Sections of the tubules separate, the amount of 
 connective tissue between them being very small. 
 
 H.P. Examine different sections for the spermatozoa 
 in various stages of development. The seminiferous 
 tubules have a basement membrane and several layers of 
 well nucleated seminal cells ; those cells at the base being 
 closely packed, while those near the lumen, the spermMo- 
 blasts, waicy in appearance. Some appear fan-like with nu- 
 merous short, well-stained rods, the heads of the spermar 
 tozoa ; other tubes have cells with fine radiating, thread- 
 like lines passing from these stained heads into the lumen, 
 and in some cases filling the latter. At parts the tubes 
 may have been crushed and the spermatozoa set free, the 
 latter showing a flat ellipsoidal head, a short middle 
 piece and a long tail. 
 
 3. Spermatozoa ; cut across the testis of a fresh-killed rat, 
 press the cut part on a slide, cover and examine under 
 H.P. Note the head piece, middle piece, and tail, also 
 the rapid movement due to the motion of the latter. 
 
 II. Female. 
 
 1. Ovary of cat ; logwood, C. Balsam. 
 
 L.P. The section is seen to have a clear outline except 
 at its attachment ; it consists of a stroma showing sections 
 of blood vessels. Graafian follicles of various sizes, and 
 possibly a corpus luteum. 
 
 H.P. The clear outline is due to a single layer of 
 short, columnar epithelium cells, the germinal epithelium, 
 beneath which lies a distinct layer of fibrous tissue, the 
 tunica aJbuginea. The stroma is formed of fibrous tissue 
 containing blood vessels, and passes gradually from the 
 tunica albuginea. 
 
 The Graafian follicles are found of various sizes ; the 
 smallest form a layer beneath the tunica albuginea, 
 staining less deeply than that coat. Those somewhat 
 larger show a distinct outline, the membrana propria, 
 within which lies a single layer of columnar epithelium, 
 the membrana granulosa ; the latter encloses the ovum 
 with its nucleus or germinal vesicle. 
 
ORGANS OF EEPEODUCTION. 53 
 
 The largest follicles have a good fibrous investment, 
 within which lies the memJbrana granulosa now many 
 cells deep and not filling the cavity *but throwing in a 
 projection, the discus proligerus, which encloses the 
 ovum. The ovum has a distinct, investing membrane, 
 the zona pellucida, and shows the germinal vesicle with a 
 germinal spot. 
 
 Some specimens may contain a corpus luteum, which 
 has a fibrous appearance. 
 2. Utenis of cat; transverse section, logwood, C. Balsam. 
 
 L.P. shows a mucous coat containing numerous tubules, 
 and surrounded by an internal circular muscular coat 
 and an external longitudinal muscular coat ; sections of 
 numerous blood vessels may be seen. 
 
 H.P. The surface of the mucous coat has a covering 
 of (ciliated) columnar epithelium (which may not appear 
 in the section). The tvhules are iformed of (ciliated) 
 columnar cells, show a distinct lumen and take a some- 
 what irregular course towards the muscular coat, they 
 wUl therefore appear at some points in transverse 
 section. 
 
 Both muscular coats are formed of the unstriated 
 variety of muscle fibres. 
 
PREPARATION OF THE TISSUES, 
 HARDENING AGENTS, Etc. 
 
 I.-HARDENING AGENTS. 
 
 The tissues to be hardened must be removed from the 
 animal as soon after death as possible. They should be 
 divided into pieces of about J to ^ inch in size unless 
 otherwise directed, and if covered with much blood may 
 be dipped into normal saline for its removal. The volume 
 of the fluid into which they are placed should be about 
 20 to 30 times that of the tissue. 
 
 After hardening, and when required for preservation, 
 they are placed in spirit. It is best to gradually in- 
 crease the strength of the latter, placing the tissue for 
 12 hours in 40 %, for 24 hours in 60 %, and then trans- 
 fering to ordinary alcohol. 
 
 The reagents are best kept of such a percentage that 
 they may be diluted to the strength required for any 
 particular specimen. 
 
 Chromic Acid 1 %. Weigh 10 grammes of crystal- 
 lized chromic acid and dissolve in 1 litre of distilled 
 water. 
 
