534 THE PHYSIOLOGY OF REPRODUCTION 



should not be used as an amesthetic and its use limited in normal 

 labour, for it has been shown that this drug produces a degeneration 

 of the liver cells and therefore might prove synergistic to a condition 

 of toxaemia which is already present, but the symptoms of which are 

 latent." Examination of the nitrogen distribution in the urine was 

 looked upon as an important index of an impending toxemia. And 

 one authority went so far as to state that when the ammonia 

 nitrogen rose to ten per cent, of the total nitrogen and vomiting- 

 had been present in the early months, emptying the uterus was 

 indicated. 



The extensive observations of Murlin l on the composition of the 

 urine in pregnancy, both in dogs and the human female, have thrown 

 doubt on this view of normal pregnancy as a pathological condition. 

 According to Murlin this view is based on a misconception of the 

 significance of the observed changes in the nitrogen distribution. He 

 also showed that the very high figures for the ammonia excretion in 

 eclampsia which have been obtained are due to the fact that in this 

 condition the urine has to be drawn with a catheter and that even in 

 the most experienced hands it is impossible to avoid introducing into 

 the bladder bacteria capable of decomposing the urine in the bladder. 

 With all the clinical signs of pre-eclampsia the nitrogen partition 

 may be normal up to tire development of convulsions and even during 

 the twenty-four hours following it. From analyses of 100 cases he 

 concluded that the average of the nitrogen distribution in the last 

 month of normal pregnancy does not markedly differ from the normal 

 non-pregnant condition. In individual normal cases the ammonia 

 nitrogen may rise to seventeen per cent, and the amino-acid unde- 

 termined nitrogen to. ten per cent, of the total nitrogen. But this 

 does not necessarily indicate an acidosis or an abnormal condition. 

 It is the result of the increased retention of nitrogen. In a normal 

 non-pregnant organism the bulk of the urea excreted represents 

 waste or excess nitrogen, which is split off and got rid of as urea. 

 During the end of pregnancy increasing amounts of this waste nitrogen 

 are being used up, as has been seen, by the mother for the foetus and 

 for its own tissues. Consequently the excretion of total nitrogen and 

 of urea falls and if the absolute amounts of ammonia excreted remain 

 unaltered, its relative amount is bound to increase, i.e. the " ammonia 

 index" rises. The same argument applies to the change in the 

 relative amounts of sulphates and neutral sulphur excreted in the 

 urine. 



1 Murlin, "Qualitative Effects of Pregnancy on the Protein Metabolism of 

 the Dog," Amer. Jour. PhysioL, vol. xxviii., 1911. Murlin and Bailey, loc. cit. 

 Murlin, " Observations on the Protein Metabolism of Normal Pregnancy and 

 the Normal Puerperium," Surgery, Gyimcology and Obstetrics, 1913. 



