METABOLISM. 



469 



cleavage substances which are oxidized. Oxidation is a chemical 

 process presided over by intracellular ferments, specific in their nature, 

 as they act only upon particular chemical groups. The enzyme first 

 acts, then the resultant products undergo oxidation. 



4. DEAMIDIZATION : A liberation of the NH 2 group. 



5. SYNTHESIS : This is the combination of two or more sub- 

 stances whereby result a third, new substance. Syntheses are char- 

 acteristic of anabolism, but they do occur in catabolism. Thus, 

 with the disintegration of the tissue elements into benzoic acid and 

 glycocoll, there follows hippuric acid; urea is formed from carbonic 

 acid and ammonia. 



The energy produced by the metabolism of materials in the body 



Fig- 178a- Schematic Outline of Ventilation System in the Respiration 

 Calorimeter at Wesleyan University, Middletown, Conn. (BENEDICT.) 



can be measured by the number of calories. Heat and work represent 

 the end results of metabolism. The splendid apparatus of Atwater 

 lias accomplished calorimetric results for man hitherto unattainable. 



The end results of metabolism are thrown off by the lungs, skin, 

 intestines and kidneys. 



Foods burned within the body produce the same amount of heat 

 as when burned outside the body, according to Rubner and Atwater. 



Catabolism varies according to the age and weight of the animal ; 

 the younger and lighter the animal, the greater is the relative destruc- 

 tion of proteid. 



Peptones and albumoses have about the same caloric and nutritive 

 v*ihie as the proteid s. 



