Chemical Changes in Animal Organism. 315 



taken. One was killed, and the nitrogen and the fat of the 

 body ^vere estimated. The second was fed for four months 

 on barley, which was carefully weighed and analyzed, and 

 the fat and nitrogen which passed undigested through 

 the body in the faeces were also estimated. At the end 

 of four months the second pig was killed, and its 

 body analyzed. It was found that the animal contained 

 1*56 kilos more protein and 8*6 more kilos of fat than 

 the control animal which was killed at the age of ten 

 weeks. It had taken up with the food during the time of 

 feeding 7 '4 9 kilos of protein and 0*66 kilo of fat. If 

 the protein added to the body is subtracted from that 

 ingested as food, there is a remainder of 5 '9 3 kilos, which 

 might have given rise to the fat. This, however, is less 

 than the fat actually put on by the animal. The only 

 conclusion from this experiment possible is that the fat 

 was formed from the other chief constituent of the diet, 

 namely, the carbohydrates. Again, it is not possible to 

 ascertain the chemical changes which the carbohydrates 

 must undergo before they are converted into substances 

 with such a different chemical structure as the fats. 



Another example of a method of investigating inter- 

 mediary metabolism, which falls under the above heading, 

 has been already cited. Leathes and Miss Meyer Wedell 

 have shown that on feeding animals with fats and oils, fats 

 accumulate in the liver, the fatty acids of which, judged 

 by their iodine values, are more unsaturated than those 

 contained in the food. As unsaturated acids are generally 

 more readily oxidized than the corresponding saturated 

 derivatives, it would appear as if the removal of hydrogen 

 atoms is one of the first stages in the degradation of the 



O O 



complex fatty acids. 



