The best staining reagents to employ are eosine and hæmatoxyline, alum carmine or borax carmine, aniline blue-black, &c. Staining methods, see Chapter [VI].
Eye.—Harden the eye of a recently killed bullock, cat, or other animal in formal (p. [23]), puncturing the sclerotic in places to allow the hardening fluid to penetrate. In about a week make a horizontal section through the eye. The anterior half (the lens having been removed) may be satisfactorily cut in gum. Sections of the crystalline lens are not very satisfactory. The best way to get specimens of the fibres is to tease a piece of the fresh lens of a fish (e.g., a cod) in a 1/40 per cent. aqueous solution of eosine. Wash the eosine off the slide with 1/2 per cent. acetic acid, and mount in Farrant’s solution.
The posterior half of the eye should be embedded in celloidin, as otherwise it is extremely difficult to get sections of the retina in its proper relation to the other coats.
Mount some specimens unstained. Stain others with the ordinary stains.
Internal ear.—Decalcifying the temporal bone of a cat, dog, guinea pig, &c., in chromic and nitric fluid. As soon as the bone is decalcified complete the hardening of the soft parts in methylated spirit, embed in celloidin, and cut sections in the longitudinal axis of the cochlea. Owing to the extreme hardness of the bone in adults it will be found best to use the petrous bone of newly born animals.
The semi-circular canals will be most readily studied in the temporal bone of fishes, or of birds, e.g., the common fowl. They also must be cut in celloidin, and stained in the ordinary way.
Nose and olfactory epithelium.—It is difficult to obtain specimens from the human subject, but very satisfactory preparations may be made from the dog, or more conveniently in a new born puppy where the bones are still cartilaginous. Harden the latter in Müller’s fluid, decalcify adult specimens in chromic and nitric fluid. Specimens of ciliated epithelium, &c., will be obtained from the lower part, and of the special olfactory epithelium from the upper part. Stain in eosine and hæmatoxyline.
Lungs.—Carefully remove the lungs of a cat without injuring the bronchi or trachea. Introduce a cannula into the trachea and gently inflate the trachea with air. Ligature the trachea and place the lung in Müller’s fluid, a weight being attached to keep the organ submerged. Harden for about six weeks, and then make sections of the various parts.
To demonstrate the endothelium of the alveoli, inject instead of air, nitrate of silver. Allow it to remain in for half an hour, then remove it by washing, and harden in Müller’s fluid.