786 PHYSIOLOGY 



Definite evidence has, however, been brought forward, especially by 

 Lawes and Gilbert, for the transformation of carbohydrates into fats. In 

 these experiments two young pigs, ten weeks old, of the same litter, with 

 approximately equal weights, were taken. One was killed and the fat 

 and total nitrogen in the body estimated. From the amount of nitrogen 

 the maximum possible quantity of proteins present was calculated. The 

 second was fed on barley for four months. The barley was measured and 

 analysed, as well as the amount of undigested fat and protein that passed 

 through the animal. At the end of the four months the second animal 

 was killed and analysed. It was found that the animal contained 1-56 

 kilos more protein and 8-6 kilos more fat. It had taken up with the food 

 7-49 kilos more protein and 0-66 kilo fat. If we subtract the protein added 

 to the body (1-56) from that taken up with the food (749) there is a 

 remainder of 5-93 kilos which might possibly have given rise to fat. But 

 7-9 kilos of fat had been added in the body a far larger amount than 

 could possibly have arisen from the maximum amount of protein left over 

 for the purpose. At least 5 kilos of fat in this experiment must have been 

 derived from the direct conversion of the carbohydrates of the food. We 

 must conclude that fat can be formed directly from carbohydrates-, although 

 how and where this conversion takes place is at present quite unknown. 

 The fats formed on a carbohydrate diet are deposited chiefly in the sub- 

 cutaneous tissue. For the reasons already given the liver is found free from 

 fat under these conditions. In the fat formed from carbohydrate the two 

 saturated acids, palmitic and stearic acid, predominate. On this account 

 the fat has a firm consistency and a high melting-point. The fats of low 

 melting-point, such as olein, are absorbed more readily from the intestine 

 than those of high melting-point. Where the fat of the body is chiefly 

 derived from the fat of the food it tends to be of the more fluid acids and 

 contains a larger percentage of olein. 



Although it is impossible to trace out all the steps in the process of 

 conversion of sugar into fatty acid, we are acquainted with certain reactions 

 which may throw some light on the nature of the changes involved. If 

 we compare the formula of dextrose with that of the corresponding fatty 

 acid, caproic acid, 



CH 3 CH 2 OH 



CH 2 CHOH 



CH 2 CHOH 



CHOH 



^SA.M-* 



CH 2 



CH 2 CHOH 



COOH CHO 



we see that the conversion involves a considerable loss of oxygen. In 

 order to convert three molecules of glucose, C 6 H 12 6 , into one molecule 



