92 



Mr. E. Mellanby. 



[Oct. 3, 



3. Evidence of the Relation between the Puerperal Excretion of Creatin and 

 Mammary Gland Activity in Women. 



Pregnant rabbits, like pregnant women, excrete abnormal quantities of 

 creatin. In fact tbe estimation of the creatin in the urine of a rabbit is a 

 useful means of diagnosing pregnancy. It may be well to state that in my 

 experience all rabbits, male and female, excrete small quantities of creatin. 

 Oxen also, independently of sex differences, normally excrete creatin in 

 addition to creatinin. This observation, affecting herbivorous animals, is in 

 marked contrast to the total absence of creatin from the urine of normal 

 people. When I started to investigate the puerperal excretion of creatin, 

 rabbits seemed to be the best animals for examination. It was surprising, 

 however, to find that the excretion of creatin by rabbits stops immediately 

 after delivery, and consequently they were useless for this investigation. 

 One possible factor suggested itself as an explanation of this difference 

 between rabbits and human beings, namely, that rabbits eat their placentae 

 after delivery. It might be imagined that the proper performance of the 

 functions of the organism after parturition depended upon the presence of 

 certain chemical groupings, which were supplied by the digestion and 

 assimilation of the placenta ; but that, in the human being, since no placenta 

 was available, the substances had to be supplied at the expense of other 

 tissues such as the muscles, with the result that creatin was liberated and 

 excreted at the time of the transference of material. If natural craving for 

 animal food is any indication of physiological needs, then it is certain that 

 female animals require the chemical substances of tissues such as muscle 

 after parturition. The longing which such women have for meat has its 

 analogy in the lower animals in their eating placentae and frequently their 

 young. In the case of herbivorous animals this seems to be the only time in 

 their lives that they are carnivorous and may have some special significance 

 such as the urgent requirements of the animal organism for substances such 

 as extractives. 



From this point of view, therefore, a cow was allowed to eat its placenta 

 after parturition, in order to see whether the creatin excretion would be 

 suppressed; The following figures were obtained : — 



