ABNORMALITIES OF THE MAMMALIAN EMBRYO OCCURRING 



BEFORE IMPLANTATION, 



The occurrence of monstrosities, degenerative changes, and other abnormal 

 conditions of the mammalian embryo brings up so many questions of scientific 

 and practical interest, attended by such difficulties of approach, that it seems in 

 order to report some recent observations which, though few in number, afford 

 evidence of a positive character with regard to one of the points now in dispute. 



Mall, in his several contributions on the nature and significance of abnor- 

 malities of the human embryo, never hesitated to assert the opinion that all these 

 changes could be attributed to disturbances of nutrition due to faulty implantation 

 of the ovum in the maternal uterine mucosa. This conviction was based on two 

 grounds; first, that defective implantation could actually be observed in many of 

 the abnormal human embryos which had come into his hands; second, that experi- 

 mental teratologists had produced in amphibia, by the application of chemical 

 poisons which presumably hindered the embryonic nutrition, all sorts of abnor- 

 malities resembling many of the known mammalian terata. 



This hypothesis has never been subjected to critical test in the human species, 

 because of the lack of specimens from stages prior to implantation; but the possibility 

 of attacking it on logical grounds was seized by Kellicott, who pointed out (partly 

 on the basis of his own remarkable experiments on the production of abnormalities 

 in fish embryos by the action of low temperatures) that the onset of such changes 

 might date from the earliest stages of cleavage of the ovum. He suggests that the 

 cause of abnormal and monstrous development is to be found in disturbance of the 

 normal organization of the ovum and he definitely considers the possibility that in 

 mammals the disturbing cause might be found operative before as well as after 

 implantation. 



A year before Kellicott's contribution Huber had published an account of a few 

 observations on abnormalities in very young embryos of the albino rat. His series 

 included cases of separation of the first two blastomeres into half -embryos, incom- 

 plete or retarded segmentation, degeneration of ova at the end of the segmentation 

 period, and abnormal formation of the segmentation cavity, all occurring in embryos 

 which were lying free in healthy uteri. Since faulty implantation could be excluded, 

 Huber was inclined to consider these abnormalities due to disturbances inherent 

 in the ova. 



The specimens described herein were obtained during the collection of a series 

 of early embryo pigs. Figure 1 shows two of these embryos that were found 

 among others in a healthy, normal uterus. One (A) is a normal blastodermic vesicle 

 which would appear, by comparison with Assheton's well-known stages, to be about 

 7 days old; figure 7 A, plate 2, illustrating the same ovum, displays its delicate, filmy 

 texture, with clearly outlined nuclei, and the developing embryonic area below the 



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