THE PERSPIRATION. 273 



glands is a transparent colorless liquid, with a peculiar odor, 

 varying in different races, and in the same individual in 

 different regions of the body. Its quantity in twenty-four 

 hours is subject to great variations, but usually lies between 

 10,850 and 31,000 grains (or 25 and 71 ounces). The 

 amount is influenced mainly by the surrounding tempera- 

 ture, being greater when this is high; but _ it is also in- 

 creased by other things tending to raise the temperature 

 of the body, as muscular exercise.* The sweat may or 

 may not evaporate as fast as it is secreted; in the former 

 case it is known as insensible, in the latter as sensible per- 

 spiration. By far the most-passes off in the insensible form, 

 drops of sweat only accumulating when the secretion is very 

 profuse, or the surrounding atmosphere is so humid that it 

 does not readily take up more moisture. The perspiration 

 in 1000 partsx contains 990 of water to 10 of solids. Among 

 the latter is, in health, a little urea, some sodium chloride, 

 and otheivsalts. In diseased conditions of the kidneys the 

 urea may be greatly increased, the skin supplementing to a 

 certain extent deficiencies of those organs. 



The Sebaceous Glands nearly always open into hair fol- 

 licles. They are small compound racemose glands (p. 131). 

 Each presents a duct, opening near the mouth of the hair 

 follicle; when followed back this duct is found to divide 

 into several branches which end in globular expansions. 



Describe the perspiration. How much is secreted daily? Point 

 out conditions influencing its amount. What is meant by " insensi- 

 ble perspiration"? Under what conditions do we find "sensible 

 perspiration"? What percentage of solids exists in the sweat? 

 What do they contain? When is the proportion, of urea in the 

 perspiration apt to be increased? 



Where do the sebaceous glands open? To what type of gland do 

 they belong? 



* In fever the sweat glands are paralyzed, and we find a high temperature 

 of the body with a dry skin. 



