GLANDS AND PORES OF THE SKIN. 409 



having a little tube, or pore, proceeding from it, passing out 

 through the rete mucosum and cuticle, and ending on the sur- 

 face of the animal with an open mouth. As before remarked, 

 there are three kinds of these glands and pores. 



The sweat-glands and pores, of which the skin of the horse 

 will present many millions, throw off by far the greater part 

 of the worn-out particles of matter of the animal body. The 

 worn-out matter is separated from the blood by the sweat- 

 gland, and passes off through the sweat-tubes in the form of 

 vapor, called insensible perspiration. 



The pores of the skin have the power of becoming larger and 

 smgkller, as circumstances require. Heat or vigorous exer- 

 cise causes them to open, for then a very rapid waste of the 

 system takes place. If, when in a state of active perspiration, 

 from whatever cause, the animal becomes suddenly cooled, the 

 pores of the skin will close up, and the worn-out matter, no 

 longer being able to pass off through the skin, seeks an outlet 

 in some other way. It is thrown on the lungs, bowels, or 

 kidneys, and the consequence is pneumonia, pleurisy, cold, in- 

 flammation of the bowels, kidneys, etc. 



The Oil-glands and Oil-jwres. — The oil-glands are situated 

 in the true skin. They are not so numerous as the sweat- 

 glands, and are much more numerous in some parts of the 

 body than in others. Each gland has a little tube, duct, or 

 pipe leading from it, and terminating in the open mouth, or 

 pore. Most of the oil-pores open on the surface of the ani- 

 mal ; but some of them open into the sheath of the hair, sup- 

 plying it with a hair-oil of nature's own manufacture. 



The purpose of this oil is to keep the skin in its naturally 

 soft, pliant, and elastic condition — to protect it from the irrita- 

 tion which the wind and rain and the sweat and vapor, thrown 

 off by the sweat-pores, would produce. Being an oil, it cools 

 slowly, and is a great protection against the chilling of the 

 hide by cold. 



Around the border of the eyelids it serves to keep the tears 



