846 FORMATION OF UREA IN THE ORGANISM. 
alkalis are ammonia and amido-acids of the fatty and aromatic 
series (glycocine, leucine, and tyrosine). These three bodies, 
leucine, tyrosine, and glycocine, constantly occur in the 
animal body under normal conditions. Glycocine can be 
removed from the body in considerable quantities by the 
administration of benzoic acid, and leucine and tyrosine occur 
in pleuritic or ascitic exudations. Whenever albumin decom¬ 
poses and oxidation is hindered by the absence of haemo¬ 
globin, as is the case in pus, much leucine and tyrosine are 
found, but little or no urea; and when the oxidising power 
of the organism is diminished, as in acute atrophy of the 
liver and in phosphorus poisoning, much leucine and tyrosine 
occur in the urine, but scarcely any urea. These circum¬ 
stances led the authors to believe that the amido-acids of the 
fatty series, and perhaps tyrosine, were the intermediate links 
between albumin and urea. In order to test this hypothesis, 
they fed dogs on a diet containing a constant but small 
amount of nitrogen, and thus got a constant and small 
amount of nitrogen in the urine. They then gave the animals 
a quantity of leucine, tyrosine, or glycocine, in order to see if 
the amount of urea in the urine was increased, as it must be 
if these substances are transformed into it in the body. The 
result was, that after the administration of leucine or glyco¬ 
cine, the amount of urea in the urine was greatly increased 
and the nitrogen contained in the additional urea very nearly 
corresponded with that of the glycocine and leucine, clearly 
showing that these bodies are converted into urea. The urea 
was also increased by tyrosine, but not to so great an extent, 
and part of the tyrosine appeared unchanged in the urine and 
faeces. The authors therefore think that the greater part of 
the tyrosine is absorbed from the intestine, but is destroyed 
so slowly in the body that a part of it is excreted unchanged 
in the urine, while that portion which does undergo trans¬ 
formation is excreted as urea. When acetamide was given 
to the dogs, it was excreted unchanged, and no part of it 
was converted into urea. As amido-compounds analogous 
to acetamide are not excreted normally in the urine, the 
authors think that they are not formed during the decom¬ 
position of albumin in the body. Since amido-acids contain 
only one atom of nitrogen and urea contains two, it must be 
formed from them by synthesis, and the authors think it 
likely that bodies from the cyanogen group form the inter¬ 
mediate links. 
According to their idea, the albuminous substances con¬ 
tained in food take up water under the influence of the 
digestive ferments and are split up partly in the alimentary 
