570 



THE SKIN. 



pigment found both within and between the scales, which, in 

 addition, hold a diffuse coloring matter, especially in red hair. 

 Gray and blonde hair are without pigment granules. After being 

 pulled out the hair shows minute air-bubbles in its substance j 

 but there is no foundation* whatever for the belief that the gray 

 color of the hair is due to the presence of such air-bubbles. The 

 original hue of the hair is caused by the pigment stored up in its 

 medullary and horny portion, and corresponds to the amount of 

 coloring matter present in the rete mucosum of the skin, as 

 seen in leukopathia, vitiligo, and in variegated or pied animals. 

 Unquestionably, the amount of pigment is closely connected with 



FIG. 237. POUCH OF THE HAIR FROM THE SCALP OF MAN. 

 TRANSVERSE SECTION. 



-E, root of the hair ; C, cuticle ; IS, inner root-sheath ; #2, cuticular layer between the 

 two root-sheaths ; OS, outer root-sheath ; S l , hyaline basement-layer between outer root- 

 sheath and follicle; F, follicle. Magnified 500 diameters. 



the general nutrition of the skin and under the control of the 

 so-called trophic nerves, as proved by the rapid turning gray 

 of the hair in exhaustive diseases and after mental emotions. 

 The shape of the hair is best studied in transverse sections. Flat 

 hair exhibits, as a rule, a circular or oblong section, while in 

 curled hair this is elliptical or uniform. (See Fig. 237.) 



Shedding of the Hair. We know through A. Kolliker and 



