THE SKIN. 291 



the hair like a sheath. In the thick hairs of the beard the 

 sheath consists of three rows of cells the external row, after- 

 ward forming Henle's sheath, and the two inner rows of cells, 

 the sheath of Huxley. In finer hairs there are only two layers of 

 such cells. These corpuscles are originally similar in structure, 

 having a very granular appearance and an indistinct nucleus. 

 The sheath is thinnest where the hair-papilla is broadest. 

 The cells of the external layer (Henle's) become paler and lose 

 their nuclei earlier than those of the inner layer, so that on a 

 level with the upper part of the papilla there is a marked dif- 

 ference in the appearance of the two layers of cells. Formerly 

 it was supposed (Biesiadecki) that Henle's sheath commenced 

 at this point and was a product of the external root-sheath, 

 corresponding in this respect with the corneous layer of the 

 epidermis. The cells of Huxley's layer afterward become 

 transparent also and lose their nuclei, and can then no longer 

 be distinguished from the cells of Henle's layer. The internal 

 root-sheath is now formed of transparent, non-nucleated, spin- 

 dle-shaped, or flattened bodies which surround the hair-cutl- 

 cula as far as the neck of the hair- follicle. 



Within the internal root-sheath lies the liair proper, which 

 consists of a knobbed extremity, the root of the hair, and a 

 cylindrical portion, the shaft. Between the hair proper and 

 Huxley's layer lies the hair-cuticula. This latter consists of 

 two rows of cells an external one, closely united with Hux- 

 ley's layer, and an internal one, united to the hair-shaft. They 

 both arise from the cylindrical cells seated directly upon the 

 upper part of the neck of the papilla to the inside of the cells 

 producing the internal root-sheath. The cells of the inner 

 cuticula (the hair-cuticula) are at first round, then cuboid in 

 form, and finally, long and prismatic. Above the papilla they 

 are more elongated, and commence to overlap the cells above 

 them, With the flattening out of the cells they assume the 

 form of rhomboid or ovoid plates, so that above the free sur- 

 face of the skin one cell partly covers the bodies of four or five 

 others. At first they lie perpendicularly to the long axis of the 

 hair, but afterward they are parallel with it. Above the papilla 

 they form spiral rows around the hair shaft, so that in any sec- 

 tion of this part the cells appear of a long cylindrical or spin- 

 dle-shape. The external or root-sheath cuticula consists at 

 first of round cells which afterward flatten and lie in the same 



