SECT. 2] 



AND WEIGHT 



377 



embryo with the growth of the membranes, it is interesting to see 

 that for the first month the latter weigh much more than the former, 

 after which, for a certain period, they grow together at the same 

 rate. But soon the curves diverge, and the membranes hardly grow 

 any more, while the embryo continues to increase greatly in size. 

 Evidently when the membranes and placenta have reached a sufficient 

 size to meet the utmost further demands of the embryo they grow 

 no more. There can be little doubt that the size of the placenta 

 exercises an influence on the growth of the embryo, and is of the 

 highest importance from the point of view of embryonic nutrition. 



The amniotic liquid bears the same relationship as regards weight 

 to the embryo as do the placenta and the membranes. 



100 



Fig. 27. 



Fig. 27 shows Draper's curve for the length of the embryonic 

 guinea-pig. 



Ibsen's work led to much the same conclusions as regards the 

 relations between embryo and adnexa as that of Draper. Ibsen 

 found that the number of foetuses in the uterus exerted an effect 

 on the growth-rate of each one, thus the larger the litter the slower 

 the rate of growth of the individual foetus. The early growth of the 

 placenta is more rapid than that of the foetus, but they reach the 

 same weight on the 25th day, after which the foetus outstrips the 

 placenta very soon. Placental weight and the weight of the mem- 

 branes towards the end of pregnancy are closely correlated with 

 uterine crowding, but this is not the case with the decidua basalis, 

 which corresponds to the maternal part of the placenta. Minot con- 

 sidered that the amniotic fluid of the cow and of man decreased in 



