HAIRS. 



face first, and afterwards the hairs of the eyelashes and head, which he finds in process 

 of change in infants about a year old. 



The new hairs are generated in the follicles of the old (figs, cxxi., and oxxn.). An 

 increased growth of cells takes place in the soft hair-knob, and in the adjoining part 

 of the root-sheath (the outer layer) : the growing mass pushes up the hair-knob, and 

 detaches it from its generative papilla. The newly formed mass of cells, occupying the 

 lower part of the follicle, and resting on the papilla, is gradually converted into a new 

 hair with its root-sheath, just as in the primitive process of formation in the embryo ; 

 and as the new hair lengthens and emerges from the follicle, the old one, separated 

 from its matrix by the interposition of the new growth, is gradually pushed towards 

 the opening, and at last falls out, its root-sheath having previously undergone 

 partial absorption. When a hair is pulled out, a new one grows in its place, provided 

 the follicle (from which the growth proceeds) remains entire. Heusinger, who expe- 

 rimentally studied the process in the large hairs situated on the lips of the dog, found 

 that a new hair appeared above the surface in a few days after the evulsion of the old 

 one, and attained its full size in about three weeks. 



Fig. CXXI. 



Fig. CXXII. 



Fig. CXXI. Two EYELASHES OF AN INFANT, PULLED OUT FROM THEIR FOLLICLES, 



MAGNIFIED 20 DIAMETERS (from Kolllker). 



A, the new cell-growth forming a cone, m, in the interior (as in fig. CXVIH.). In B, the 

 cone has separated into the new hair, /, g, and its inner root-sheath, b; a, outer, 

 and b, inner root-sheath of new hair ; c, pit for papilla ; d and e, the knob and stem of 

 old hair ; /, knob ; g, stem ; and A, the point of new hair ; i, sebaceous glands ; &, k, 

 sweat-glands here opening into mouth of hair-follicle. 



Fig. CXXII. EYELASH OF AN INFANT, WITH YOUNG HAIR COME FORTH, MAGNIFIED 20 

 DIAMETERS (from Kolliker). 



I, epidermis continuous with outer root-sheath ; other letters as in preceding figures. 



Distribution and arrangement. Hairs are found on all parts of the skin except the 

 palms of the hands and soles of the feet, the dorsal surface of the third phalanges of 

 the fingers and toes, the upper eyelids, the glans, and the inner surface of the prepuce. 



