RESEARCHES ON PROTEID METABOLISM. 145 



chief aro-ument for the formation of fat from proteid is 

 afforded by some experiments of Pettenkofer and Voit, in 

 which the nitrogenous income and output of the animal 

 were measured, as well as the evolution of C0 2 . In many 

 cases in which the animal was fed on lean meat, it was 

 found that all the nitrogen taken in with the food appeared 

 in the urine, but there was a deficiency in the carbon ; so 

 that part of the carbon had been stored up in the body, 

 presumably as fat. In (3), Pfliiger criticises these experi- 

 ments in detail and shows that Pettenkofer and Voit's con- 

 clusions were founded on faulty assumptions, and that in 

 these experiments there was really a consumption and not 

 a deposition of fat. 



In the first place, Voit did not take into account the fat 

 and carbohydrate contained in the meat used, which in their 

 experiments were equivalent to icv8 grms. fat a day. More- 

 over, in reckoning out the daily balance sheet of the animal, 

 they made use of an erroneous analysis of the meat. Voit 

 did not analyse every separate sample of meat given to the 

 dogs, but assumed its composition from previous analyses of 

 meat. Voit, in previous analyses, found that meat con- 

 tained 3-59 per cent. N. For his balance sheets, however, 

 he arbitrarily adopts the figure 3 '4 per cent. N. According 

 to Voit, therefore, the proportion of nitrogen to carbon in 

 the meat used was ^^ • According to analyses by Rubner, 

 carried out in the Munich laboratory, it is ^, but this does 

 not take into account 0*5 per cent, glycogen contained in 

 the meat, so that the real proportion, according to Pfliiger, 

 would be ^"2 ' Making this alteration in the assumed 

 composition of the meat given, Pfliiger recalculates all 

 Pettenkofer and Voit's experiments, and finds that in all 

 of them the amount of carbon excreted exceeded the 

 amount taken in with the food, so that the animal was 

 really consuming the fat of its own body. In no case, 

 according to Pfliiger, can fat be produced in the body from 

 the proteid of the food. As the proteid of the food is 

 increased, so the nitrogenous metabolism rises. If any of 

 the proteid is retained in the body, it is retained as 

 proteid and not as fat. 



