324 LECTURE XIV. 



The conversion of albumin into fat was for a long time looked upon as 

 an established fact, albumin being even considered as the main source of 

 the body fat. This conception originated with Voit and Pettenkofer, 1 

 as an outcome of their experiments on metabolism. Since the time when 

 E. Pfliiger 2 critically examined the values given by the above authors, 

 the belief in the production of fat from albumin has been more and more 

 doubted, this being especially true since many observations, undertaken 

 in order to show such effects, have indicated that the above conclusions 

 were erroneous. Pettenkofer and Voit fed dogs with meat as free as 

 possible from fat. They found all of the nitrogen of the ingested albumin 

 present in the excretions, but only a part of the carbon. It was natural 

 to conclude from this, as we have already indicated, that the portion of 

 carbon which did not leave the organism in combination with the nitro- 

 gen, was utilized for the production of fat. Pettenkofer and Voit reached 

 this conclusion owing to the fact that the}' had assumed 1 : 3 . 68 to be the 

 relation of nitrogen to carbon in meat free from fat. Pfliiger, after allow- 

 ing for glycogen, reduces this value to 3 . 22, while Rubner places it at 3 . 28. 

 If we apply these changed values to the results of Pettenkofer and Voit, 

 we find that the assumption that fat is produced from albumin no longer 

 has any support. 



M. Kumagawa 3 has recently tried to solve the problem in the following 

 manner. He caused two dogs from the same litter to fast for 24 days. 

 One of the animals was then killed and analyzed. The second dog for 

 quite a long period was fed a liberal supply of horse meat (49 kilograms 

 in 49 days). The body weight rose from 6.08 to 10 kilograms. The 

 fat content of this animal at the beginning of the experiment must 

 have been about 120 grams. The other dog contained this amount. 

 The animal under experiment showed 1087 . 7 grams of fat on being killed. 

 The meat fed to this dog, however, contained 356 grams of glycogen and 

 1084 grams of fat. The amount of fat in the food, therefore, would of 

 itself have been sufficient to cause this increase. 



Although we must admit that no satisfactory proof has been obtained 

 by experiments on metabolism as regards the transformation of albumin 

 into fat, we must not forget, on the other hand, that these results merely 

 give us a rough idea of the whole interchange of material, but never the 

 finer details of cell activity. It is still a very remarkable fact that such a 

 small portion of the carbon in albumin should leave the organism in com- 



1 M. Pettenkofer and C. Voit: Ann. Supp. 57, 361 (1862). C. Voit: Z. Biol. 5, 106 

 (1869); 6, 371 (1870); 7, 433 (1871). Handbuch der Physiologic des Gesamt- 

 stoffwechsels und der Fortpflanzung, Leipsic, 1881. Ueber die Ursachen der Fett- 

 ablagerung im Tierkorper, Munich, 1883. 



2 E. Pfliiger: Pfliiger's Arch. 50,98 (330 and 396) (1891); 51,229 (1892); 52, 1 

 (1892); 68, 176 (1897); 77, 521 (1899). 



3 M. Kumagawa: Communication from the University of Tokio (1890). 



