932 ME TABOLISM. 
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 lie 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 
carboh} T drate 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," 18S2, 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: — Pep. Brit. Ass. Adv. Sc, London, 1852 and 
1854; Journ. Boy. Agric. Soc. Eng., London, 1849, 1851, 1852, 1S53, 1855, and 1860; 
Phil. Trans., London, 1859 ; Scient. Proc. Boy. 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 foodstuffs in the metabolic 
processes of the animal economy is given by the same authors in Journ. Boy. Agric. Soc. 
Eng., London, 1895, Ser. 3, vol. vi. pp. 47-141. 
3 Soxhlet, Ztschr. d. Landw. Verems in Bmjcrn, 1881; B. Schultze (geese), Landiv. 
Jahrb., 1S82 ; Tscherwinsky, Landiv. 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, Sitzimgsb. d. k.-bayer. Akad. 
d. JFisscnsch. zv Mwnchen, 1885, S. 288 ; Meissl, Strohmer, and v. Lorenz (pig), Ztschr. 
f. Biol., Miinchen, 1886, Bd. xxii. S. 63 ; I. Munk (dog), Virchoiv's Archiv, 1886, Bd. 
ci. S. 91 : Fullmer (dog), Ztschr./. Biol, Miinchen, 1886, Bd. xxii. S. 272. 
4 Meissl and Strohmer, Monatsh.f. Chan., Wien, 1883, Bd. iv. S. 801 ; Sitzungsb. d. k. 
Akad. d. Wisscnsch., Wien, 1883, Bd. lxxxviii. ; and Ztschr. f. Biol., Miinchen, 1886, 
loc. cit. ; Rubner, loc. cit. 
