932 METABOLISM. 



also for the most part contain, in addition to a certain amount of 

 proteid, a large proportion of carbohydrate. In spite, however, of this 

 almost universal experience, it has been held by C. Voit 1 that the 

 carbohydrates of the food are not directly transformed into the fat of 

 the body, but that they only act in promoting the fattening of animals 

 by sparing the oxidation of proteid, so that the non-nitrogenous portion 

 of the proteid molecule may become transformed into fat. It has been, 

 in fact, altogether denied by Voit that the carbohydrates themselves can 

 be transformed by the animal economy into fat, in spite of the well- 

 established fact that in plants there frequently occurs, especially in the 

 ripening of many seeds, a considerable transformation of carbohydrate 

 material into fat. The question was^however, brought to the test of 

 direct experiment by Lawes and Gilbert. 2 These observers took two 

 pigs of the same litter, killed one as a control, and determined the total 

 amount of fat in its body, and kept another one alive for some weeks, 

 feeding it with proteid and an excess of carbohydrate food, and 

 determining the exact amount of proteid in such food, then killed it, 

 and determined the total amount of fat in its body. They found that 

 the amount of fat which had been added on during the time could not 

 be accounted for by supposing it to be derived from the proteids of 

 the food, since there was not sufficient proteid in the food during the 

 period of the experiment to account for more than two-thirds of the 

 fat which had been formed, even supposing the whole of its non- 

 nitrogenous moiety to have been transformed into fat. Therefore a 

 part at least of the fat formed must have been derived from the 

 carbohydrate in the food. 



This experiment has since been repeated by subsequent observers on 

 different animals, 3 and always with the same result, so that it may be taken 

 as conclusively proved that the carbohydrate of the food may be converted 

 into fat. The same fact may be shown by balance experiments, in which, 

 with nitrogenous equilibrium, there is carbon disappearance in the egesta, 

 showing that carbon is stored in the body in quantity more than to be 

 accounted for by the carbon of the proteid metabolised ; such laid up carbon 

 must be mainly stored as fat. 4 Nor is this formation of fat from carbohy- 

 drate by any means a unique phenomenon in the organic world. As we have 

 seen, it occurs in plants, in the seeds of which fat is deposited at the expense 

 of sugar or starch ; and in the process of fermentation of sugar, acids of the 



1 Hermann's "Handbuch," 1882, Ed. vi. S. 251 to 260. 



2 The very numerous original experiments by these observers, which were begun in 

 1847 in the private experimental agricultural station at Rothamstead, are described in 

 the following amongst other publications: Rep. Brit. Ass. Adv. Sc., London, 1852 and 

 1854; Journ. Hoy. Agric. Soc. Eng., London, 1849, 1851, 1852, 1853, 1855, and 1860; 

 Phil. Trans., London, 1859 ; Scient. Proc. Roy. Dublin Soc., 1864 ; London, Edinburgh, and 

 Dublin Phil. Mag., London, 1866 ; Journ. Anat. and PhysioL, London, 1877. An excellent 

 historical and critical account of the part taken by the various foodstuff's in the metabolic 

 processes of the animal economy is given by the same authors in Journ. Roy. Agric. Soc. 

 Eng., London, 1895, Ser. 3, vol. vi. pp. 47-141. 



3 Soxhlet, Ztschr. d. Landiv. Vereins in Bayern, 1881 ; B. Schultze (geese), Landiv. 

 Jahrb., 1882 ; Tscherwinsky, Landw. Versuchst., Berlin, 1883, Bd. xxix. S. 317. (These 

 are quoted from Neumeister, "Lehrbuch," S. 368.) See also Chaniewski (geese), 

 Ztschr. f. Biol., Miinchen, 1884, Bd. ii. S. 179 ; C. Voit, Sitzungsb. d. k.-bayer. Akad. 

 d. Wissensch. zu Miinchen, 1885, S. 288 ; Meissl, Strohmer, and v. Lorenz (pig), Ztschr. 

 f. Biol., Miinchen, 1886, Bd. xxii. S. 63 ; I. Munk (dog), Virchow's Archiv, 1886, Bd. 

 ci. S. 91 ; Rubner (dog), Ztschr. f. Biol., Miinchen, 1886, Bd. xxii. S. 272. 



4 Meissl and Strohmer, Monatsh. f. Chcm., Wien, 1883, Bd. iv. S. 801 ; Sitzungsb. d. k. 

 Akad. d. Wissensch., Wien, 1883, Bd. Ixxxviii. ; and Ztschr. f. Biol., Miinchen, 1886, 

 loc. cit. ; Rubner, loc. cit. 



