76 THE SYNTHESIS OF FATS 



to carbohydrate, in amounts depending on the concentration of 

 the sugar and this is independent of the nature of the sugar. 



Maltose is more effective in promoting the storage of car- 

 bohydrate and less effective in bringing about the formation 

 of fat as compared with fructose, glucose and sucrose : the 

 presence of phosphate increases the amount of fat and de- 

 creases the amount of carbohydrate stored. The presence 

 of oxygen is an essential condition for this fat production. 



In the present consideration, the salient points of Mac- 

 lean and Hoffert's investigation are the relationship between 

 carbohydrate and fat and the possible substitution of carbo- 

 hydrate in the culture medium by salts of acetic, lactic and 

 pyruvic acids. 



Haehn and Kinttof * showed that the fungus Endomyces 

 vernalis was able to build up fat when grown on a medium 

 containing acetic aldehyde and even ethyl alcohol as the only 

 source of carbon, which possibly indicates that acetic alde- 

 hyde may be a stage in the conversion of sugar into fats. The 

 sequence they suggest is glucose -> pyro-racemic acid -> 

 acetaldehyde -> aldol -> glycerol esters. 



The evidence outlined above gives strong support to the 

 thesis that fats have their origin in carbohydrates : the 

 chemical aspect of this probability may now be considered. 



The striking recurrence of the eighteen carbon atom fatty 

 acids belonging to the various series exemplified by stearic 

 acid C 18 H 36 2 , oleic acid C 18 H 34 2 , linoleic acid C 18 H 32 2 , 

 linolenic acid C 18 H 30 O 2 gave rise to the suggestion that such 

 acids were produced by the direct union of three six-carbon 

 atom sugars ; there are, however, several reasons for rejecting 

 this hypothesis. In the first place, there is no particular reason 

 to exclude the association of hexoses with pentoses ; thus sup- 

 posing one hexose and two pentoses to be involved, an acid 

 containing sixteen carbon atoms would result ; a difficulty, 

 however, arises in the fact that a single molecule of a hexose 

 and a pentose respectively would result in a fatty acid con- 

 taining eleven carbon atoms, but it is a well-known fact that 



* Haehn and Kinttof : " Ber. deut. chein. Ges.," 1923, 56, 439. 



