

CHAPTER XII. 



LYSIS AND RESORPTION OF CONCEPTUSES. 



It has long been known that considerable intrauterine retrogression of a con- 

 ceptus can occur in multiparous mammals. D'Outrepont, for example, on page 

 192 of the catalogue of his collection, is said (Muller, 1847) to represent the uterus 

 of a rabbit, in which an apparently full-term fetus is found near the distal end of 

 one horn, although the approximate portions of both horns contained but rem- 

 nants of fetuses, one in each. According to Muller, the enlargement in the right 

 horn contained a "cyst filled with rabbit hair embedded in a soft mass and that 

 on the left side a similar convolute of hairs without a cyst." This, as far as I 

 know, is the earliest reference to, even if not the earliest observation upon, a fetal 

 retrogression. But since rabbits are born naked, one is left to speculate upon the 

 validity of this observation. However, that the idea holds is indicated also by 

 some experimental work. 



Giacomini (1889) stated that he could effect absorption of the embryo in 

 rabbits within a few days by killing the embryo upon the seventh or eighth day 

 of gestation. Since this is just about the time that implantation of the ovum 

 occurs in the rabbit, I presume Giacomini really meant on the seventh or eighth 

 day after implantation. Giacomini added that these things show a close relation 

 between nodular and atrophic forms and the entire absence of embryos. Strangely 

 enough, Giacomini (1893) reported that puncture of or slight pressure upon the 

 implantation cavity on the ninth day of gestation was followed by complete 

 absorption of the conceptus by the thirteenth day, but he did not think that the 

 human blastodennic vesicle can undergo simple degeneration. 



Sokoloffs (1896) meager report also seems to indicate that in dogs bilateral 

 ovariotomy leads to the death of the embryo and to abortion of it and of the entire 

 conceptus. Strahl and Henneberg (1902) also found that conceptuses in different 

 stages of retrogression occur quite commonly among normally developed ones 

 in the ferret, marmot, and mole. They also found that the entire placenta and 

 probably also the fetal membranes, as stated by Hubrecht, are normally retained 

 for some time, even up to a month after parturition in the mole. Similarly, L. 

 Fraenkel (1903) was able to cause the death and also the uterine absorption of 

 conceptuses in rabbits up to the twentieth day of pregnancy, through destruction 

 of the corpora lutea. Fraenkel found that after 14 days all that remained in the 

 way of evidence of some pregnancies was an anemic ring which disappeared com- 

 pletely within three weeks. Henneberg (1903) also found that intrauterine death 

 and retrogression of the guinea-pig fetus can be effected experimentally through 

 various means, and, according to Koebner (1910), not merely ova or young fetuses 

 .are absorbed, but even the bones of older ones disappear completely under experi- 

 mental conditions in the rabbit. It would seem unlikely, however, that such could 

 be the case in any but the very earliest stages in the development of the skeleton, 

 for a considerable degree of acidity would have to develop in order to make this 



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