Animal Nutrition. 61 



fatly acids. He fed a starved dog lean meat and a large quantity 

 of fatty acids prepared from mutton suet. The animal, which 

 had shrunk 32 per cent, in weight during nineteen days, was fed 

 3,200 grams of flesh and 2,850 grams of fatty acids in fourteen 

 days, and increased 17 per cent, in weight during this period. 

 When killed, a well-developed layer of fat was found under the 

 skin, and also large deposits of fat on the internal organs. By 

 use of the knife, 1,100 grams of fat were separated, which 

 resembled mutton suet, and according to chemical analysis must 

 have contained at least 96 per cent, of neutral mutton suet. It is 

 known that fatty acids are formed from the fat of the food in the 

 digestive processes through the action of the pancreatic juice, 

 and the above experiment therefore practically proves that the 

 fat stored in the body of animals may be derived from the fat of 

 the food. Munk's findings have recently been corroborated by 

 Walker, also in experiments with dogs. ^ 



While experiments like those quoted above cannot be made 

 with Herbivora, there is sufiSicient evidence to establish the fact 

 that the fat of the food may, under favorable conditions, directly 

 contribute to the body fat and milk fat of animals. As will be 

 seen later on, however, the fat in the animal body is not derived 

 from one component of the food only, but generally from both the 

 fat and carbohydrates, or possibly these two in conjunction with 

 the protein of the food, according to the conditions of feeding and 

 the relative amounts of the different components fed. 



76. Fat from carbohydrates. — Liebig maintained as early as 

 1842 that the fat of the Herbivora must be derived in a great 

 measure from the carbohydrates of the food, but considered that 

 it might also be produced from its nitrogenous components. The 

 correctness of this view was questioned by leading scientists of 

 that time, although evidence in its favor was accumulating. In 

 1852 Lawes and Gilbert published the results of their pig-feeding 

 experiments, showing that a large portion of the fat stored in 

 tlie body of a fattening pig must come from other sources than 

 the fatty matter of the food. These investigators calculated the 



» CentralbL t Physiologie, IV, p. 590; Jahresbr. d. Thier Chemie, 21, 

 p. 32. 