 Chromic Add and Spirit. This must be prepared jv^t 
 before use and allowed to cool. The usual mixture is 
 made by adding equal volumes of '5 % chromic acid and 
 spirit. It requires frequent renewal during the harden- 
 ing process. 
 
 Potassium Bichromate 2 %. Dissolve 20 grms. of po- 
 tassium bichromate in 1 litre of water. 
 
 Ammonium Bichromate 5 %. Dissolve 50 grms. of 
 ammonium bichromate in 1 litre of water. 
 
STAINING AND MOUNTINQ BEAaBNTS. 55 
 
 Mailers fluid. Dissolve 25 grma. of potassium bi- 
 chromate and 10 grms. of sodic sulphate in 1 litre of 
 water. 
 
 Osmie Add 1 %. Should be kept in a dark place or 
 in a bottle surrounded by a coating of brown-paper. 
 
 Picric Add. Place a good quantity of the crystals in 
 water for several days, shaking the bottle now and again. 
 It may be filtered from the undissolved crystals. 
 
 Ranvier's Alcohol (alcool au tiers). Mix 1 part of rec- 
 tified spirit with 2 parts of distilled water. 
 
 IL-STAINING AND MOUNTING REAGENTS. 
 
 Hcematoxylin (Kleinenberg's). 
 
 (a) Saturate some 70 % alcohol with crystallized cal- 
 cium chloride by well shaking, allow it to stand ; pour off 
 the fluid and add excess of powdered alum, again shake 
 and allow it to stand ; filter. 
 
 (6) Saturate some 70 % alcohol with powdered alum, 
 filter off the alcohol, and mix this with the first filtrate 
 in the proportion of 8 to 1. 
 
 (c) Saturate a small quantity of absolute alcohol with 
 hsBmatoxylin (which is very soluble), and add drops of 
 this solution to the mixture of {a) and (J) tUl a mode- 
 rately dark purple is obtained. 
 
 The solution may be weakened by the addition of the 
 mixture of (o) and (6) if required. Specimens must be 
 worked from alcohol to this staining fluid. 
 Logwood (slightly modified form of Rutherford's method). 
 
 Weigh 20 grms. of logwood chips, add 200 cc. of 
 water, and place in a flask. Let this stand near a fire, 
 or over a bunsen, at a temperature of about 70° C. for 
 8 hours (it must not boil). Leave in the flask for 24 
 hours, and then filter. To the filtrate add about 250 cc. 
 of '75 % alum solution till a fine purple is obtained; 
 finally add 30 to 50 oc. of spirit. The solution does not 
 
56 STAINING AND MOUNTING REAGENTS. 
 
 keep very long, but gives good results ; it must be 'fil- 
 tered each time before use, and the specimens must be 
 worked from water to the logwood solution and washed 
 in the same before mounting. 
 Carmine (Frey). 
 Place '3 grms. of carmine in 30 cc. of distilled water and 
 add drops of dilute ammonia till the carmine just 
 dissolves :. if the liquid smells strongly of ammonia leave 
 it exposed in a warm place that the excess of ammonia 
 may pass off. Add 30 grms. of glycerine and 4 grms. of 
 alcohol, and shake weU. Keep in a well stoppered bottle, 
 and dilute with water according to the strength required, 
 
 Ahim carmine. 
 
 Boil 1 grm. of carmine and 5 of alum in 100 cc. of 
 water for 20 minutes over a hot-water bath. When cold, 
 filter and boil up the filtrate with a little carbolic acid. 
 
 Picro-carmine. 
 
 Add a saturated ammoniacal solution of carmine to a 
 saturated solution of picric acid till a precipitate occurs. 
 Evaporate to one-fifth of its volume, cool, filter, and 
 evaporate the filtrate to dryness. Make a watery solu- 
 tion of the residue of about 4 % strength ; this may be 
 diluted as required. 
 
 Picric acid. 
 
 ' The saturated solution may be kept and diluted as 
 required. 
 
 Magenta (Rutherford). 
 
 For ordinary tissues the solution is made by dissolving 
 1 decigramme of magenta crystals in. 9 cc. of rectified 
 spirit, and adding 213 cc. of water. It should be kept 
 in a well-corked bottle. 
 
 Magenta for hlood (Werner). 
 
 Dissolve 1 decigramme of magenta in 15 oo. of dis- 
 tilled water, then add 5 cc. of rectified spirit and 20 cc. 
 of glycerine. 
 
