SKIN, GLANDS OF. 



G75 



a 



mm. 



mffim 



Fig. 309. — Pigment Cells from 

 the skin. 



cells : as these decay, and become gradually divested of 

 their colouring-matter, they appear whitened, or " turn 

 grey." These hexagonal cells also give colour to the skin 

 of the negro, and are situated immediately beneath the 

 transparent coat. A small por- 

 tion is shown in fig. 309, the 

 vacant space denoting the situa- 

 tion of a lost hair. 



Certain parts of the skin and 

 mucous membranes are espe- 

 cially supplied with papillae, 

 which, serve as organs of touch ; 

 throughout the greater part of 

 the skin there are jmpillce more 

 or less sensitive, but only at 

 the extremities of the fingers, 

 lips, and in a few other situa- 

 tions, are these highly dev 

 loped, as in fig. 310. Papillae 

 are either filiform or tubiform, 

 and have entering into them nerves and blood-vessels ; 

 the former supplying the sensibility of the skin, and termi- 

 nating in loops, as shown in fig. 310. Pap ill a3 injected are 

 shown in Plate VII. No. 150, tongue of mouse ; villi from 

 small intestine of rat, No. 154. 



The skin is the seat of two 

 processes in particular ; one of 

 which is destined to free the 

 blood from a large quantity 

 of fluid, and the other to 

 draw off a considerable 

 amount of solid matter. 

 To effect these processes we 

 meet with two distinct classes 

 of glandulae in its substance : 

 the sudoriferous, or sweat 

 glands ; and the sebaceous, 

 or oil glands. They are both 



formed, however, upon the same simple plan, and 

 frequently be distinguished only by the nature of their 

 secreted product. The oil-glands of the skin arp 



x z 2 



Fig. 310. — A section of sTcinfrom (Ju 

 finger, showing the vascular net- 

 work of papilla, at the surface of 

 the cutis. 



can 



