STORAGE OF FAT IN THE BODY 129 



must be formed from proteid; hence the increase of proteid destruction when 

 carbohydrates are excluded from the diet. Since in such experiments on man 

 the N-excretion rose some 5 g. per day, the daily requirement of carbohydrates 

 would amount to about 32 g. (5 X 6.25 = 31.25; proteid Cal. = carbohydrate 

 Cal.). 



10. STORAGE OF FAT IN THE BODY 



Voit laid special stress upon proteid as the most important source of the 

 fat which is stored in the body. Using the ratio of N:C in proteid as found 

 by Voit and Pettenkoffer, their experiments on the state of equilibrium actually 

 show that a considerable portion of the C ingested in the form of proteid was 

 retained. Since the formation of glycogen was never very large, Voit and Pet- 

 tenkoffer were fully justified in concluding that some of the C was retained as fat. 



But the percentage of C in proteid is not so high as Voit and Pettenkoffer 

 supposed. Calculating their results on the basis of 1:3.28, the ratio of N:C 

 now generally accepted, a very different conclusion is reached. Pfliiger has 

 shown that instead of 57.8-58.5 g. of fat, which Voit and Pettenkoffer estimated 

 as the amount stored in the dog as the result of feeding 2,000 g. of meat per 

 day, the newer ratio allows only 11.8-13.6 g., and that with 1,500 g. of meat 

 practically no fat could have been stored. We are compelled, therefore, to con- 

 clude that these experiments contain no proof of a transformation of proteid 

 into fat. 



Later, however, Creiner obtained in the cat a retention of C from excessive 

 meat feeding which he regarded as a safe indication of the production of fat 

 from proteid. The cat excreted 11.2 g. of N per day and 31.2 g. C per day. But 

 calculating the C from the N on the basis of the ratio of 1:3.2 would give 

 35.7 g. C as the amount ingested. Since only 31.2 g. of this was eliminated in 

 the excreta, 4.5 g. of C per day must have been retained, and in seven days this 

 would amount to 31.5 g. According to Cremer's subsequent analysis the ani- 

 mal's body contained not more than 40 g. of glycogen with 18 g. C. The remain- 

 der of the 31.5 g. of C, namely 13.5 g., must therefore have been laid on as fat. 

 Unfortunately this experiment is quite too short and stands too much alone 

 to be accepted as a positive demonstration of the point. (Gruber accomplished 

 a retention of 81.9 g. C in a similar experiment on a dog, but the amount of 

 glycogen was not determined.) 



The other ground on which Voit based his idea that proteid is an important 

 source of fat, was the degeneration of proteid under some circumstances into 

 fat, and the great production of fat in the larvae of blowflies living exclusively 

 on meat. As regards the former, we now know that, at least in the case of the 

 phosphorus poisoning of the frog (Athanasiu), the supposed fatty degeneration 

 is in fact an infiltration of fat transported from the fatty deposits of the body 

 and deposited in the cells, instead of a formation in situ by the destruction of 

 proteid. Whether all forms of fatty degeneration are to be explained in the 

 same way, has not yet been settled. Lindemann has found that the fat of the 

 degenerated cardiac tissue is different in some essential respects from the fat 

 deposited elsewhere in the body, as about the kidneys and under the skin. This 

 fact, however, does not constitute strict proof against an eventual transportation 

 of fat, for it is easily conceivable that the fat might undergo some change in 

 the process of its liberation from the depository whence it came. 



Pfliiger explains the occurrence of fat in the larvaB of blowflies which lived 

 on blood, as observed by Hofmann, by supposing that the fat was formed from 

 the blood under the influence of Bacteria, and was merely absorbed as such by 