 Eosin. 
 
 Dissolve '1 grm. of eosin in 100 cc. of distilled water. 
 Before mounting, the specimen may be placed, for a short 
 time, in some water acidulated with a few drops of acetic 
 acid. 
 
EPITHELIUM. 57 
 
 Aniline Blue. 
 
 Dissolve 1 grm. of aniline blue in 100 oc. of water. 
 Canada Balsam. 
 
 Place the C. Balsam in an evaporating basin and heat 
 it, at a temperature of about 70° C, from 24 to 48 hours 
 in a warm chamber, to drive off aU moisture. When 
 cold, break it up and dissolve in benzole. 
 Glycerine. 
 
 May be used as pure glycerine or diluted with an equal 
 part of water. 
 
 III.-EPITHELIUM. 
 
 Oast Skin of Newt or Frog. Clean the animal by 
 washing well, then leave 24 to 48 hours in about half 
 a pint of clean water. Eemove the oast skin, pin it 
 out on a piece of cork and place in spirit for a short 
 time to harden. 
 
 Columnar Mpithelium. Cut about 2 or 3 inches of 
 the small intestine of rabbit, rat, or frog. Pass a stream 
 of water very gently through, by means of a syringe, to 
 remove digestion products ; then do the same with fian- 
 vier's alcohol (alcool au tiers — 1 part rectified spirit to 2 
 of water). Now tie up the opposite end, inflate gently with 
 the Ranvier's alcohol, tie again at the near end and leave 
 in the alcohol for 24 hours. Cut open and place in picro- 
 carmine to stain. Gently brush the surface for speci- 
 mens. 
 
 Ciliated Epithelium. Carefully remove the trachea of 
 a rabbit or rat and treat in the manner just described. 
 There is no necessity to tie the ends so as to inflate the 
 tube. 
 
 Pigment Epithelium of JRetina is easily removed from 
 specimens of eye prepared as described on page 64, retina. 
 
 Epithelium of Bladder. Treat the bladder of a rabbit 
 or cat with Eauvier's alcohol as described above. 
 
 Cornea. Take a section of cornea of oat or rabbit, 
 hardened in 1 % potassium bichromate (page 64). 
 
58 CONNECTIVE TISSUE. — CARTILAGE. 
 
 IV.-CONNECTIVE TISSUE, 
 
 lAgamentmn N'wihoe. Bemove from the neck of an ox 
 and keep in alcohol. 
 
 Tendo AchilUs of dog or cat; keep a few days in 
 alcohol before taking sections. 
 
 Tail qf younff Bat. Keep for a few days in alcohol. 
 
 Cornea of Frog. Place it from 3 to 5 minutes in filtered 
 lemon juice, dip in '75 % salt solution, then place for 20 
 to 30 minutes in 1 % gold chloride; then for 20 to 
 24 hours in 25 % formic acid, within a dark chamber. 
 
 Tadpoles Tail. Place tadpoles for 2 days in saturated 
 picric acid; next day 30 % spirit; next day 50 % spirit, 
 then keep in spirit. 
 
 Omentum. Spread a piece on some cork and keep it 24 
 hours in spirit before use. 
 
 Lymphatic Gland. Eemove one from a dog ; make 
 several deep incisions with a sharp razor and place in 
 absolute alcohol. 
 
 V.-CARTILAGE. 
 
 Articular Cartilage. Take a piece from the articular 
 surface of a long bone softened in chromic acid (Bone, 
 page 59). 
 
 Femur of Frog. Eemove the femurs of a frog and 
 clear them from muscle, cut them across and leave in 
 saturated picric acid till soft. The acid should be 
 renewed now and again. 
 
 Costal Cartilage of dog, cat, etc. Place in ^, % 
 chromic acid for 14 or 16 days, frequently renewing the 
 fluid. Then in 30 %, 50 %, 60 %, and strong spirit. 
 
 Epiglottis of sheep ; in picric acid for 2 days, then in 
 50 % spirit till the colour is removed ; keep in spirit. 
 
 Arytenoid of sheep. Remove the cartilages with a 
 small piece of the vocal cords attached and place in 
 absolute alcohol. Picric acid may be used as for 
 epiglottis, if preferred. 
 
