6o PRACTICAL HISTOLOGY. 



ALIMENTARY CANAL, AND THE GLANDS 

 CONNECTED WITH IT. 



THE LIPS. 



PREPARATION. Place small pieces of the lips of a dog or cat in chromic acid and spirit 

 mixture for two weeks, and, when they are hardened, make vertical sections of them in the 

 ordinary way. Stain a section with picrocarmine, and mount it in Farrant's solution. 



EXAMINATION (L). Observe the hair-follicles on the outer surface of the lip, and the 

 inner surface covered by stratified squamous epithelium, and if the animal's skin was pigmented 

 the deeper layers of the epithelium contain black pigment or melanin. Between these two 

 surfaces observe the transverse sections of the orbicularis oris muscle, its muscular bundles 

 surrounded by connective tissue, continuous with the connective tissue of the rest of the lip. 

 All the connective tissue is red, the glands and muscle yellowish, and their nuclei deep red. 

 Numerous sections of blood-vessels and nerves are seen. (H). Place the stratified epithelium 

 in the field of the microscope and examine it. Observe the epithelium, and study particularly 

 the prickle-cells and the pigment in the cells of the deeper layers. The various layers of a 

 hair-follicle are easily made out, and the sebaceous glands opening into them are easily 

 studied (compare hair-follicles, p. 93). 



TONGUE. 



The muscular substance of the tongue is enclosed in a mucous membrane, covered with 

 stratified epithelium. The mucous membrane on the back and sides of the tongue is provided 

 with papillae filiform, fungiform, and circumvalate and on these are small secondary papilla?. 

 There is a thin sub-mucous layer, whose connective tissue is continuous with that surrounding 

 the muscular substance. The muscular substance consists of longitudinal, transverse, and 

 vertical bundles of striated muscle. In the posterior part of the dorsum of the tongue are to 

 be found mucous and serous glands and adenoid tissue, and on the sides of the tongue the 

 papillas foliatse, in which lie the taste-bulbs. 



PREPARATION. Harden the tongue of a cat,and also a partof the human tongue, in chromic 

 acid and spirit mixture for two weeks, and make transverse sections. Stain one with logwood 

 and mount it in dammar, and stain another with picrocarmine and mount it in Farrant's solution. 



EXAMINATION (L). Observe the papillae, confined to the dorsum of the tongue, beset 

 with secondary papillae, and covered with epithelium ; beneath these the scanty sub-mucous 

 coat, containing sections of blood-vessels. In the middle of the muscular substance a verti- 

 cally placed septum, and muscular fibres running transversely out from it. Observe muscular 



