288 



MANUAL OF HISTOLOGY. 



forearm, thigh, arm, shoulder, forehead, abdominal wall, ax- 

 illa, fore-leg, face, volar and dorsal surfaces of the hands and 



feet (Neumann). They are less 

 developed on the flexor than on 

 the extensor surfaces. 



The size of the individual mus- 

 cles varies according to the person 

 and the region of the body. It is 

 impossible, therefore, to recognize 

 with certainty a slight hypertro- 

 phy or atrophy of these structures. 

 For information as to their 

 blood, lymph, and nerve supply 

 see the article on unstriped muscle. 

 The hair. The parts to be 

 studied in connection with the hair 

 proper are the hair-follicle and 

 the hair-papilla. Th e hair proper 

 is a cylindrical structure seated 

 within the hair-follicle and upon 

 the hair-papilla. Its base lies 

 embedded either in the subcuta- 

 neous connective tissue or in the 

 corium. The portion of the hair 

 proper within the follicle is called 

 the root of the hair, and the re- 

 mainder the shaft of the hair. 

 The true hair-follicle includes all 

 that part of the hair-sac below 

 the place where the sebaceous 

 duct enters the hair-follicle. It 

 is of very variable size and con- 

 sists of a blind extremity and a 

 funnel-shaped orifice (a). The 

 follicle is narrowed just below 

 this funnel-shaped orifice and 

 forms the so-called neck of the 

 hair-follicle (b). This is the nar- 

 rowest part of the follicle, and 

 is the place where the duct of the sebaceous gland enters. 

 From the neck downward the hair-follicle increases in size, be- 



Pio. 122. Hair from beard: a, canal of 

 exit ; 6, neck of hair-follicle ; c. lower part of 

 hair-follicle : d. external sheath of hair-folli- 

 cle ; , internal sheath of hair-follicle : /. ex- 

 ternal root-t-heath of hair; g, internal root- 

 Bheath of hair ; A, cortical substance ; t, me- 

 dulla of hair ; I, root of hair ; m, fat-cells ; n, 

 arector pili ; o, papilla of skin ; p, papilla of 

 hair ; i, rete mucosum : t, sebaceous gland ; 

 ep, stratum cornenm, which is continued into 

 the follicle. UicRiadcckl. 