BONB. — M0SCLE. 59 
 
 Ligamentum Teres, for flbro-cartilage. Cut a section 
 from the head of the femur (dog) prepared as in Bone 
 (page 59). 
 
 Intervertebral cartilage, from rabbit, cat, or dog. 
 Eemove several intervertebral discs, with a small piece 
 of the bone attached ; divide into four by vertical cuts. 
 
 (1) in -05 % chromic acid for 7 days (often renew). 
 
 (2) „ -5 % „ „ 15 „ (or till soft) and 
 often renew the fluid. 
 
 (3) weak and then strong spirit. 
 
 VI.-BONE. 
 
 Long Bone. Eemove from a dog, and clear well from 
 muscle. Cut into small pieces. 
 
 (1) in "05 % chromic acid for 7 days. 
 
 (2) in '5 % chromic acid for about 12 days, till the 
 bone is soft and cuts easily. The fluids are to be often 
 renewed and shaken up. 
 
 (3) place in weak and then strong spirit. 
 
 Picric acid, in good quantity and often renewed, may 
 be used till the bone softens ; it is then placed in weak 
 and strong spirit. 
 
 Flat Bone. The frontal bone of a sheep may be 
 treated in a similar manner. 
 
 ^Young Bone. Remove from a young kitten and keep 
 in picric acid till soft : then in alcohol. 
 
 VII.-MUSCLE. 
 
 Unstriated, for teasing ; place some thin slices of un- 
 striated muscle {e.g. from small intestine) 24 hours 
 before use, in Ranvier's alcohol. 
 
 Frog's bladder. Open the abdomen and empty the frog's 
 bladder by pressure, ligature the large intestine, distend 
 the bladder by a syringe (through the anus) with Ranvier's 
 alcohol, and suspend in the same for 24 hours. The 
 epithelium can then be easily removed by brushing, and 
 the specimen stained. 
 
60 
 
 NERVOUS TISSUE. 
 
 Musetdar walls of Intestine. Cut off 2 or 3 inches of 
 the small intestine of a dog or cat. 
 
 (1) Gently clean the inside by a stream of normal 
 saline. 
 
 (2) Gently send in a stream of chromic acid and 
 spirit mixture ; tie one end, distend with the mixture 
 and then tie the other. Leave for 12 to 20 hours in 
 same mixture. 
 
 (3) Cut open the intestine and leave in renewed 
 mixture for I days. 
 
 (4) Place in 30 % spirit for 1 day and then in strong 
 spirit. 
 
 Section of striated muscle. 
 
 Place some pieces of muscle from the dog, in "5 % 
 chromic acid for 4 days. Eenew the fluid at the first 
 and third day. Place in weak then strong spirit. 
 
 Cardiac : sheep. Cut some thin slices in the direction 
 of the fibres and place in -02 % chromic acid for 24 
 hours. 
 
 VIII.-NERVOUS TISSUE. 
 
 Osmic acid preparation of medullated nerves. Take 
 'the sciatic of the frog, gently tear open the sheath and 
 place in 1 % osmic acid for two, three, or four hours. 
 
 Sections. Carefully remove a large nerve, spread over 
 a piece of flat cork and place in saturated picric acid 
 for 2 days. Eemove to dilute spirit till all the colour 
 is removed ; keep in strong spirit. 
 
 Posterior Ganglia of spinal nerves, dog or cat. Place 
 2 days in picric acid, then in weak spirit till colour 
 removed ; keep in strong spirit. 
 
 Or keep 6 days in J % chromic acid renewing at the 
 second day ; then in spirit. 
 
 Spinal Cord of ox. Cut pieces from the lumbar region 
 of about \ inch in length. Place in 1 % potassium 
 bichromate for 3 or 4 days, renewing as required. Stain 
 with carmine. This is to be prepared when required. 
 
BLOOD VESSELS. — ALIMENTARY CANAL. 61 
 
 IX.-BLOOD VESSELS. 
 
 Blood vessels. Wash out the vessels of a cat or dog 
 with a gentle stream of normal saline. Then pour in a 
 stream of 1 % potassium bichromate. Keep in the fluid 
 for 6 days, renewing now and again. Kemove to weak, 
 then strong spirit. 
 
 Fia mater. Carefully remove the pia mater from a 
 small animal and place in |- % chromic acid for 2 days ; 
 then in weak and finally in strong spirit. The head of 
 a lamb is good to work from, and the surface of the 
 brain may be removed in thin slices — the pia mater 
 attached — and then placed in the acid. 
 
