STRUCTURE OF HAIR. 



357 



both by the elongation of its constituent cells, and by the addition of 

 new layers of these to its base ; the apex and shaft of hair being 

 formed before the bulb, just as the crown of a tooth is before its fang. 

 The cytoblasts are round and loose at the base of the hair, but are 

 more compressed and elongated in the shaft ; and by this rectilinear 

 arrangement the hair assumes a fibrous character (see Plate XIV,, No. 

 2). Of sixteen species of the Bat tribe, the hairs of which have been 

 examined by Professor Quekett, all were analogous in structure to fig. 





fig. 169. 

 1. Hair from the Indian Bat, magnified 500 diameters. '2. Hair from the Dermestes, 

 magnified 250 diameters. 3. Hair from the Mouse, magnified 250 diameters. 4. 

 Pigment cells giving colour to the skin. 



169, No. 1 ; and the curious surfaces which these hairs present, are in 

 reality owing to the development of scales on their exterior. By sub- 

 mitting hairs to a scraping process, these minute scale-like bodies, toler- 

 ably constant as regards their size and figure, can be procured ; so that 

 Bat's hair may be fiaid to consist of a shaft invested with scales, which 

 are developed to a greater or less degree, and vary in the mode of their 

 arrangement in different species of the animal ; that part of the hair 

 nearest the bulb is nearly free from scales, but as we proceed toward 

 the apex the scaly character becomes evident. Many of the scales are 

 not unlike in shape those from the wings of butterflies, but are much 



