824 NUTRITION AND HEAT REGULATION. 



the sugar.* From the above description one may conclude (Mac- 

 leod) that the sugar-regulating mechanism of the body may be 

 broken down in one of three general ways: 



1. By an accelerated production of sugar in the liver (piqure 

 reflex stimulation). 



2. By a loss of the power to metabolize the sugar on the part 

 of the tissues of the body (pancreatic diabetes diabetes mellitus). 



3. By the elimination of the sugar of the blood through the 

 kidney (phlorhizin diabetes). 



The Intermediary Metabolism of the Carbohydrate in the 

 Body. Eventually 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 is neces- 

 sary to this process (p. 804). 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. The 

 sugar is probably broken down and oxidized by the successive 

 action of a number of enzymes, with the formation, therefore, of 

 a number of intermediate products. Our knowledge at present 

 is not sufficient to warrant positive statements concerning the 

 exact nature of these intermediate processes. Two general points 

 of view have been advocated. According to some observers the 

 sugar molecule first undergoes a splitting process, and the split 

 products are subsequently acted upon by oxidases and converted 

 to carbon dioxid and water. The following steps have been sug- 

 gested, f First a cleavage to form lactic acid: 



C 6 H 12 6 = 2(Q,H 8 S ) 



Dextrose. Lactic acid. 



Then a second cleavage to form alcohol and carbon dioxid : 

 C 3 H 6 O ? = CO 2 + C,H 5 OH 



Lactic acid. Ethyl alcohol. 



The alcohol is then oxidized successively to acetic and formic acid 

 and finally to carbon dioxid and water. Others have assumed that 

 the sugar undergoes a series of oxidations, without preliminary cleav- 

 age, with the formation of such intermediate products as glycuronic 

 acid and oxalic acid, both of which are undoubtedly formed in the 

 body, since they are found in small quantities in the urine. A 



* For more complete details and the literature see Macleod, "The Metab- 

 olism of the Carbohydrates " in "Recent Advances in Physiology/' London 

 and New York, 1906, and Lusk, loc. tit.' 



t See Biichner and Meisenheimer, "Berichte d. deutsch. chem. Gesell- 

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



