OF THE HAIRS. T7 ( .) 



observed in the medulla, which contain no air, and are thence 

 pale and this is constantly the case in the lowermost part of 

 the medulla, close above the bulb. 



The medulla and the cortex are widely different if we com- 

 pare the extreme forms of their elements; in the one case we 

 have rigid homogeneous elongated plates, almost without 

 contents, in the other rounded vesicles filled with fluid or air. 

 If, however, we take into account all their conditions, we shall 

 find that the limits are not so marked, and in fact are often 

 hardly distinguishable. On the one hand, for instance, the 

 medullary cells are not unfrequently of an elongated or short 

 fusiform figure, whilst on the other the plates of the cortex 

 present a considerable cavity containing pigment. If such 

 plates contain, instead of pigment or the smaller air vesicles, 

 air in a larger cavity, as occurs sometimes though not frequently, 

 it is still more difficult to distinguish the two kinds of 

 elements from one another, and the more so if, as in red hairs, 

 the medulla and cortex are in places, or for considerable distances, 

 not distinctly defined from one another, the superficial cells 

 of the medulla being scattered and passing quite gradually into 

 the plates of the cortex, which lie very close together and con- 

 tain much air. It is not intended to imply, by this, that the 

 medulla and the cortex are identical, but only that transitions 

 exist, and that the differences which occur are less marked than 

 is commonly supposed. 



The diameter of the medulla is generally, in proportion 

 to that of the hair itself, as 1 : 3 — 5 ; relatively and absolutely, 

 it is thickest in short thick hairs, thinnest in the down and 

 hairs of the head. In a transverse section it presents a round 

 or flattened figure, and the cells which comprise it are disposed 

 in 1 — 5 or even more longitudinal series. 



[The medullary substance, the cells in which were first 

 accurately described by G. H. Meyer, varies, most of all the 

 constituents of the hair. In the down and the hairs of the 

 head, it has been stated, by some, that it is wholly absent, 

 which is to be corrected thus far, that it is certainly generally 

 absent in the former, and frequently in the latter, perhaps 

 more frequently, in certain individuals. In white hairs, even 

 those of the head, of a tolerable length and thickness, I have 



