196 OUR BODIES AND HOW WE LIVE 



than two million sweat glands in the whole body. If they 

 were laid end to end, they would stretch to a distance of 

 nearly ten miles. 



Experiment 62. Study the openings of 

 the sweat glands with the aid of a strong 

 magnifying glass. They are conveniently 

 examined on the palms. 



264. The Sweat, or Perspiration. 

 The sweat, or perspiration, is a colorless, 

 salty fluid, with a peculiar odor. It 

 is a part of the waste matter of the 

 tissues which has been filtered from 

 the blood and is got rid of through 

 these busy little glands in the skin. 



These glands are always at work 

 pouring out sweat. This may not be 

 evident to the eye or to the touch, 



because it evaporates into the air as 

 FIG. 125. BLACKBOARD 



SKETCH. fast as it is formed. In hot weather, 



Hair and Hair Follicle, or during exercise, the sweat is poured 

 A, root of hair; B, bulb out faster than it can evaporate. It 



of hair; C, internal root ft co H ects m d rops an d runs down 



shield; D, external root 



shield ; , external mem- Our f aCCS. 



cl7 fi ^"akctd mU t : The average daily quantity of per- 

 follicle; H, compound oil spiration is not far from two pints, 

 tlptVuS | but this, of course, is much increased 

 opening of hair follicle, in hot weather. It varies greatly, 

 according to what we are doing, the 



condition of health, how we are clothed, and the tempera- 

 ture of the surrounding atmosphere. 1 



1 Horses sweat all over the body, and so do human beings, but monkeys, 

 it is said, sweat only on the hands, feet, and face. In animals that perspire 



