SKIN, GLANDS OF. 



675 



Fig. 309.— Pigment Cells from 

 the skin. 



cells : as these decay, and become gradually divested of 

 their colouring-matter, they appear wliitened, or '' turn 

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

 of the negro, and are situated immediately beneath th e 

 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 papilla^, 

 which serve as organs of touch ; 

 throughout the greater part of 

 the skin there are jmpilke more 

 or less sensitive, but only at 

 the extremities of the fingers, 

 lips, and in a few other situa- 

 tions, are these highly deve- 

 loped, as in fig. 310. Papilla3 

 are either liliform 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 YIL jS'o. 150, tongue of mouse ; villi from 

 small intestine of rat, ISTo. 154. 



The skin is the seat of two 

 processes in particular ; one of 

 vrhich 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 Avitli two distinct classes 

 of glancluloe 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 can 

 frequently be distinguished only by the nature of their 

 secreted product. The oil-glands of the skin are 



X X 2 



Fig. 310. — A section of skin from the 

 finger, showing the vascular net- 

 work of papillce, at the surface of 

 the cutis. 



