202 ?be Skin. [Book IX. 



fenfibility, occafion much uneafmefs from the friction 

 to which the iurface of the body is necefTarily ex<- 

 pofed. The epidermis confifts of a mucous fub- 

 ttance, which is fituated next the true fkin, and a dry, 

 tranfparent, and in Ibme meufure horny fubftance, 

 which is external. 



The mucous fubftance, called corpus mucofum, 

 or rere Malpighianum, is of a confidence between 

 that of a iblid and a fluid, and is often treated of by 

 anatomifts as a diftinct covering cf the body. The 

 colour of it varies according to the complexion. In 

 fair people it is white, in brown people of a dufky hue, 

 and in the Africans black. In the latter it is alfo 

 more folid, and can be feparated from the external 

 part of the epidermis, which cannot be effected in 

 Europeans. By friction, the epidermis gains very 

 much in thicknefs, as may be obferved in the hands 

 of labouring people, and in the foles of the feet of 

 thofe much accuftomed to walking, Corns, whicli 

 are nothing but hardened epidermis, are the confe- 

 quence of the prefTure and friction of tight fhoes *. 



The epidermis is not furniihed either with nerves 

 or blood-veflels, and is therefore infenfible. The 

 Abbe Fontana fubmitted fome very minute portions, 

 of -the epidermis, taken from his hand, to examina- 

 tion by a microfcope which magnified feven hundred 

 diameters. The epidermis appeared to be compofed 

 of winding cylinders, which approached each other, 

 and retreated with much regularity and order ; final! 

 globules alfo were in parts perceptible. When the 



* The care of thefe difagreeable excrefcences is very obvious 

 from this account; nothing is indeed required for this purpofe,. 

 but to cover them with any fcft adheiive iubftance, which will 

 proteft them from friction, when they will naturally decay, and. in, 

 time come off" ipontaneoufly. 



portion 



