2 per cent. solution of bichromate of potash, well washed, and strips torn off from the different coats; these can be then stained and mounted. LYMPHATIC GLANDS. The lymphatic glands of the cat are very good for examination, and should be perfectly fresh; they are best hardened in chromic acid mixture. Thin sections should be made with the microtome and stained with logwood. After washing, some of the thinnest should be placed with some water in a test tube, and shaken for half an hour or more, to detach the corpuscles from the adenoid reticulum. They must be shaken steadily or they will be knocked to pieces. Two or three sections only should be shaken at one time. They are afterwards mounted in the usual manner in Canada balsam solution. It is a good plan to inject a solution of Berlin blue. into the lymph channels of a lymphatic gland, to demonstrate the passage of lymph through it. It is done by inserting the point of a hypodermic syringe, filled with a solution of Berlin blue, through the cap. sule of a fresh gland, and slowly injecting the colouring matter; the gland is then prepared in the usual manner, and sections cut and stained with logwood. THYROID GLAND. This may be prepared in precisely the same manner as a lymphatic gland. SALIVARY GLANDS-PANCREAS. May be hardened in chromic acid mixture or in spirit mixture, and care must be taken that they are fresh and not over-hardened. Sections may be cut by the microtome or by hand and stained in logwood. TEETH. Sections of hard teeth are prepared in the same way as bone. Teeth may be decalcified by the same process as that used for bone (page 101). Good sections of teeth in situ may be made by removing the lower jaw of some small animal, as rat or mole, and decalcifying it; after the lime salts have been thoroughly washed out, it should be soaked in gum for twenty-four hours and then cut with the freezing microtome. Sections may either be mounted without staining in Canada balsam, or they may be double stained with picro-carmine and logwood. ALIMENTARY CANAL. STOMACH. The stomach may be prepared in several different ways. Ist Method. Remove and open a fresh stomach of dog, cat, or rabbit, and wash it slightly in dilute chromic acid, then place it in the ordinary chromic acid mixture and proceed as described at page 16. 2nd Method. To show the peptic cells take fresh stomach and wash quickly, then plunge into pure methylated spirit. 3rd Method. Put the stomach in Muller's fluid unwashed, for forty-eight hours. Then cut narrow strips of the mucous membrane about half an inch long by one eight of an inch wide and wash these in one-tenth per cent, osmic acid, then place them in half per cent. osmic acid from one to two hours to stain, then place them in one-sixth per cent. chromic acid and complete the hardening in the usual manner. The one-sixth per cent. chromic acid is here used without the addition of methylated spirit. Some sections of stomach should be taken from the different parts, pylorus, cardiac end, &c., and these should be stained in logwood; those which are required to show the peptic cells aniline blue. should be stained in Pyloric end of stomach with commencement of duodenum should be hardened in chromic acid mixture, or if the whole stomach has been hardened, a portion showing the junction of these two parts should be cut with the microtome and double-stained, a few sections also should be stained with logwood. Examine these sections for the gradual change in the epithelium as the one organ passes into the other. DUODENUM. May be hardened in chromic acid mixture and sections stained with logwood. Notice Brunner's glands cut in different sections, also goblet cells amongst the columnar epithelium and the fine non-striped muscle fibres running up from the muscularis mucosa to the basement membrane. ILEUM. The whole of the intestine may be hardened in chromic acid mixture or in spirit mixture (page 18), it must not be much handled and should be first slightly washed in very weak solution of chromic acid. Sections are best cut with the freezing microtome and may be stained in a great many different ways. In a section containing a portion of Peyer's glands, the treble staining process (page 57), may be used and the result will be very good, as the Peyer's glands take on the green alone, without combining another colour with it, as all the other elements in this specimen do, so that they are brought out as brilliant light green bodies. ILIO-CECAL Valve. A section should be made through the ilio-cœcal valve with a little of the intestine on either side of it, and this should be treble stained by the process mentioned at page 57. Some sections should, however, always be stained with logwood to compare with the others, as although double and treble staining differentiate the various tissues, logwood brings out the structural elements better than any other stain. SOLITARY GLANDS. Sections should be made through a piece of large intestine containing a solitary gland, and this will be well brought out by the treble staining process. LIVER. The liver may be prepared for examination in three ways : 1. By the ordinary chromic acid mixture (page 16). 2. By dilute spirit (page 18). 3. By Muller's fluid (page 17). 1. The chromic acid method. The liver must be perfectly fresh and cut into small pieces about half an inch square, these should be placed at once in the fluid without washing. A large quantity of blood will exude from them after being in the hardening |