146 SCIENCE PROGRESS. 



After disposing of Voit's experiments, Pfliiger considers 

 certain other arguments which have been adduced in favour 

 of the formation of fat from proteid. 



A. Bitches, during lactation, have been found to give a 

 milk richer in fat on a proteid diet than on a diet of fat. 

 Pfliiger points out that in this case it has not been proved 

 that the extra fat appearing in the milk has not been 

 derived from a transportation and change of the fat already 

 deposited in other parts of the body. 



B. Radziejewsky is quoted by Voit as showing that fat 

 taken in with the food is not directly deposited as such 

 in the body. Pfliiger points out that Radziejewsky's ex- 

 periments prove the exact opposite. Moreover the direct 

 deposition of fat has been shown by many subsequent 

 observers (Munk, Lebedeff). 



C. In fatty degeneration and phosphorus poisoning, 

 the fat is universally assumed to come from the disintegra- 

 tion of the proteids of the cell. Pfliiger points out that the 

 absolute amount of fat formed under these circumstances is 

 very small and may come from the transformation of carbo- 

 hydrates already existing in the body. 



D. In the ripening of cheese there is a formation of fat 

 from proteid, but in this case the change is effected by fungi 

 and not by animal organisms. It is possible too that, in 

 Hofmann's experiments on the production of fat by fly- 

 maggots on putrid blood, the fat was first formed by the 

 organisms of putrefaction and was merely eaten up by the 

 fly-maggots and deposited in their tissues. It has not been 

 shown that fly-maggots can convert the proteid of the blood 

 into fat in the absence of these low vegetable organisms. 



Pfliiger's own method of experiment and his results are 

 given at length in (4). In these he used dogs which were 

 trained to pass their urine when required. He points out 

 that only with such animals is it possible to obtain any 

 correct information of the nitrogenous metabolism. He 

 criticises severely the researches in which the urine was 

 collected by putting the dog in a cage with an inclined 

 bottom, since both urine and faeces adhere to the hairs of 

 the animal as he rolls over, and one can never be certain 



