222 



THE SKIN. 



Fi;r. 149. 



transparent homogeneous meml)rane, marked transversely on its inner 

 surface ■\viLli some raised lines, and not reaching so high as the month 

 of the follicle ; it corresponds "with the membrana propria or basement 

 membrane of analogous structures, and, like that, probably consists of 

 flattened colls. Between the two is a layer extending from the bottom 

 of the follicle as high as the entrance of the sebaceous glands, com- 

 posed of an indistinctly fibrous matrix, teariug transversely, and of 

 transversely disposed connective tissue cor])uscles, Avith oblong nuclei, 

 (fig. 149, r). This layer, which seems to be a form of connective 

 tissue, receives capillary blood-vessels. 



The ejmlcrmic coat (fig. 149, 2) of the follicle adheres closely to the 

 root of the hair, and commonly separates, in great part, from the follicle 

 and abides by the hair when the latter is ])ulled out ; hence it is some- 

 times named the " root-sheath." It consists of an outer, softer, and 

 more opaque stratum (fig. 148, ^, c ; 149, e), next to the dermic coat of 

 the follicle, and an internal more transi)arent layer (fig. 148, 1), b ; 149, 

 fg) next to the hair. The former, named also the outer root-sheath, and 



liy much the thicker of the two, corre- 

 si)onds with the mucous or Malpighian 

 layer of the epidermis in general, and 

 contains soft growing cells, including 

 pigment granules iu the coloured races, 

 which at the lower part form a much 

 thinner stratum and pass continuously into 

 those of the hair-knob ; the internal layer 

 or hmer root-sheath, represents the super- 

 ficial or horny layer of the epidermis ac- 

 cording to some authorities ; but others 

 maintain that it is not continuous with 

 that part of the skin, but ceases abruptly 

 a little below the orifices of the sebaceous 

 ducts. Lining the root-sheath internally 

 is a layer of imbricated downwardly pro- 

 jecting scales, the cuticlp of the root-sheath 

 (fig. 149, h), which is ap})lied to the 

 cortical scaly cuticle of the hair proper, 

 to whose upwardly directed scales it fits like 

 a mould. Its scales, as well as those of the 

 hair-cuticle, pass, at the bottom of the fol- 

 licle, into the round cells of the hair-knob. 

 The inner root-sheath itself consists of two 

 layers, which towards the bottom of the fol- 

 licle become blended into one (fig. 149,/^). 

 The innermost (that next the cuticula) is 

 known as Hnxleifs layer; it consists of 

 flattened polygonal nucleated cells, two or 

 even three deep. The outermost is com- 

 posed of oblong, somewhat flattened cells 

 without nuclei, in which fissures and holes 

 are liable to occur from accidental laceration, so as to give it the aspect 

 of a ]ierforated or fenestrated membrane. At the lower part both layers 

 pass into a single layer of large polygonal nucleated cells without open- 

 ings between them. 



Fig. 149. — Section op Hair 

 Follicle (Biesiadecki). 



1, Dermic coat of follicle ; 2, 

 epidermic coat or root-sheath ; a. 

 Outer layer of dermic coat, with 

 blood-vessels, h, h,c\\i across ; c, 

 middle layer ; d, inner or hyaline 

 layer ; c, outer root -sheath ; /, g, 

 inner root-sheath ; h, cuticle of 

 root-sheath ; /, hair. 



