25O APPLIED PHYSIOLOGY 



neys try to excrete the poisons, but they become overworked, producing 

 what is called Bright" 1 s disease. Then the sweat glands excrete more waste 

 matters, and in the emergency often do enough to relieve the kidneys. 



442. Relation of the skin and kidneys. The skin excretes 

 but little urea compared with the kidneys, yet its capacity for excreting 

 water is unlimited. When much water is excreted by the sweat glands, 

 only a little is excreted by the kidneys, and when little perspiration is 

 formed, the kidneys excrete more water. The amount of urea remains 

 nearly the same from day to day, and so the urine will be more colored 

 at one time than another. 



The amount of perspiration is governed principally by the tempera- 

 ture, and remains nearly the same whether much or little water is taken. 

 The amount of urine is increased by the water swallowed. A large 

 amount of water tends to wash away the urea more perfectly. Often 

 when one thinks that he has kidney trouble, an increased amount of 

 water swallowed will pass through the kidneys and bring their secre- 

 tion to a natural appearance. 



443. Excretion of poisons swallowed. When poisons have 

 been swallowed, those which pass by the liver are seized by the kid- 

 neys and excreted. Carbolic acid and turpentine are thus excreted by 

 the kidney. In passing through the kidneys these drugs may irritate 

 their cells and set up inflammation. Most drugs, whether they are 

 vegetable or mineral, pass out by the kidneys. 



444. Excretion by the liver. The liver is constantly 

 destroying all kinds of poisons, which it receives not only 

 from the blood of the intestine, but also from the rest of 

 the body. Two bile substances, glycocholic and taurocholic 

 acids, are probably formed directly from albumin; and 

 while they are excretory products, yet they are elements 

 essential to digestion. Another substance, bilirubin, con- 

 tains most of the waste coloring matter of the blood. 

 When the liver fails to excrete these substances, as in 

 jaundice, they pass out by the kidneys and color their 

 secretion yellow. 



445. Excretion by the intestine. Although the intes- 

 tine absorbs food, yet it also pours out some waste matters. 



