The continued presence of albumin or of sugar in the urine indicates a 

 diseased condition of the body. 



When wastes accumulate in active tissues faster than they can be ex- 

 creted, they are diffused to other tissues and may bring about a state of 

 general fatigue. 



An excess of uric acid in the blood may be fatal. 



Efficiency in work can be increased by setting a pace that will avoid 

 fatigue through balancing metabolism and excretion. 



EXPLORATIONS AND PROJECTS 



1 To study the position and structure of vertebrate excretory organs: 

 Dissect an anesthetized frog, guinea-pig, or rat, opening it on the undersurface, 



and remove the viscera. On either side of the backbone will be found the two 

 bean-shaped kidneys. The ureters, the bladder, and the urethra may be seen in 

 their normal position. The arteries and veins leading to and from the kidneys 

 may also be readily seen. 



Cut a sheep or beef kidney lengthwise through the "pelvis". Note general 

 structure. 



2 To find the specific gravity of a sample of urine, float a hydrometer in the 

 urine placed in a tall cylinder. (Clear amber-colored fluid normally has a specific 

 gravity of about 1.02.) 



3 To determine whether urine is acid or alkaline, use litmus paper or 

 phenolphthalein or nitrazine paper. The reaction is usually slightly acid because of 

 the presence of acid sodium phosphate (NatioPOi). 



4 To test urine for sugar, use Fehling solution (see footnote 1 on page 183). 



5 To observe the effect of fatigue on muscular activity, note the change in 

 rate and speed of work as several individuals "chin" themselves as many times as 

 they can without stopping. 



QUESTIONS 



1 How do waste products originate in an organism? 



2 What waste products of metabolism are harmless to protoplasm? What 

 products are injurious? 



3 How are the waste substances of plants separated from the living parts of 

 the organism? How do animal cells dispose of wastes? 



4 In the higher animals, how is the waste removed from the many cells 

 throughout the body? 



5 In the higher animals, what specialized organs remove the wastes of 

 metabolism from the body? 



6 How is the structure of the kidney related to its function? 



7 What factors affect the composition and the concentration of the urine? 



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