RESPIRATION 



385 



Changes in the Blood within the Lungs. — Blood, after leaving 

 the lungs, is much brighter red than just before entering them. 

 The change in color is due to a taking up of oxygen by the htcmo- 

 globin of the red corpuscle. Changes taking place in blood are 

 obviously the reverse of those which take place in air in the lungs. 

 Blood in the capillaries within the lungs gains from four to five 

 per cent of oxygen which the air loses. At the same time blood loses 

 the four per cent of carbon dioxide which the air gains. The water 

 given off is mostly lost from the blood. 



Tissue Respiration. — It has been found, in the case of ver>' 

 , simple animals, such as the amoeba, that when oxidation takes place 

 in a cell, work or release of heat results from this oxidation. The 

 oxygen taken into the lungs 

 is not used there, but is car- 

 ried by the blood to such 

 parts of the body as need 

 oxygen to oxidize food mate- 

 rials either in the performance 

 of work or the maintenance 

 of the body temperature. 

 The quantity of oxygen used 

 by the body is nearly depend- 

 ent on the amount of work 

 performed. From twenty to twenty-five ounces is taken in and 

 used by the body every day. Oxygen is constantly taken from 

 the blood by tissues in a state of rest. This ox3^gen is used up 

 when the body is at work. This is proved by the fact that in a 

 given time a man, when working, gives off more carbon dioxide 

 than the oxygen he has taken in during that time. 



'^Alcohol interferes with the Respiration of the Cells. — Alcohol 

 is quickly absorbed from the stomach and intestine and as quickly 

 disappears. After it is taken, little or no alcohol, or any substance 

 like alcohol, or any substance containing so little oxygen as alcohol, 

 can be found in any waste of the body. Hence the inference is 

 that it must be oxidized, although the exact point and the manner 

 of its oxidation may not be known. But the evidence for its oxi- 

 dation is the same as that for the oxidation of sugar. 



hunter's BIOL. — 25 



Diagram to show the respiration of cells. 



