184 ■ EXPERIMENT STATION RECORD. 



lu calculating the results of these experiments it was necessary for 

 Yoit to assume some factor to represent the formation of fat from jiroteiu. 

 Although he himself calculated that 40.8 gm. of fat could be formed 

 from 100 gm. of protein, he adopted the figures wliich Henneberg had 

 found a year before, viz, that 51.4 gm. of fat could be formed from 100 

 gm. of protein. ^ From tbe analogous case of the fermentation of sugar 

 Henneberg Calculated that the nitrogen of the protein would be split 

 off in the form of urea. With the aid of these figures Yoit calculated 

 in his 2 experiments with cows that the fat contained in the food, 

 together with that formed from protein, was suflBcieut to account for not 

 only the fat in the milk, but also the milk sugar in it. Thus in this 

 case it was possible to disregard carbohydrates entirely in considering 

 the formation of fat, and very probably also in the formation of milk 

 sugar. 



Klihn published the results of his investigations in 1868. He fed 

 cows a ration rich in protein and poor in fat, while Yoit, as has already 

 been said, fed a fattening ration. In Kiihn's first experiment there 

 were 10 to 15 gm. and in the second experiment 35.5 to 39 gm. of fat in 

 the cow's milk in excess of the amount which could be accounted for 

 by the fat and protein in the food consumed. There remained no car- 

 bon which could serve for the formation of milk sugar, and its origin 

 must be sought in another source. In the first case there were found 

 303.5 gm. and in the second case 343.5 gin. of milk sugar. 



Yoit criticised these experiments on the ground that with such poor 

 food as Kiihii fed to his cows the body would lose fat. It was a ques- 

 tion if the secretion of milk which was observed could be maintained 

 on such diet ; in other words, whether the milk glands when no food was 

 consumed did not use the tissues of the body. 



In the formation of wax by bees the value of protein is not so easily 

 seen. In the experiments on this subject by Huber and Gundlach, 

 Dumas and Milne-Edwards the bees made in one case in 6 days an 

 amount of wax equal to 6 per cent of their own weight, and in another 

 case in 32 days an amount equal to 13 per cent of their weight. If 

 protein was lacking in the food the bees could easily have supi)lied the 

 small amount necessary from their own body tissue. 



These experiments only point at a formation of fat from carbohy- 

 drates. On the other hand, Berlepsch's exi:)eriments, in which the bees 

 were fed with honey and pollen, indicate decidedly a formation of fat 

 from protein ; the bees which were fed with honey and 117 gm. of pollen 

 made 33 gm. more of wax than the l)ees fed with honey alone. 



For various reasons Yoit doubted the accuracy of the results of experi- 

 ments made by Liebig, Boussingault, and Persoz on different animals, 

 and did not accept their conclusions. The experiments of Lawes and 



'W. Henneberg, Landw. Vers, Stat., 10 (1868), p. 437 and footnote p. 456; Tagebl. 

 Naturforsch. Versamml., 1876, Suppl., p. 169. Lawes and Gilbert, Rpt, 22d Meeting 

 British Assn. at Belfort, London, 1853, p. 323. 



