IO8 APPLIED PHYSIOLOGY 



body. The hair should be washed as often as it becomes 

 dirty. 



202. Perspiratory glands. In almost every part of the 

 skin there are little tubes made of cells of epithelium, like 

 those of the epidermis. Their lower ends are coiled into 

 a knot, and their outer ends open upon the surface of the 

 epidermis. Each tube is a perspiratory gland. The cells 

 of each gland make the sweat or perspiration. The 

 perspiration is being given off all the time, and dries as 

 fast as it forms. But if we are too warm, it is given off in 

 such amounts that it collects in drops. About a quart is 



! produced every day, and much more on a hot day. 



203. The perspiration. The perspiration is nearly all 

 water. A little mineral matter and some oxidized waste 

 matter are dissolved in it. You have already learned that 

 the perspiration takes away the extra heat when we are 

 too warm. This is the main use of the perspiration. It 



\ also takes away some waste matters of the body. 



204. The waste of the body. We will now study how 

 these waste matters are given off. All oxidation within 

 the body produces carbonic acid gas and water. The car- 

 bonic acid gas is of no use in the body, but passes off as 

 waste through the lungs. A great deal of water must pass 

 off from the body, so as to wash away the waste matter. 

 Water is found in everything which the body gives off. 



The oxidation of albumin produces, in addition to the 

 water and carbonic acid gas, another substance which we 

 call urea. Urea is a poisonous waste substance, and must 

 be removed as fast as it is formed. If oxidation is incom- 

 plete from lack of oxygen or other causes, other substances 

 like urea are formed. Many of these substances are ex- 

 tremely poisonous. Urea and all substances like it are 

 given off by the perspiratory glands, and also by another 



