PORES OF THE SKIN 265 



than it originally was ; for, although it appears at 

 first to be very vascular, its vessels after a time 

 either shrink in calibre, or some of them become 

 altogether obliterated. It invariably happens that 

 when horses have had fistulae or saddle-galls, they 

 are always more disposed to subsequent injury in 

 those parts. 



THE RETE MUCOSUM. 



The third part of the skin consists of a membrane 

 which bears this name ; it is a fine, delicate, laminated 

 tissue, interposed between the cutis and the cuticle. 

 The skin takes its colour from this membrane. It 

 is from this membrane being black in the negro 

 that he takes his dark colour ; for dissection has 

 proved that his cuticle when separated from this 

 membrane is as white as that of a European. Its 

 use appears to afford protection to the delicate vessels 

 of the nerves from outward injuries. 



PORES OF THE SKIN. 



The skin exhibits an infinity of pores over its 

 entire surface, and probably the whole of these trans- 

 mit hairs. There are also numerous others, smaller 

 and less perceptible, which are called perspiratory 

 pores, from their emitting an imperceptible vapour, 

 denominated the insensible perspiration, the sensible 

 perspiration being what is ordinarily called sweat. 

 The situation of these pores is rendered manifest by 

 the condensation and collection of this exhalation. 

 But these pores can be rendered visible by macera- 

 tion, or putrefaction in the dead animal. Besides 

 these there is another set of pores, of larger dimen- 

 sions, more discernible than others in some places, 

 which are the mouths of follicles. These are of larae 



