AND PHYSIOLOGY. 



311 



548. Callosities. — In many of the rodent or gnawing ani- 

 mals, the carnivora and camels, the epidermis about the joints 

 becomes very thick, making callosities or pads for the sup- 

 port and protection of the parts exposed. 



549. Epidermic Scales , — True Epidermic Scales are found 

 on the tails of many animals, such as the Beaver. 



550. Horn of Rhinoceros, — The so-called horn of the 

 Rhinoceros is nothing but a thickening of the epidermis until 

 is assumes the form of a hollow cone. 



551. Varieties of Hair. — The hairs upon the external 

 surface of mammals either present no greater irregularities 



Fig. 298. Fig. 299. 



Hair of Sable. Hair of Musk Deer. 



than do those of man, or they are slightly rough, like those 

 of the Squirrel, or knotty, as in the Bear, or furnished with 

 pointed processes, like the teeth of a saw, in other animals. 

 Some of these peculiarities are exhibited in the adjoining 

 cuts. The spines of the Porcupine and Hedgehog differ from 

 hairs only that they contain the same materials in a more con- 

 densed form. 



552. Glands of the Skin. — Cutaneous and sebaceous 

 glands are present in most mammals very abundantly. The 



54S. To which membrane of the skin do the callosities of camels, etc., belong? 549. 

 Where are epidermic scales found ? 550. What is the horn of the rhinoceros? 551. What 

 are the varieties of hair in different animals? 552. What is said of glands of the skin 



