Nutrition Studies. 59 



these later trials it is shown that 100 lbs. of digested starch or 

 digested fiber yielded about 24.8 lbs., and 100 lbs. of digested cane 

 sugar only 18.8 lbs., of body fat. 



82. Fat from pentosans. — Tho no experiments have yet been car- 

 ried on to show that body fat may be formed from pure pentosans, 

 it is certain that these carbohydrates aid in its formation. Kell- 

 ner^ fed oxen straw in which pentosans furnished 33 per ct. of the 

 energy. The large deposits of fat which followed must have come 

 in part from the pentosans of the food. 



83. Fat from protein. — When a liberal protein diet supplies the 

 animal with more energy than is necessary for its maintenance, not 

 only may a part of the excess protein be deposited in the body as 

 flesh, but the non-nitrogenous portion resulting from the cleavage 

 of protein may be converted into body fat or glycogen. Since body 

 fat may be derived from the carbohydrates, and since glucose and 

 glycogen may be formed from the proteins, it is reasonable to hold 

 that body fat may be formed from the protein of the food. Dem- 

 onstration of the direct formation of body fat from food protein is 

 difficult, however, as it is almost impossible to induce animals to 

 consume any large quantity of pure protein food. The consump- 

 tion of protein must be relatively large to maintain the nitrogen 

 equilibrium of the body, and so usually but a small excess avail- 

 able for the formation of fat remains above body requirements. 



Investigations by Cramer- with cats, and by Voit^ and Gruber* 

 with dogs which were fed large amounts of lean meat, show that 

 the protein it contained must have been the source of the fat which 

 was stored in their bodies during the trials, Henneberg,^ working 

 with dogs, concluded that 100 lbs. of protein may, upon decomposi- 

 tion, yield 51.4 lbs. of fat. Rubner," likewise experimenting witli 

 dogs, has shown that owing to the losses of energy which occur in 

 the decomposition of protein not more than 34.7 lbs. of fat can be 

 formed from 100 lbs. of protein in the food. 



Herbivora — the ox, horse, sheep, etc. — cannot be fed exclusively 

 on protein, since such feeding causes intestinal disorders. Kell- 

 ner,^ experimenting with steers, added wheat gluten, which is prin- 

 cipally composed of vegetable proteins, to a ration which was 

 already causing a considerable deposition of fat. The feeding of 

 100 lbs. of gluten caused the deposition of only 23.5 lbs. of fat 



' Loc. cit. ° Landw. Vers. Sta., 20, 1877, p. 394. 



" Ztschr. Biol., 38, 1899, p. 307. " Ztschr. Biol., 21, 1885, p. 250. 



^ Jahresber. Tier-Chem., 22, 1892, p. 34. ' Landw. Vers. Sta., 53, 1900, p. 452. 

 ^Ztschr. Biol., 42, 1901,1). 407. 



