CHANGES DURING PREGNANCY 535 



Murlin has pointed out that some of the high ammonia indices 

 obtained in eclampsia and also in normal pregnancies are due to 

 decomposition occurring in the bladder, when a catheter has been 

 used. Even with the strictest aseptic precautions it is impossible to 

 prevent a plug of mucus being pushed into the bladder. Catharsis is 

 another factor which may raise the ammonia index considerably by 

 temporarily lowering the nitrogen intake. 



There is no doubt that in abnormal pregnancies, particularly in 



the pernicious vomiting of pregnancy, there is an actual increase both 



in the relative and in the absolute amounts of ammonia excreted. 



The ammonia index may rise to 30, 40 and even 70 against the 



normal index of 4 to 8. But this condition necessarily involves a low 



nitrogen intake which may amount to star\'ation. This in itself 



raises the ammonia index. In addition, there is frequently, if not 



always, a formation of considerable amounts of aceto -acetic acid and 



oxybutyric acid which lead to an increased excretion of ammonia and 



thus raise the ammonia index. It has been suggested that the high 



ammonia excretion is due primarily to a faulty protein metabolism 



which is specific for pregnancy. But the formation of the acetone 



bodies is in itself an adequate explanation of the increased ammonia 



excretion, and it is difficult to understand why so many observers 



refuse to attach any importance to the presence of these substances. 



It is even more difficult to understand why some workers have carried 



this neglect so far that they record long tables of analyses for the 



nitrogen distribution of the urine which sliow exceptionally high 



values for the ammonia index and completely omit even to test 



qualitatively for the presence of the acetone bodies. The only 



observations which have paid due attention to this point are those of 



Gilliatt and Kennaway^ who found a close parallelism to exist 



between the amount of the acetone bodies present and the ammonia 



excretion. The amount of acetone bodies present in their cases was 



too high to be accounted for as a direct result of starvation. They 



are inclined to look upon the excessive formation of these bodies as 



the primary cause of the condition, and draw an analogy with the 



similar conditions of cyclic vomiting in children. The point is of 



some practical importance, because a persistent high ammonia index 



is regarded by many authorities as an indication for emptying the 



uterus. The ammonia index can only be determined by a skilled 



worker in a special laboratory, and for its proper appreciation requires 



a knowledge of the total nitrogen intake of the patient, i.e. a collection 



of the urine excreted for twenty-four hours. A good estimate of 



1 Gilliatt and Keunaway, " Some Observations upon Cases of Vomiting in 

 Pregnancy," Qttai: Jour. Medicine, vol. xii., 1918.. This paper contains also a 

 critical survey of the literature on the metabolism in this condition. 



