794 NUTRITION AND HEAT REGULATION. 



the carbohydrate of the body is oxidized in the tissues with the 

 formation of carbon dioxid and water. Much uncertainty prevails, 

 however, as to the steps and means by which this oxidation is 

 effected. Reference has already been made to the important fact 

 that the internal secretion of the pancreas (islands of Langerhans) 

 is necessary to this process. According to Cohnheim's experiments, 

 this secretion furnishes an activating substance which enables the 

 enzymes of the muscles and other tissues to attack the sugar. While 

 the matter is still one for investigation, the trend of recent work 

 indicates that the sugar is broken down and oxidized by the suc- 

 cessive action of a number of enzymes, with the formation, there- 

 fore, of a number of intermediate products.* The first step seems 

 to be a conversion to lactic acid 



C c H 12 6 = 2C 3 H fl 3 



Sugar. Lactic acid. 



under the influence of an enzyme (lactolase or zymase). The lactic 

 acid is then split into alcohol and carbon dioxid 



C 3 H 6 3 = C0 2 + C 2 H 5 OH 



Lactic acid. Ethyl-alcohol. 



by the action of another enzyme (alcoholase or lactacidase), and 

 finally by the action of one or more oxidizing enzymes the alcohol 

 is oxidized to carbon dioxid and water. Whether or not this specific 

 process takes place in normal metabolism must be determined by 

 future work. We are certain at present only of the fact that the 

 final products are carbon dioxid and water, that is, complete 

 oxidation products, and that in some way the internal secretion 

 of the pancreas is essential to the process, either in the way indi- 

 cated above or in controlling the activity of the enzyme in the 

 liver which converts the glycogen to sugar. 



The Temporary Fate of the Carbohydrate in the Tissues. 

 The sugar absorbed from the alimentary canal may be stored in 

 the body in two forms : First, as explained above, it may be changed 

 to glycogen; or, second, it may be converted into fat and thus be 

 stored in more permanent form. Nutritive experiments, described 

 below, leave no doubt that the fat of the body may be formed from 

 carbohydrate food. It is stated that the fat that has this origin, 

 carbohydrate fat, is of a more solid consistency that is, has a larger 

 percentage of palmitin and stearin than the fat coming from other 

 sources. 



Functions of the Carbohydrate Food. The general value of 

 the carbohydrate food to the organism may be considered under 

 three heads: (1) It furnishes a source of energy for muscular 



* See Buchner and Meisenheimer, " Berichte d. deutsch. chem. Gesell- 

 schaft," 38, 620, 1905; and Stoklase, ibid., p. 664. 



