INFLUENCE OF LIVER ON FROTEID METABOLISM. 905 
nourished animal, there was an increase of ammonia salts in the blood. 
It is also a well-established fact that certain ammonia salts passed 
through the liver along with the blood become synthetised within the 
liver into urea. The actual form which such ammonia salts probably 
take is that of a combination with sarcolactic acid, which is also, 
as is well known, produced in muscle, and which is found, probably 
in combination with ammonia, in the blood generally. 1 These facts 
render it not improbable that the ultimate condition of the proteid 
which has been metabolised in muscle is lactate of ammonia (whether 
passing through the intermediate condition of creatine or not). This 
lactate of ammonia passing into the general circulation and being 
conveyed to the liver is there converted in mammals into urea, in 
birds into uric acid, in which form it is excreted by the kidneys. In 
conformity with this it was found by Marfori 2 that lactate of ammonia 
injected into the vein of a dog at the rate of 60 to 100 mgrms. per 
kilo, per hour, was wholly changed to urea. 3 The rest of the molecule, 
there can be very little doubt, is oxidised and got rid of in the form 
of carbon dioxide and water. 
What intermediate changes may be gone through between the 
splitting of the proteid molecule into a nitrogenous and non-nitrogenous 
part, and the ultimate oxidation of the 11011 - nitrogenous part into 
carbon dioxide and water, is a matter mainly of conjecture ; but since we 
find within the muscular tissue, as an almost constant constituent, 
glycogen, it is conceivable that in part at least the split-off non- 
nitrogenous portion of the proteid molecule may first become converted 
into that substance, and possibly into grape-sugar, to be subsequently 
further split up and oxidised to form the ultimate products of oxidation. 
That the proteid molecule can split up into a nitrogenous part and a 
part which is capable of "being converted into carbohydrate, is shown 
very strikingly by the phenomena of diabetes, whether natural and of 
the severe form, or whether due to the administration of phloridzin or 
pancreatic extirpation. In these cases, even when the diet is ex- 
clusively proteid, or even when food is altogether withheld and the 
starving animal is compelled to live mainly upon the proteids of its own 
tissue, sugar becomes formed in great amount, and must be produced by 
the transformation of proteids. It is not unreasonable to suppose that 
this is merely an abnormally heightened form of the normal condition 
of things, and that under ordinary circumstances a similar transformation 
of the proteid molecule may go on in the muscles, for in phloridzin 
diabetes at any rate 4 the formation of sugar is independent of the liver. 
With regard to the sulphur of the metamorphosed proteids, this 
1 Gaglio, Arch. f. Physiol., Leipzig, 1886, S. 400. Gaglio showed not only that lactic 
acid is constantly present in the blood, but that its amount is increased in blood perfused 
through various "surviving "organs (kidneys, lungs). See also p. 159 of this volume. 
V. Frey also obtained an increase of lactic acid in blood which had been perfused through 
"surviving" muscle (Arch. f. Physiol., Leipzig, 1885, S. 533). 
2 Arch.f. exper. Path. u. PharmaloL, Leipzig, 1893, Bd. xxxi. S. 71. 
3 Minkowski found that in geese, after extirpation of the liver, the ammonia of the urine, 
which in normal geese amounts to from 9 to 18 per cent, of the total nitrogen, was 
increased to from 50 to 60 per cent. (Arch.f. exper. Path. u. Pharmakol., Leipzig, 1886, Bd. 
xxi. S. 41; and ibid., 1893, Bd. xxxi. S. 214), whilst the uric acid almost disappeared. 
The ammonia was in the form of lactate, although in the normal animal there is no 
appreciable amount of lactic acid in the urine. 
4 In pancreatic diabetes, according to Marcuse ( Vcrhandl. d. physiol. Gesellsch. zu 
Berlin, 1893-4, S. 98), this is not the case. Frogs deprived of liver, as well as pancreas, 
although they lived 3 to 5 days, showed no glycosuria. 