 Endothelial celU, from the bladder of a frog. Tie a 
 ligature round the upper part of both hind limbs. 
 Carefully open the abdomen and place a small 
 canula, pointing towards the hind limbs, in the 
 lower part of the aorta. With a syringe very gently 
 inject some .normal saline, to remove the blood from the 
 vessels, and then remove the normal saline by a stream 
 of distilled water. Next inject a gentle stream of '5 % 
 silver nitrate, leave it in the vessels for 3 or 4 minutes, 
 and again wash out with distilled water. Inflate the 
 bladder (page 59) with water and suspend in ordinary 
 alcohol exposed to the liglit, till it turns light brown. 
 Specimens may be cut off and mounted in C. Balsam. 
 
 X.-ALIMENTART CANAL. 
 
 Tongue, of oat, dog, etc., may be kept in alcohol to 
 harden. 
 
 Salivary glands. Carefully remove the glands required, 
 make a few incisions with a razor and place in absolute 
 alcohol to harden. 
 
 Tonsils ; harden in absolute alcohol. Or place for 7 
 days in ^ % chromic acid and keep in spirit. 
 
 (Esophagus. Eemove the oesophagus and wash with 
 normal saline. Wash with a stream of the chromic acid 
 
62 LIVER, — LUNG. 
 
 and spirit mixture ; tie one end, slightly inflate and 
 suspend in the same for 24 hours. Cut across and 
 place in fresh mixture for 3 or 4 days. Place in dilute 
 and then strong spirit. 
 
 Stomach. Eemove pieces from the cardiac and pyloric 
 ends and spread over a piece of cork, after washing. 
 Place in absolute alcohol to harden. 
 
 Intestine {small and large) may be hardened in absolute 
 alcohol, as in the case of the stomach. 
 
 Or the mixture of chromic acid and spirit may be used. • 
 Wash a piece of intestine 2 or 3 inches long, distend 
 with the mixture, ligature and place in the same for 12 
 hours. Cut open and leave in same for 4 days. 
 
 XI.-LIVEE. 
 
 Liver, from pig or dog. Eemove a piece, and make 
 several cuts with the razor at distances of half an inch, 
 then place in a good quantity of 2 % potassio bichro- 
 mate for 10 to 11 days, renewing on the second and 
 fifth day. Wash, then place in weak and afterwards 
 strong spirit. 
 
 XII.-LTJNa. 
 
 Trachea of dog. Eemove and gently irrigate the 
 trachea. Distend with ^ % chromic acid and suspend in 
 the same for 2 days : cut into pieces and place in ^ % 
 for 7 days. Place in weak then strong spirit. 
 
 Lun^ of kitten. Carefully remove and distend the 
 lung with J % chromic acid and suspend in the same 
 for 18 hours ; transfer to some fresh solution and leave 
 it for 3 weeks Cut into pieces and place successively 
 in weak and then strong spirit. 
 
 Newfs lung. Distend with '5 % gold chloride, or 
 spread in the same, the lung of a freshly killed newt, 
 for 30 minutes. Keep in glycerine till required. 
 
LYMPHATIC SYSTEM. — SPLEEN. — DUCTLESS GLANDS. 63 
 
 XIII.-LTMPHATIC SYSTEM. 
 
 Lymphatic Glands. Eemove the compound lymphatic 
 gland of a dog, make an incision with a sharp razor and 
 place in absolute alcohol. 
 
 Thymus gland. Make some sharp incisions, then place 
 for 24 hours in 50 % alcohol, then in strong spirit. 
 
 XIV.-SPLEEN. 
 
 Remove the spleen from a cat, make several incisions 
 and place for 4 days in 5 % ammonium bichromate. 
 Place in weak and then in strong spirit. 
 
 XV.-THE DUCTLESS GLANDS. 
 
 Supra renal, make a deep incision and place in absolute 
 alcohol. 
 
 It may also be hardened by placing it in 2 % 
 potassium bichromate for 2 weeks if a large one {e.g. horse) 
 be used. 
 
 Thyroid; make some incisions and then place for 24 
 hours in 50 % alcohol, afterward* in spirit. 
 
 XVI.-KIDNEY. 
 
