Chemical Changes in Animal Organism. 317 



brought about in the animal body. It has been shown, for 

 example, that a liver rich in glycogen gives rise on perfu- 

 sion to appreciable quantities of lactic acid. In this reaction 

 the glycogen is first hydrolyzed so as to yield dextrose. 

 Conversely, also, lactic acid, when administered to a normal 

 animal, gives rise to glycogen, and when given to a diabetic 

 subject causes an increased output of dextrose in the urine. 

 It has been suggested that the conversion of dextrose into 

 lactic acid takes place through the following stages : 



(1) CH 2 (OH)-(CH(OH))].CHO - 2CH 2 (OH)-CH (OH) CHO 



Glyceric Aldehyde. 



(2) CH 2 (OH)-CH(OH) CHO * CH 3 CO-CHO 



Pyruvic Aldehyde. 



(3) CH 3 CO-CHO CH 3 CH(OH)-COOH 



Lactic Acid. 



It is also possible that the isomeride of glyceric aldehyde, 

 namely, dihydroxy acetone, CH 2 (OH)-CO-CH 2 -(OH), is 

 formed in the first stage of the reaction. The question 

 arises then as to which of these possible intermediary pro- 

 ducts (if any) is formed when dextrose is converted by yeast 

 into ethyl alcohol. Lactic acid is a possible intermediary 

 product, for on treatment with sulphuric acid it can be 

 converted into a mixture of formic acid and acetaldehyde 

 CH 3 -CH(OH).COOH = CH 3 CHO + H COOH; 



and acetaldehyde on reduction yields ethyl alcohol. Acet- 

 aldehyde can also be derived from pyruvic aldehyde, which 

 on oxidation yields pyruvic acid, CH 3 -CO-COOH, from 

 which by scission of carbon dioxide acetaldehyde is formed, 

 and Neuberg has actually shown that this reaction takes 

 place in the presence of yeast. Numerous investigations 

 have been carried out on the action of yeast on almost all 

 the possible intermediary products, with the object of 

 ascertaining whether they give rise on fermentation to 

 ethyl alcohol. The results obtained so far by this method 



