RESPIRATION AND EXCRETION 393 



action of the sweat glands ; and on the other, the production by diminish- 

 ing or increasing the oxidation of the tissues." — Poster and Shore, Physi- 

 ology. 



Comparison with Cold-blooded Animals. — We have seen the bodily 

 temperature of a frog remain nearly that of the surrounding medium. 

 Fishes, all amphibious animals, and reptiles are alike in this respect. This 

 change in the bodily temperature is due to the absence of regulation by the 

 nervous system. A sort of regulation is exerted, however, by outside forces, 

 for the cold in winter causes the cold-blooded animals to become inactive. 

 Warm weather, on the other hand, stimulates them to greater activity and 

 to increased oxidation. This is naturally followed by a rise in bodily tem- 

 perature. 



Problem LIV. A final study of changes in the composition 

 of blood in various parts of the iody. {Laboratory Manual, 

 Prob. Lir.) 



Summary of Granges in Blood within the Body. — We have 

 already seen that red corpuscles in the lungs lose part of their load 

 of carbon dioxide that they have taken from the tissues, replacing 

 it with oxygen. This is accompanied by a change of color from 

 purple (in blood which is poor in oxygen) to that of bright red (in 

 richly oxygenated blood). Other changes take place in other parts 

 of the bodyi. j In the walls of the food tube, especially in the small 

 intestine, the blood receives its load of fluid food. 1 In the muscles 

 and other working tissues the blood gives up food and oxygen, 

 receiving carbon dioxide and organic waste in return. ; ) JEn the liver, 

 the blood gives up its sugar, and the worn-out red corpuscles which 

 break down are removed (as they are in the spleen) from the 

 circulation.; In glands, it gives up materials used by the gland 

 cells in their manufacture of secretions^ ' In the kidneys, it loses 

 water and nitrogenous wastes (urea). Lin the skin, it also loses 

 some waste materials, salts, and water. 



Hygiene of the Skin. — The skin as an organ of excretion is of 

 importance. It is of even greater importance as a regulator of 

 bodily temperature. The mouths of the sweat glands must not 

 be allowed to become clogged with dirt. The skin of the entire 

 body should, if possible, be bathed daily. For those who can stand 

 it, a cold sponge bath is best. Soap should he used daily on parts 

 exposed to dirt. Exercise in the open air is important to all who 

 desire a good complexion. The body should be kept at an even 



