908 NUTRITION AND HEAT REGULATION. 



not only as above described from dextrose, but also from proteins 

 through deaminization of the amino-acids. 



CH 3 CHNH 2 COOH + H 2 O = NH 3 + CH 3 CHOHCOOH 



Alanin. Lactic acid. 



The lactic acid from either source may be resynthesized to 

 sugar by a reversal of the reactions indicated above, or it may be 

 further broken down and finally oxidized to carbon dioxid and 

 water. A possible series of stages in this last process is indicated 

 in the following reactions : * 



CH 3 CHOHCOOH H 2 = CH 3 COCOOH 



Lactic acid. Pyruvic acid. 



CH 3 COCOOH C0 2 = CH 3 COH 



Pyruvic acid. Acetic aldehyde. 



CH 3 COH + O = CH 3 COOH 



Acetic aldehyde. Acetic acid. 



CH 3 COOH + 4O = 2H 2 O + 2CO 2 



Acetic acid. 



Most of the abundant amount of carbohydrate taken in our daily 

 diet undergoes no doubt this final oxidation and yields up its avail- 

 able energy for the most part in the form of heat, although in part 

 it may be used in muscular work or in other ways for example, in 

 synthetic processes. The details referred to above are at present 

 uncertain. The steps that may be considered as established are 

 represented by the series: 



Glycogen - Dextrose -> Lactic acid -> Carbon dioxid and water. 



This whole breaking-down process is frequently referred to under 

 the designation of glycolysis. We must believe that the series of 

 changes designated under this name involve the operations of a 

 number of different enzymes, and, as has been described previously 

 (p. 888), the internal secretion of the pancreas takes some essential 

 part. 



At least one other interesting product formed from sugar 

 has been detected in the body, namely, glycuronic acid. This 

 substance has been obtained from the blood, liver, and urine, and 

 exists usually combined with various toxic or injurious substances, 

 such as the phenols or camphor. When these substances are 

 given to animals or, as in the case of the phenol, are formed in the 

 body, they are apparently conjugated with glycuronic acid and 



* See Neuberg, "Biochemische Zeitschrift," 53, 406, 1913. 



