ANIMAL NUTRITION. C9 



througli a membraDe. The pancreatic juice of the small 

 intestines also converts albuminoids into peptones. 



Fat, liquefied by the heat of the body, is probably 

 capable of absorption without change. The digestion of 

 fat in large quantities is greatly assisted by the bile and 

 pancreatic juice. 



The absorption of the dissolved constituents of the food 

 takes place more or less in all parts of the alimentary 

 oanal, but chiefly in the small intestines. The absorbed 

 matters pass into the blood. 



The blood of an animal is the source of nourishment to 

 the whole body ; out of its ingredients all the tissues are 

 formed. The blood is also the means of conveying the 

 oxygen to the tissues which is essential to their vitality, 

 and of removing from them carbonic acid, and the other 

 products of their metamorphosis. 



3. Respiration. — The blood is supplied with oxygen 

 during its passage through the lungs, where it is brought 

 into contact with air. The oxygen is absorbed by the 

 hoemoglobin, which forms the chief constituent of the red 

 blood corpuscles. The scarlet blood thus produced is 

 ■circulated through the whole body by the arteries; the 

 oxygen it supplies is consumed in the tissues, producing, 

 .among other results, heat and mechanical work. The 

 blood finally returns from the tissues by the veins. The 

 hoemoglobin has then lost its oxygen, and has assumed a 

 purple colour ; the blood serum also contains carbonic 

 acid gas in solution, and many other products of decom- 

 position. By passing again through the lungs the carbonic 

 .acid is more or less completely discharged, and a fresh 

 supply of oxygen obtained. 



