390 



THE SKIN AND ITS APPENDAGES. 



fibrils, the hair fibrils (Waldeyer, 82). Scattered between and within 

 the cells of the cortical layer are varying quantities of pigment 

 granules. The axial region of the hair is occupied by the medullary 

 substance, from 16 fj. to 20 // in diameter. This may be lacking ; but 

 if present, consists of from 2 to 4 strata of polygonal, nucleated and 

 pigmented cells. The hair shaft often contains air vesicles. 



The inner root-sheath consists of three concentric layers first, 

 of an outer single layer of clear nonnucleated cells, the so-called 



Fig. 313. Transverse section of human scalp; X I2: -dp, Musculus arrector pili ; 

 c, corium ; ep, epidermis ; fp, hair follicle ; Gap, aponeurosis ; gls, sweat-gland ; glse, seba- 

 ceous glands; KH^ club-hair; pp, papilla of hair; Re, retinacula cutis; Rp, root of hair; 

 Sp, shaft of hair; is, subcutaneous layer (Sobotta, "Atlas and Epitome of Histology"). 



layer of Henle ; second, of a thicker middle layer, made up of a 

 stratum of nucleated cells containing keratohyalin, the layer of Hux- 

 ley; and, third, of an inner cuticle, bordering upon the hair. 



The outer root-sheath is made up of elements from the stratum 

 germinativum. Here we have to do with prickle cells, surrounded 

 by an outer layer of columnar elements. The connective-tissue 

 portion of the hair follicle is composed of an outer, looser layer of 

 longitudinal fibrous bundles ; of an inner, compacter layer of circu- 



