236 GENERAL ANATOMY. 



As to those of the wens of the eye-brow, of the cranium, &c. 

 they appear to me to be nothing more than sebaceous folli- 

 cles, and the hairs they contain, than hairs of the skin, which 

 instead of being directed to the surface of that membrane 

 through the orifice of the follicle, have been turned aside by 

 the accidental enlargement of that cavity. 



345. These alterations of the hairs* like those of the nails, 

 have all their origin and cause in the generating parts; the horny 

 part produced, suffers its effects. When a hair has been torn out 

 by violence or has fallen by the effect of a disease of the skin, 

 and this has ceased, it grows again and increases by the same 

 organic process as the nails. This regeneration is effected 

 in the same way as in the first production [343.] When from 

 age or other causes, the hairs begin to whiten, it is by its free 

 extremity the albinism begins; the autumnal whitening of 

 many animals takes place in a similar mode, which seems de- 

 cisively to indicate, that the interior of the hair is the seat of 

 a sort of imbibition, the matter of which is furnished by the 

 papillae of the bulb or follicle. This would also seem to be 

 indicated by the circumstance, that after severe fevers, and in 

 many chronic diseases, the hairs of the head, when they do 

 not fall, undergo a kind of diminution or atrophy; they be- 

 come transparent, dry and brittle, and when health is restored, 

 resume their original qualities. The hair of the head has also 

 been seen, after or without experiencing the change produced 

 by albinism, to change colour and become black. The mor- 

 bid phenomenon of the plica polonica, in which the hair is 

 said to become soft and fleshy, and to bleed when cut close to 

 the skin, forms no exception to the general proposition, that 

 the stem of the hair only participates in the healthy or morbid 

 state of the skin. It may, in fact, easily be conceded, that 

 the papillae of the hair, if it is inflamed, may rise, contained 

 within the root of the hair to the level of the skin, and that 

 its vascular tissue may be wounded in cutting the stem of the 

 hair, but there is not much exaggeration in what is related con- 

 cerning this affection. 



* Plenck, de Morbis capillorum, in op. tit. W. Weclenmcycr, Hisioria 

 pathol. pilorum. Getting. 1812, 4to. 



