934 



METABOLISM. 



animal poisoned by phosphorus J also affords strong presumption of the 

 conversion of proteid into fat. The fact that in the deposition of fat in 

 embryonic adipose tissue the fatty globules are preceded by albuminous 

 granules may also be given as evidence in the same direction. 



So important did the extent of such formation of fat from proteid 

 appear to Voit, that he endeavoured, as already stated, to account for the 

 fattening qualities of carbohydrate food by supposing that it mainly 

 acts by sparing the oxidation of the proteids (and fats), thus allowing a 

 larger amount of these to be transformed into body-fat. 2 In support of 

 his views, he pointed out that if the proteid molecule is supposed to be 

 split up, and a portion be removed in combination with the nitrogen 

 as urea, the carbon, oxygen, and hydrogen which remain are not very 

 different from the proportion of these elements which would be neces- 

 sary for the formation of fat. It was indeed calculated by Henneberg 3 

 that 51 '4 per cent, of proteid taken as food might, under the most 

 favourable circumstances, be supposed to be converted into fat. Kubner, 

 however, has shown that this estimate is too high. He calculates that 

 the utmost amount which could be converted into fat would be about 

 46 - 9 per cent. 



The view that the fat of the body is exclusively derived from the pro- 

 teid of the food is, however, no longer held by any physiologists, and Voit 

 has himself shown that it must in some circumstances be derived from 

 carbohydrate. 4 The above view cannot, indeed, be held, if we accept, as 

 we undoubtedly must, the conclusions to be drawn from experiments like 

 those of Lawes and Gilbert. These experiments do not by any means 

 exclude the formation of fat from proteid, but do exclude the possibility 

 of its being formed entirely from proteid, and not from any other article 

 of diet. That a certain amount of proteid is necessary to be added to the 

 diet of a fattening or suckling animal is a matter of everyday experi- 

 ence ; but it does not seem to be necessary that this proteid should be 

 greatly in excess of that which is necessary to make up for the proteid 

 lost from the tissues, or, in the case of the suckling animal, for that also 

 which appears as caseinogen in the milk. If, however, the amount of 

 proteid in the food is too much decreased, there is more call upon the 

 carbohydrates and fats of the food for the immediate production of 

 energy, and as a result there will be less of these to be transformed into fat. 



1 Storch, abstr. in Deutsches Arch. f. klin. Med., Leipzig, 1867, Bd. ii. S. 264 ; Bauer, 

 Ztschr. f. SioL, Miinchen, 1871, Bd. vii. S. 63 ; ibid., 1878, Bd. xiv. S. 527 ; Caseneuve, 

 Rev. mens. de tried, et chir., Paris, 1880, tome iv. pp. 265 and 444 ; Stolnikoff, Arch. f. 

 PhysioL, Leipzig, 1887, Suppl. S. 1. Bauer found in a fasting dog, to which phosphorus had 

 been administered, as much as 42 per cent, of fat in the muscles, and 30 in the dry liver 

 substance, as against 167 in the muscles and 10 per cent, in the liver of control dogs. The 

 nitrogen excreted is at the same time greatly increased, this also pointing to increased meta- 

 bolism of proteid, while there is at the same time a diminished excretion of carbon dioxide, 

 and correspondingly less oxygen taken in. A similar formation of fat from proteid in 

 phosphorus poisoning has been shown by Leo (Ztschr. f. physiol. Chem., Strassburg, 1885, 

 Bd. ix. S. 483) to occur in frogs. On the other hand, Lebedeff (Arch. f. d. ges. PhysioL, 

 Bonn, 1883, Bd. xxxi. S. 11) found in dogs which had previously been fed with linseed oil, 

 that the fat in the liver cells, which was formed after administration of phosphorus, had 

 the same characters as that Avhich had been laid on in the adipose tissue ; thus indicating 

 a transference of fat to the liver rather than its formation there from proteid. Stolnikow 

 found in frogs, after extirpation of the "fat-body," that the liver became enlarged, and fat 

 accumulated in it under conditions of both carbohydrate and proteid nutriment, even with- 

 out the addition of phosphorus to the diet. 



2 For further details of the evidence in favour of this view, see Voit, in Hermann's 

 "Handbuch," Bd. vi. S. 243-251. 



3 Quoted by Voit, Art. in Hermann's "Handbuch," S. 250. 



4 Siol Centralbl., Erlangeu, 1886-7, Bd. vi. S. 243. 



