674 THE MICROSCOPE. 



forming a wall to the bulb enclosed in its capsule. The 

 development of a hair commences at the bottom of the 

 follicle, and by the aggregation of successive cytoblasts, 

 or new cells, are gradually protruded from the follicle, 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 arrange- 

 ment the hair assumes a fibrous appearance. Of sixteen 

 species of the Bat tribe, the hairs of which were examined 

 by the late Professor Quekett, all were analogous in struc- 

 ture; and the diversity of surfaces which these bairs pre- 

 sent are in reality owing to the development of scales 

 on their exterior. By submitting hairs to a scraping pro- 

 cess, these minute scale-like bodies, tolerably constant as 

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

 Bats' hair may be said to consist of a shaft invested with 

 scales, which are developed to a greater or less degree, and 

 varying in their mode of arrangement iu the 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 those procured from the wings 

 of butterflies, but, being very much smaller, exhibit no 

 trace of striae on their surfaces ; those taken from dark- 

 coloured hairs have colouring-matter deposited on them in 

 small patches. In some cases they appear to terminate in 

 a pointed process ; in others the free margin is serrated. By 



scraping, many of them will 

 be detached separately ; but in 

 some few cases, as many as 

 four or five will be found joined 

 together : in the larger hairs, 

 the cellular structure of the 

 interior, as well as the fibrous 



Fig. 308. Transverse section of Hair character of the shaft, are 



of Pecan, showing its fibrous better seen afler the scales 



!.nd cellular structure. -l i. i 



have been removed. 

 The hair owes the greater part of its colour to x>i ( J men t- 



