412 TEGUMENTARY ORGANS 



to the axis of the hair, and their projecting edges give rise to the most 

 elegant sculpturings of its surface. 



The cuticle proceeds from the horny metamorphosis of the two 

 outermost layers of the pulp of the hair. The lowest portion of the 

 bulb of a hair, if viewed in section, presents a sharply defined edge 

 ^.fiS- 315-) C), which may occasionally be raised up by reagents as a 

 distinct structureless membrane ; but is normally perfectly continuous 

 with the subjacent transparent homogeneous periplast of the pulp, in 

 which lie the ordinary rounded or oval vesicular endoplasts of young 

 indifferent ^tissue. Tracing the margin of the hair upwards, we find, 

 next, that the two most superficial series of these endoplasts (D, a, b) 

 are distinguished from the rest, by being free from that deposit of 

 pigment granules which surrounds the endoplasts of the proper shaft 

 substance ; and these two series are more or less distinctly contained 

 in cavities or cells. The outer series is disposed more parallel, the 

 inner more perpendicular to the surface. Still higher, (e) the cavities 

 o f the outer series are larger, and their party walls straight and sharply 

 defined, while the endoplasts, which were at first plainly visible,, 

 disappear. In the inner series, both cavities and endoplasts disappear, 

 and the periplast seems to split up into thin parallel horny plates (e), 

 whose edges become more and more strongly marked. Such are the 

 steps in the development of the cuticular layers which may be okserved 

 in short thick human hairs, such as those of the nostril. In those of 

 the head, however, and in the hairs of the body of the calf, I have been 

 unable to trace the cuticle into anything but a structureless layer, 

 wrinkled externally, which passed into the superficial structureless 

 layer of the deepest part of the bulb (c). I formerly thought that 

 this indicated an important difference, but it is readily accounted for,, 

 if we suppose the process of development to be the same in each case, 

 the endoplasts only disappearing very early in the latter. 



The main substance of the rest of the shaft of all hairs, and its 

 entirety in some, is composed of the cortical tissue. This is a horny 

 hard substance, clear and homogeneous in white hairs, but filled with 

 pigment granules, and moreover having its own special coloration in 

 coloured hairs, which may be broken up mechanically, or by the 

 action of strong alkalies and acids, into long, pale, sometimes striated 

 fibres, which may or may not present remains of elongated endoplasts. 

 Besides the latter and the pigment granules, a multitude of striae and 

 dots are visible in the cortical substance, which are produced by 

 canals and cavities containing air. 



The cortical substance results from the metamorphosis of the 

 corresponding portion of the hair bulb. The primarily rounded 



