THE SEAT OF FORMATION OF UREA 687 



connection are sarcolactic acid and /3-oxy-butyric acid with its 

 derivative aceto-acetic acid. It is probable, however, that 

 oxalic acid and a large number of less well-known acids are 

 also produced during metabolism. The history of sarcolactic 

 acid in the body is only imperfectly understood. In health 

 it is produced in muscles and other tissues, and is found in 

 the blood but not in the urine. It must therefore be oxidised 

 in the body. But it is found in the urine in a large number 

 of conditions of disturbed metabolism ; the only one which 

 interests us in this connection is destruction of the liver. It 

 is found in the urine of men suffering from acute yellow atrophy 

 of the liver, and we have already seen that Salaskin and Zaleski 

 found it in the urine of their dogs. Minkowski demonstrated 

 its presence in the urine of geese after the liver had been either 

 excluded from the circulation or excised. He showed that 

 geese might live for twelve or more hours after the operation, and 

 might pass as much as 3*5 grm. of sarcolactic acid. At the 

 same time the uric acid was almost completely replaced by 

 ammonia. /3-oxy-butyric acid is not known for certain to 

 be a normal metabolic product, but it may be found in the blood 

 and urine in severe cases of human diabetes and in pancreatic 

 and phloridzin diabetes. In man the amount passed in a day 

 may be as much as 100 grm. Acidosis has also been produced 

 experimentally by placing mineral or organic acids in the 

 stomach of an animal. In all the experimental and patho- 

 logical acid intoxications it is found that the excretion of 

 ammonia is increased both actually and relatively to the total 

 N, and that this increase of ammonia is in mammals at the 

 expense of the urea. In order to account for this the view 

 has been put forward that ammonia is produced in metabolism 

 with the special object of neutralising acids simultaneously 

 formed, and of so saving for the body the important bases 

 Na, Ca, K, &c., which would otherwise have to be used. The 

 view is applied not merely to abnormal but also to normal 

 metabolism, and the ammonia in healthy urine is looked upon 

 as base which was required to neutralise acid and could not be 

 allowed to be converted into a neutral body like urea. That 

 ammonia can spare the bases of the body, and that this de- 

 fensive mechanism against acidosis is more highly developed 

 in man and carnivora than in the herbivora, has been shown 



