230 GENERAL ANATOMY. 



particular in the skin having been marked; at others, produc- 

 tions of this kind exist on almost every part of the skin, con- 

 stituting a species of ichthyosis. 



The warts of the skin and those of the mucous membrane, 

 may be approximated to the accidental horny productions, and 

 be considered as an imperfect horny tissue, both of them par- 

 ticipating in the horny tissue, and in that of the membrane. 



In certain general as well as local affections of the skin, as 

 well as the habitual contact of acids, &c. as happens in some 

 professions, the nails soften, become fleshy, and imperfect 

 horny tissue, vegetate irregularly, present excrescences, be- 

 come dry, and fragile. They always partake of the healthy 

 or diseased state of the skin of which they are a production. 

 Inverted toe nail is merely the mechanical cause of an inflam- 

 mation of the skin. 



II. OF THE HAIRS.* 



335. Hairs, pili 9 crines, are horny filaments, generally 

 fine and long, which in a greater or less number cover almost 

 all parts of the skin, except the palm of the hand and the sole 

 of the foot. 



Each hair consists of a bulb and stem, and the texture of 

 each of these parts is tolerably complex, particularly distin- 

 guishable in their most voluminous points. 



336. The bulb or follicle of a hair, which Malpighi com- 

 pared to the vases in which gardeners plant vegetables, and 

 which has been ably described by Chirac, is situated in the 

 thickness of the dermis or under it; it is of an ovoid form; by 

 one of its extremities, which penetrates obliquely through the 

 skin, it communicates with the surface of that membrane; and 



* P. Chirac, Leitre tcriie a M. Regis sur la structure des cheveux. Mont- 

 pellier, 1688. M. Malpig-hi, de Pills, ols. in op. posth. WithofF, JLnatome. 

 pili humani. Duisb. 1750 et in Comm. soc. sclent. Getting 1 . 1753. ,T. H. 

 Kniphof de pibrum usu. Erf. 1754. Duverney, (Euvres anatom. Paris, 

 1761. Albinus, Acad, annot. lib. iv. chap. ix. T. P. PfafF, de variet. pilor. 

 natural et prseternat. Halae, 1796. Car. Asm. Rudolphi, Diss. depilorum 

 structura, Gryphiswald, 1806. Gautier, L. c. Heusinger, L, c. &c. 



