METABOLISM AND FOOD 77 



bacon or suet harder or softer ; to this point a 

 return will be made later. 



(/) Formation of body fat from carbohydrates. 



Although it must long have been seen in practice, 

 particularly in feeding pigs, that the carbohydrates 

 play a very important part in the formation of 

 fat, it was some time before definite proof was given 

 on this point. The opinion held was that next to 

 the fat of the food the splitting up of the protein 

 was the important source of fat. This being the 

 case, it was only necessary in an investigation 

 to calculate the amount of fat which could come 

 from these two sources, and if it were assumed 

 that all the fat and 51-4% (p. 65) of the decom- 

 posed protein passed into newly formed body fat, 

 then the increase of the latter would be directly 

 due to these two substances. 



When, however, in 1880-1 experiments were 

 made with a ration very poor in protein and fat, 

 it was observed that the quantity of fat stored in 

 the body was far greater than could have arisen 

 from the fat of the food, or from the decom- 

 position of the food protein. 



The investigations were carried out on three pigs 

 which were fed for 321 days before the experiment 

 began on a rather low diet. The animals, which 

 were very much alike as regards weight and condi- 