 Kidney of dog or guinea-pig. Make several deep cuts, 
 place in 2 % potassium bichromate for 2 or 3 weeks 
 (according to size) changing after the first 24 hours, and 
 as required. Keep in spirit. 
 
 Ureter of dog ; distend and keep in 1 % potassium 
 bichromate for 24 hours ; renew and keep in the same for 
 5 days, then change to spirit. 
 
 Bladder. Squeeze out the urine, gently wash out once 
 or twice with •73 % sodium chloride ; slightly distend 
 with a mixture of "5 % chromic acid and spirit (in equal 
 parts) and suspend in the same for 12 hours. Place in 
 a fresh mixture for 4 days, then remove to spirit. 
 
64 SKIN AND HAia. — EYE. — TASTE BCD8, ETO. 
 
 XVII.-SKIN AND HAIR. 
 
 After removal these may be spread on cork aud har- 
 dened in spirit. Or they may be placed in picric acid 
 for 2 or 3 days and then removed to spirit ; the latter 
 should be renewed till the picric acid ceases to stain it. 
 
 The nail is best treated with picric acid. 
 
 XVIII.-ETE. 
 
 Cornea, and junction of Cornea Iris and Sclerotic. Care- 
 fully remove the eye of a cat, divide into an anterior and 
 a posterior half. Carefully remove the crystalline lens 
 from the anterior portion ; cut the latter into two 
 parts and place for 24 hours in 1 % potassium bichro- 
 mate; renew this and leave for 14 days. Place in spirit. 
 
 Lens. Eemove the eye of a sheep, divide into an 
 anterior and a posterior half, cut carefully through the 
 cornea and remove a piece, then place the remainder in 
 MuUer's fluid for 3 weeks, renewing as required. Keep 
 in spirit. This is for sections. 
 
 Retina. Divide the eye of a pig into an anterior and 
 posterior half 5 place the latter in a mixture of equal 
 parts chromic acid "25 % and spirit for 24 hoiu's; renew 
 and leave in the same for 7 or 8 days. Place in weak 
 spirit and then in strong spirit. 
 
 Frog's retina. Place the posterior half of a frog's eye 
 for 3 or 4 hours, before required, in 1 % osmic acid. 
 
 XIX.-TASTE BUDS, etc. 
 
 Olfactory mucous membrane of guinea-pig. Eemove 
 the nasal septum and place in ^ % chromic acid for 7 
 days, changing as required. Keep in spirit. 
 
 Taste Bvds. Eemove the papillae foliata from the back 
 part of a rabbit's tongue and place in absolute alcohol, 
 Sections to be made transversely to the lines, 
 
BRAIN AND SMNAL COBD. — BBPEODDOTIVB ORGANS. 65 
 
 XX.-BRAIN AND SPINAL CORD. 
 
 Spinal cord of dog. Carefully remove the cord and 
 cut nearly through at points about J inch apart. Place 
 for 2 weeks in 5 % ammonium bichromate, changing as 
 required. Keep in weak spirit 2 days, then in strong. 
 
 Spinal cord of the ox. Divide longitudinally and 
 transversely the lumbar region, into pieces of J inch in 
 length, and place in 5 % ammonium bichromate for 16 
 to 20 days, renewing the fluid as required. Keep in 
 spirit. 
 
 Gerehrum and Cerebellum. Eemove carefully and cut 
 in thin slices, perpendicular to the surface. Place in 
 2 "5 % ammonium bichromate for 5 or 6 days; then in 
 weak spirit. Keep in strong spirit. 
 
 XXI.-REPRODUCTIVE ORGANS. 
 
 Testis of dog. Divide and place in 5 % ammonium 
 bichromate for 8 to 10 days according to size, then 
 transfer to weak spirit for 24 hours, and keep in strong 
 spirit. 
 
 Testis of rat. Place in picric acid (saturated) for 2 
 days. Keep in spirit. 
 
 Ovary of cat. Make a deep incision and place in an equal 
 mixture of '5 % chromic acid and spirit for 7 days, 
 changing as required ; then keep in spirit. 
 
 Uterus of cat. Very carefuUy inflate with the mix- 
 ture of '5 % chromic acid and spirit, and place for 24 
 hours in the same. Renew the fluid and after 3 days 
 remove to weak, then strong spirit. 
 
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