REGENERATION OF HAIR. 



225 



to tlie hair (fig-. 152, d). is soon distingnislied by its transliicency from the more 

 opaque outer jiart that fills up the rest of the cavity. The young hair continuing- 

 to grow, at last perforates the cuticle (fig. 152, C. ff), either directly or after fii-st 

 slanting up for some way between the mucous and homy strata : it is often, 

 bent like a whip, and then the doubled part protrudes. 



The fii'st hairs produced constitute the lanvgo ; their eruption takes place 

 about the fifth month of intra-uterine life, but part of them are shed before 

 birth, and are found floating in the liquor amnii. Kolliker affirms that the 

 infantile hairs are entu-ely shed and renewed within a few months after birth ; 

 those of the general sm-face first, and afterwards the hairs of the eyelashes and 

 head, which he finds in process of change in infants about a year old. 



Eeg-eneration. — The new hairs are generated in the follicles of the old (figs. 153 

 and 154). An increased growth of cells takes place in the soft hair-knob, and in. 



Fiff. 153. 



Fig. 154. 



Fig. 153. — Two Eyelashes op an Infant, pullei) out from their Follicles, 

 MAGNIFIED 20 DiAMETERs (Koiliker). 



A, the new cell-growth forming a cone, m, in the interior (as in fig. 152, a). In B, the 

 cone has separated into the new hair, /, (j, and its inner root-sheath, 6 ; a, outer, and 

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

 hair ; /, knob ; fj, stem ; and /(, tlie point of new hair ; i, sebaceous glands ; k, k, sweat- 

 glands here opening into mouth of hair-follicle. 



Fig. 154.— Eyelash of an Infant, with Young Hair come forth, magnified 20 



Diameters (Kolliker). 



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



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-fonned mass 



of cells occupying the lower part of the follicle, and resting on the papiUa, is 



gi-adually converted into a new hair with its root-sheath, just as in the primitive 



process of fomation 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 



VOL. II. ^ 



