138 



DIGESTION 



sleeping ; since in that state the stomach, as well as the -brain 

 and the muscles, seeks release from labor. (Eead Notes 12 and 13.) 

 45. The Kidneys. Besides those already described, the 

 abdominal cavity contains other important organs, viz., the 

 kidneys and spleen. The kidneys are two in number, located in 



the loins behind the intestines, one 

 on each side of the spinal column. 

 They are shaped like a bean, being 

 about four inches long, two inches 

 wide, and one inch thick. The func- 

 tion of the kidneys is to purify the 

 blood by removing from it a poison- 

 ous substance called urea and cer- 

 tain waste products. If their action 

 is in any way interfered- with, blood- 

 poisoning takes place, on account 

 of the accumulation of urea, and 

 effete materials in the system, pro- 

 ducing coma, which rapidly proves 

 fatal unless it is relieved. The 

 watery fluid secreted by the kid- 

 neys is carried by two tubes, called 



FIG. 32. THE KIDNEYS AND 

 BLADDER 



ureters, to the bladder. 



12. Work of Exertion. "The best time to make great exertion is 

 about two hours after a meal. It is not a good time before breakfast, 

 although moderate work may be then performed ; and those who go to 

 work before breakfast should first take a cup of hot milk, tea, or coffee, 

 or other simple food. The body is weakest before breakfast. 



"Violent or rapid exertion made by children, and also by stout and 

 aged people, often injures, and sometimes causes disease of the heart, 

 when the same taken in the ordinary way would do no harm. Rapidly 

 running upstairs, or to meet a train, sometimes causes death. Hence, 

 while exercise is of the utmost importance to health, it should be taken 

 in a regulated and rational manner, and particularly by those who have 

 passed the period of youth. But disease of the heart, even in youth, may 

 often be traced to indiscretion in this particular, whether in rowing, run- 

 ning, or jumping." Edward Smith on Health. 



13. Tight Clothing interferes with Digestion. " On one wet winter's 

 day at Florence, some years ago, I had been spending the morning in the 



45. What are the kidneys and their functions ? 



