Flow Till. ANIMAL 1,IVKS L'"J ( 



41t). Tlit» ditTiMMMKM' hctwt'on tlu' arttMT-lil<»<^><l 

 and veiu-blood is shown in tin- following tablr : 



VnU. Vol: 0/ 



of earhun 



f*xuorn diozid 



From ion vols, of arterial hlood may Im' oMaiiu'd . . *J0 39 



v.'iioii^ . .8 to I'J 4<) 



417. Tlio excess of oxygen in tlic arterial 

 Idooil is used up as it pas.ses throngli the eajiil- 

 laries, and is ifplaet'd hy earhon <lioxid. Th«' 

 excess of cai-hon dioxid l)roii::lit li.H-k hy llic 

 venous blood is thrown out into the air lill- 

 ing the lungs, an<l is replaced in the blood 

 by the oxygen taken up fnmi the aii'. The 

 earl)on dioxi<l is made up of one atom of car- 

 i»on obtained by the breaking up of tiic tis- 

 sues or blood elt»ments whieh contain carbon, 

 ami of two atoms of oxygen carried to such 

 tissue or element by the blood. 



418. Breathing, therefore, or the combination 

 of oxygen with carbou to form the carbon di- 

 oxid, really does not take place in the lungs, 

 hut in the various parts of the body to which 

 the bloo<l carries the oxygen. 



5c. AmoHui of air rt quired 



411>. The amount of carbon flioxid passed 

 into the blood and exhaled by the lungs is in- 

 creased by exercise, work, sunsliine and food ; 

 hence the necessity for more rapid breathintr 



