THE ORGANIC CONSTITUENTS OF THE URINE. 225 



this, indeed, we have abundant proof. It has been shown that in 

 diseases of this organ which are associated with an extensive destruc- 

 tion of the glandular elements a diminished amount of urea is found 

 in the urine, while ammonia and lactic acid are present in increased 

 quantity, and the mono-amido acids may appear as such. In cases 

 of this kind as much as 37 per cent, of the total amount of urinary 

 nitrogen has been found in the form of ammonia. In the mammal, 

 moreover, symptoms of carbamic acid poisoning are observed when 

 the liver is excluded from the general circulation, and, as has been 

 shown, the formation of urea from ammonium lactate or carbonate 

 may be demonstrated in the isolated livers of dogs. As negative 

 results were obtained by von Schroeder when blood containing am- 

 monium carbonate was passed through the kidneys and through the 

 isolated hind-quarters of dogs, the conclusion suggests itself that in 

 these organs a formation of urea does not occur. This inference is, 

 however, not admissible in the light of our modern knowledge of 

 the origin of urea, for we can readily conceive that although a syn- 

 thetic formation from ammonium carbonate may not occur in these 

 organs, it is nevertheless possible that it may originate in a different 

 manner. 



The transfusion experiment, after all, only shows whether or not a 

 new body can be formed in the organ under investigation from other 

 substances which are passed through it as such. Before deciding 

 that urea cannot be produced in these parts it would hence be neces- 

 sary to experiment with all those substances which can be made to 

 yield urea in the test-tube, and which we know to occur in the ani- 

 mal body. In the spleen, where arginin, for example, is known to 

 occur, it would be of interest to ascertain whether urea is produced 

 hero when blood containing arginin is passed through the organ. 



If we accept the modern doctrine that urea not only originates in 

 the animal body in different ways, but that it may also be formed in 

 other organs besides the liver, we can also understand why it is that 

 in certain diseases of the liver the diminution in the formation of 

 urea is not always proportionate to the extent of parenchyma to us 

 degeneration, and that no case has been reported in which the 

 formation of urea ceased altogether. It is also made clear why 

 urea is found in the urine of birds and reptiles, although a synthetic 

 production of the substance manifestly does not occur in these 

 animals. Its origin is here no doubt to be sought in its formation 

 from such bodies as kreatin, kreatinin, arginin, and the like. 



Nitrogenous Equilibrium. The albumins, of course, are the ulti- 

 mate source of the urea. According to Pettenkofer, they exist in 

 the body in two forms, viz., as organized albumin which is built up 

 into tissues, and as so-called circulating albumin which is present in 

 excess of what is actually required, and is broken down directly 

 and eliminated in the urine without having entered into the con- 

 struction of the body proper. This portion of the albumin furnishes 

 the greater portion of the urea, while the organized albumin repre- 



