OF THi: HAIRS. 



191 



eyebrows; and in the 24th week thev arc still absent niton the 

 hand and foot, and partly on the fore-arm and leg. 



Once formed, the hairs and hair-sacs continue to grow. 

 The former sometimes penetrate the epidermis immediately 



Fig. 74. 



Fig. 75 



(eyebrows, eyelashes, fig. 75), sometimes their points are 

 insinuated between the horny layer and the stratum Malpighii, 

 or among the elements of the horny layer itself, and grow for 

 a time covered by the epidermis (chest, abdomen, back, 

 extremities [?]), through which they eventually make their 

 passage. Involutions of the skin growing towards the hairs as 

 they pass out, never exist, and the supposition that they do, 

 rests upon a wholly subjective foundation. 



Fig. 74. Rudiment of a hair from the eyebrow (0-22'" in length), x 50, its inner 

 cells forming a distinct cone, as yet without any hair, but with the papilla indicated : 

 a, horny layer of the epidermis ; b, mucous layer ; c, outer root-sheath of the subse- 

 quent sac ; i, structureless membrane upon its outer side ; h, papilla of the hair. 



Fig. 75. A, rudimental hair from the eyebrows, with just developed but not yet 

 erupted hair, of 0-28'" in length. The inner root-sheath projects beyond the point, 

 of the hair somewhat at the upper part, and laterally at the neck of the sac ; the 

 first rudiments of the sebaceous glands appear in the form of two papillary outgrowths 

 from the outer root-sheath. B, hair-sac from the same, with its hair just erupted ; 

 the inner root-sheath projects through the aperture of the hair-sac ; the rudiments 

 of sebaceous glands are as yet not developed ; the letters a, b, c, h, i, have the same 

 signification as in fig. 74 : e, hair-bulb ; /, hair-shaft ; g, hair-point ; n, rudiments of 

 the sebaceous glands. 



