392 CIRCULATION AND RESPIRATION 



bath for removing this accumulation is a warm bath; it should be taken 

 at night, if possible. Warm baths taken in the daytime, unless they 

 are followed by a cold shower bath, or by a dash of cold water, may 

 make one liable to colds (cf. 391). A warm bath at night also aids 

 in bringing on a good night's sleep. 



In the morning, when we wish to be aroused for the day's work, 

 especially if we must go out into the cold, a cold bath is the best. The 

 cold water gives the body a shock, in which the blood is driven inward 

 from the skin; but after a vigorous rubbing the skin glows. This is 

 due to the " reaction," as the blood re-enters the skin. 



Many persons cannot endure the shock of a tub of cold water; they 

 do not have a proper reaction, and feel chilly. Such persons can, as a 

 rule, take a cold " sponge" bath, in which the water is applied rapidly 

 with a wet sponge or washcloth. Vigorous rubbing with a dry, rough 

 towel will bring about the " reaction." 



396. Summary. The blood carries oxygen and digested food to the 

 cells, distributes the body's heat, and acts as the sewer for cell wastes. 



The organs of circulation are the heart, arteries, veins, and capil- 

 laries; also the spaces containing the lymph. 



The heart has 4 chambers, each of which can be made smaller by 

 the contraction of strong muscles. 



The right auricle receives blood from the body circulation, and forces 

 it into the right ventricle. This, in its turn, forces the blood to the 

 lungs to be oxidized. 



The left auricle receives purified blood from the lungs, and forces 

 it into the left ventricle. This forces it, through the artery called the 

 aorta, into the body circulation. 



The valves of the heart make the blood flow in one direction. 



Arteries carry blood from the heart; veins carry it to the heart; 

 capillaries carry it from arteries to veins through the body's tissues. 



Arteries have very elastic walls, and are very strong. Some veins 

 have valves that open toward the heart; the circulation in such veins 

 is helped by the pressure of muscles near them. 



The blood consists of the plasma and corpuscles. Corpuscles are 

 red, and white. Red corpuscles contain hemoglobin, which combines 



