566 DBS. GEORGE AND EEAKCES E. HOGGAK ON 



Intraepithelial Nerve-jibrils of Outer Boot-sheath. 



These nerve-fibrils, as we hare just remarked, are homologous 

 with the intraepidermic nerve-fibrils found on the general surface 

 of the body, but more especially on those parts where the epidermis 

 is thick and most quickly renewed, and upon which the desire to 

 touch is concentrated, as, for example, in the noses of most mam- 

 mals and the pulp of the fingers and toes in man (see figs. 18 & 25). 

 In the hair-follicle they are connected inferiorly with the nerve- 

 cells and circular coil of fibres, and superiorly or, rather, superfi- 

 cially with the subepidermic plexus of non-medullated nerve-fibres. 

 In many cases, indeed, they are seen to be in direct communication 

 with the intraepidermic fibrils proceeding from that plexus, more 

 especially when such an intraepidermic fibril proceeds from the 

 dermic papilla next to the hair-follicle, in which case the intra- 

 epidermic fibrils, after passing from the papilla almost perpen- 

 dicularly to the plane of the epidermis, suddenly make a turn at 

 the edge of the follicle, and, reversing completely their former 

 direction, pass downwards in the plane of the epidermic sheath 

 lining the hair-follicle (as seen in if, fig. 17, Plate XIV.), there to 

 join one or more of the nerve-cells lying upon the hair-foUicle, 

 In one important respect, however, the intraepithelial nerve- 

 fibi'ils seen within the epidermic lining of the follicle differ from 

 the intraepidermic fibrils within the epidermis on the contiguous 

 surface of the skin, inasmuch as, while the latter as a rule pass 

 directly through the epidermis at right angles to the plane of its 

 surface, the former ramify in a direction parallel to the surface 

 of the epidermic lining of the hair-follicle. The cause of this 

 difference we shall afterwards explain at greater length (see page 

 587) ; but we may shortly explain here that, in opposition to all 

 those who have hitherto written on the subject, we consider the 

 direction of growth of such fibrils to be lateral — that is to say, 

 parallel to the surface of the body. Moreover we believe their 

 presence in epidermis to be abnormal, and due to mechanical causes 

 hereafter to be explained. Once, however, they are entangled in 

 the epidermis, they are subjected to the conditions of growth of 

 that epidermis. If constant wear and consequently rapid develop- 

 ment of the epidermis is going on, the fibres are dragged rapidly 

 towards the free surface, as is seen to be the case in the free 

 epidermic surfaces of the body, where the fibrils appear almost 

 always at right angles to the plane of the surface. 



In the epidermic lining of the hair-follicle there is scarcely any 



