NERVES OF THE HAIRS. 



423 



pass, at the bottom of the follicle, into a layer of columnar cells which covers the 

 surface of the hair-knob. The inner root-sheath itself consists of two layers, which 

 towards the bottom of the follicle become blended into one. The innermost (that 



Fig. 483. LONGITUDINAL SECTION THROUGH THE 



FUNDUS OF A HAIR-FOLLICLE OF THE HUMAN 



SCALP. (Mertsching. ) 



a, outer, longitudinal layer of the dermic coat ; 

 I, inner, circular layer ; c, hyaline layer, which 

 seems to be formed of two layers ; d, papilla, 

 somewhat prolonged amongst the cells from which 

 the medulla is forming : this is not an uncom- 

 mon condition ; e, outer root-sheath, composed 

 near the bottom of the follicle of only two layers 

 of cells, of which the outer e' is the direct pro- 

 longation of the columnar cells, while the inner 

 e" is in contact with Heule's layer and is formed 

 of more flattened cells : both pass over the 

 papilla into the cells of the hair-bulb ; /, Henle's 

 sheath, showing nuclei only below at the level of 

 the papilla : at the bottom of the follicle it is 

 continuous with the cells of the hair-cuticle, k \ 

 g, Huxley's layer, passing round into continuity 

 with the cuticle of the root-sheath, h ; I, cells 

 which are becoming transformed into the hair-cor- 

 tex; m, medulla becoming formed from the cells 

 which immediately cap the papilla. 



next the cuticula) is known as Huxley's 

 layer; it consists of flattened polygonal 

 nucleated cells, two or three deep. The 

 outermost {Henle's layer} is composed 

 of oblong, somewhat flattened cells 

 without nuclei, between which gaps 

 frequently occur, so as to give it the 

 aspect of a perforated membrane. These 

 gaps are filled up by projections from 

 the cells of Huxley's layer. At the 

 lower part both layers pass into a single 

 stratum of large polygonal nucleated 

 cells without openings between them. 

 At the upper part also of the follicle 

 the two layers of the inner root-sheath 

 are not distinguishable from one an- 

 other (Ebner). 



The soft, bulbous enlargement of 

 the root of the growing hair is formed 



of cells which are in course of multiplication, and are not arranged in definite strata. 

 Laterally they are continuous with the cells of the outer root-sheath. Superficially 

 they are becoming gradually transformed into the horny cells of the hair and of the 

 inner root-sheath. At the bottom of the follicle they rest upon the hair-papilla, 

 which may send a delicate extension between them. The papilla, which is vascular 

 and also receives nerves, rises up into the bottom of the follicle, fitting into a cor- 

 responding excavation of the hair-knob. In the large tactile hairs of animals it is 

 very conspicuous. As the follicle, in short, is a recess of the corium, so the hair- 

 papilla is a cutaneous papilla rising up in the bottom of it. 



Nerves of the hairs. Nervous branches pass to the hair-follicles, and some, 

 as just remarked, enter the papilla ; but besides these, many fibres pass into the 

 outer root-sheath, where they appear to end as in the Malpighian layer of the 



