268 STUDIES ON PATHOLOGIC OVA. 



possible. Since it is believed that the development of acidity not only is slow but 

 also slight in embryonic tissues, Koebner's conclusion regarding the bones seems 

 to be open to some doubt. Wiener (1905) also found that autolysis is very slight 

 in tissues with an alkaline reaction and that a slight increase in acidity greatly 

 accelerates it. 



Fraenkel (1910 b ) extended and confirmed his work done in 1903 by a very 

 large series of experiments touching various phases of the corpus luteum problem, 

 and among other things concluded that one corpus luteum can protect at least 

 three ova sufficiently to insure continued development. 



Although the degenerating ova found by Huber (1915) in the rat were very 

 young, the significance of the facts would seem to be similar. Likewise Mall 

 (1915), while writing "On the fate of the human embryo in tubal pregnancy," 

 stated that "we have no data on the number of ova which disintegrate early, but 

 the study of comparative embryology warrants the conclusion that many young 

 ova degenerate and disintegrate. I am informed by Dr. Huber, who has studied 

 with great care much material among rats, that some of the fertilized ova break 

 down before implantation. The same seems to be true regarding the pig. We 

 usually find more corpora lutea in the ovaries than embryos in the uterus, indi- 

 cating that all of the ova do not produce normal embryos." Similar phenomena 

 also were reported by Meyer (191 7 a ), in regard to young conceptuses in the guinea- 

 pig. Curtis (1915) also reported the absorption of ova in guinea-pigs in con- 

 sequence of the injection of extracts of the human placenta, but unfortunately 

 Curtis did not give convincing evidence regarding his knowledge of the presence 

 of pregnancy in the animals concerned, nor did he make a microscopic examination. 

 Since Curtis stated that 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 experi- 

 mental 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 may well show a 

 greater tolerance to the presence of dead fetal tissue and also greater resorptive 

 power. Robinson (1904) stated that Vernhout showed that maternal 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 Dasyurus. Jenkinson (1913) also stated that in Perameles the 

 allantois and its blood-vessels are regularly absorbed through the agency of ma- 

 ternal leucocytes by the parturient uterus and that fetal tissues are absorbed some- 

 what 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 an inch long in the 

 kangaroo, it is clear that absorption of the secundines at this stage of development 



