ANIMAL PHYSIOLOGY. 



[LESSON 27. 



FIG. 150. 



a totally different aspect ; here the cortical substance is restricted 

 to a narrow ring, which forms the periphery of the circumference 



all within it consists of me- 

 dullary cells (Fig. 152). 



It is easy to understand 

 how the Indians can use these 

 quills in such varied pattern ; 

 they have no support, and can 

 be flattened with the greatest 

 ease. In the two last illus- 

 trations the cuticle ceases to 

 be present, and cannot there- 

 fore be shown. 



460. Since we quitted the 

 examination of human hair and 



wool, we have lost all trace of 

 Transverse section, quill of English Hedgehog. ^ external imbrications> - and 



it might be inferred that these characteristics are confined to man, 

 and the sheep ; but this is by no means true, for, on the contrary, 

 many animals there are in which this particular arrangement is shown 

 in great perfection. 



461. Thus, the hair of the seal (Phoca vitulina) presents them in 



Fro. 151. 



FIG. 152. 



Longitudinal section, quill of 

 English Hedgehog. 



Transverse section, quill of American 

 Porcupine. 



a manner more nearly resembling a vegetable stem than any thing 

 animal (Fig. 153). 



462. The hair taken from the belly of the mouse (Mus muscu- 

 lus) is very interesting (Fig. 154). The imbrications are well shown, 

 but its beauty consists in its cellular medulla ; some cells are nearly 

 white, others are intensely black ; in some parts of its structure the 



