I 1 2 HAIRS. [SECT. 63. 



isolated, so as to be positively recognised as spindle-shaped fibres 

 with a single nucleus, so that I cannot, for the present, express 

 myself decidedly as to their nature; and the more so, as we have 

 no facts to show that contractions of the hair-follicles take place. 



The third layer is a hyaline structureless membrane, which, 

 when the hair is pulled out, always remains behind in the hair- 

 follicle, and, in connection with and also covering the papilla 

 (Dalzell), extends from its base as far as the internal root-sheath, 

 and perhaps higher. It appears, in the uninjured hair-follicle, only 

 as a very pale streak, o'ooi"' to 0*00 15'", seldom 0*002'", in thick- 

 ness, between the external root-sheath and the transverse fibrous 

 layer of the hair-follicle ; but, by preparation of an empty hair- 

 follicle, it may be easily obtained in considerable patches. It 

 then appears smooth externally, but internally presents very deli- 

 cate, transverse, often anastomosing lines, which, like the membrane 

 itself, are not altered by diluted acids or alkalies. Neither al- 

 kalies nor acids cause cells or nuclei to appear in this membrane, 

 and it belongs, accordingly, to the class of the true structureless 

 membranes. 



The papilla of the hair, less fitly termed hair-germ (pulpa pili), 

 belongs to the follicle, and represents a papilla of the cutis. It is 

 a beautiful ovate or fungiform papilla, -*-'" to -fa'" broad, jt~" to 

 Jg-'" long, and is connected by a pedicle with the conuective- 

 tissue-coat of the follicle ; it has a sharp outline, and a per- 

 fectly smooth surface ; in its structure, it harmonises completely 

 with the papillae of the cutis, and consists of an indistinctly 

 fibrous connective tissue, with scattered nuclei, and fat-granules, 

 but without cells. It contains, also, in man and in animals, 

 vessels ; but no one has as vet been able to demonstrate nerves 

 in it. 



§ 63. The root-sheath may be divided into an external and an 

 internal layer, of which the former is continuous with the epi- 

 dermis round the opening of the hair-follicle, and appears as the 

 epidermic lining of the follicle; while the internal is an entirely 

 independent layer, and enters into direct relation with the hair. 



The external root-sheath is a continuation .of the mucous layer 

 of the epidermis, invests the entire hair-follicle, and rests in 

 its lower half on the above-described structureless membrane; 

 higher up, where the latter and the transverse fibres are no longer 

 present, it lies immediately upon the longitudinal fibrous layer. 

 In structure, it corresponds entirely with the mucous layer; like 



