SKIN, GLANDS OP. 



675 



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 papillae 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. Papillae 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 glar.dulse in its substance : 

 the sudoriferous, or sweat 

 glands ; and the sebaceous, 

 or oil glands. They are both 

 formed, however, upon the Fame simple plan, and can 

 frequently be distinguished only by the nature of their 

 iecreted product. The oil-glands of the skin an 

 x x 2 



Fig. 310. A section of skin from tlit 

 finger, showing the vascular net- 

 work of papUlce, at the surface of 

 the cutis. 



