ADVANCED PHYSIOLOGICAL CHEMISTEY 471 



A second condition which leads to an increased excretion of 

 ammonia salts, is the presence of free acids in the tissues. This occurs 

 in severe forms of Diabetes mellitus, where oxybutyric acid exists ; or 

 after the administration of mineral acids by the mouth. Now the 

 presence of free acids in the tissues is incompatible with life, 1 and in 

 order to neutralise the free acid some of the ammonia, which otherwise 

 would have been transformed into urea, is utilised. An examination of 

 the urine in these cases will show an increase in the ammonia excretion, 

 with a corresponding decrease in urea. Of course, where other bases 

 are present in sufficient amount to neutralise the acids present in the 

 blood, the ammonia is left alone. 



A third condition which influences the excretion of ammonia, and 

 more especially its relationship to urea, is disease of the liver. Thus in 

 acute yellow atrophy, where the liver cells become inactive, there is an 

 enormous increase in the amount of ammonia excreted and a correspond- 

 ing decrease in the urea. In phosphorus poisoning the same condition 

 exists, the protoplasm of the cells being replaced by fat, and thereby 

 rendered incapable of transforming the ammonia into urea. In less 

 severe disease of the liver it seems probable that a tendency to the 

 condition exists, viz. an increase of ammonia at the expense of urea. 

 An estimation of these two bodies, therefore, should always be made 

 where obscure disease of the liver exists, and although a disturbance in 

 the relationship between them does not of necessity imply hepatic 

 disease, it nevertheless furnishes a valuable aid to the diagnosis in 

 doubtful cases. 



CHAPTER XIII. 

 URINE CONTINUED. 



Estimation of the Inorganic Constituents of Urine. Each of these 

 may be determined by the usual gravimetric chemical methods, 

 but, in order to carry out this satisfactorily, a considerable amount 

 of chemical technique, as well as the use of an accurate chemical 

 balance, is necessary. It is usual, therefore, to employ instead a 

 titrimetric method which yields, in most cases, sufficiently accurate 

 results for physiological purposes, and which involves much less time 

 than does the gravimetric method. The principle of the method 



1 Thus, the presence of free acids in diabetes probably accounts for the occur- 

 rence of diabetic coma, of which complication the majority of diabetics die. 

 Similar symptoms of coma are produced by injecting acids into the blood vessels. 



