The Metabolism of Lactating Women. 



89 



As for the individual nitrogenous substances excreted at this period but 

 little is known. Ammonia, which forms a larger percentage of the total 

 nitrogen with the advancement of pregnancy, gradually diminishes to the 

 normal amount. Urea, as might be expected, forms the greater part of the 

 increased nitrogenous excretion following childbirth and, according to 

 Grammatikati, is a maximum when milk appears in the breast and diminishes 

 with the weaning of the child. Other observers have not been able to 

 corroborate this observation or to ascribe the causal connection between urea 

 excretion and milk formation advanced by Grammatikati. 



The appearance of creatin in the urine of lying-in women was first 

 observed by Shaffer (5) and in dogs by Murlin (6). The present account is 

 more particularly connected with this excretion of creatin by puerperal 

 women. The analysis of such a condition seemed likely not only to furnish 

 important results as to the life history of creatin, but also to shed light on 

 the strange metabolic changes taking place in the body at this time. 



2. Tlie Relation of the Puerperal Creatin Excretion to the Involution of the Uterus. 



Other well recognised conditions in which creatin is excreted include 

 inanition and cancer of the liver (14), and since a striking feature about these 

 conditions is the rapid wasting of the patient, it has been assumed that when 

 the voluntary muscle breaks down, creatin is liberated into the blood-stream 

 and excreted. This explanation was extended by Shaffer (5) to explain the 

 puerperal excretion of creatin, but, in this case, the muscular tissue supposed 

 to supply the creatin to the blood-stream was not the voluntary muscle but 

 the involuntary muscle of the uterus. A serious difficulty, however, prevents 

 the acceptance of this explanation, in that, while voluntary muscle contains 

 abundant creatin, uterine muscle is quite , devoid of this substance. In a 

 previous paper (14), it was pointed out that creatin has a very limited 

 distribution in nature and can only be found in the cross-striated muscle of 

 vertebrate animals. The cross-striated muscle of invertebrates such as the 

 lobster and the king crab, and, on the other hand, the smooth muscle of 

 vertebrates, represent types of muscle which contain no creatin. Consequently, 

 creatin cannot be found in the smooth, unstriated muscle of the uterus. It 

 has been maintained that creatin and creatinin are present in tissues like the 

 uterus because extracts of such tissues frequently give the Weyl or the Jaffe 

 colour reactions. Both these colour tests are given by so many other 

 substances that they are unreliable* as proofs of the presence of creatinin. 



* Weyl's colour test with sodium nitroprusside and caustic soda is also given by 

 aldehyde, acetone, acetophenone, and aceto-acetic acid. 



Jaffe's colour test with picric acid and soda is given by any reducing agent. 



H 2 



