RESORPTION OF CONCEPTUSES. 285 



injections of defibrinated human blood had the same effect as 

 the injection of extracts of the human placenta, and that the 

 injection of extracts of guinea pig placenta and of guinea pig blood 

 had no effect whatever, one can not help but feel decidedly 

 skeptical regarding the trustworthiness of his experimental 

 proof. 



It is well to remember in this connection that phenomena 

 which occur in other mammals, or conclusions drawn from these 

 phenomena, must be used with caution when referred to man. 

 The uteri of other mammals well may show a greater tolerance 

 to the presence of dead fetal tissue and also greater resorptive 

 power. Robinson, '04, stated that Vernhout showed that mater- 

 nal tissues are not shed at the time of birth in the mole, and that 

 some of the fetal tissues are retained to be absorbed later. Hill, 

 it seems, found the same thing to be true in Perameles and Da- 

 syurus. Jenkinson, '13, also stated, that in Perameles, the 

 allantois and its blood vessels regularly are absorbed through 

 the agency of maternal leucocytes by the parturient uterus and 

 that fetal tissues are absorbed somewhat similarly in Dasyurus. 

 However, since the young of some marsupials are in a very 

 immature state during the first months of gestation and are then 

 transferred to the marsupium as naked little fetuses said to be 

 only about one inch long in the kangaroo, it is clear that absorp- 

 tion of the secundines at this stage of development would be 

 something quite different from their resorption at the end of the 

 gestation period in other mammals. 



Although we have considerable evidence regarding retro- 

 gression and the partial or even the total intrauterine absorption 

 of conceptuses in various mammals, I have not been able to find 

 any conclusive evidence in the literature regarding the occurrence 

 of this phenomenon in man. It is true that cases of Frankel, 

 '03, Polano, '04, Rosenkranz, '03, and also cases reported by 

 others are referred to as such examples, but a careful examin- 

 ation of the reports shows that those cases hardly can be regarded 

 as falling under the head of intrauterine absorption of ovum, 

 embryo or fetus. It is true that in the cases of Polano and 

 Rosenkranz, the skeletal elements only were seen to have been 

 discharged, but in the case of Polano the amniotic fluid never- 



