LOCALIZED ANOMALIES IN HUMAN EMBRYOS 51 



here we must rely largely upon our experience in human and in 

 comparative embryolog3^ A sharply defined, well formed white 

 embryo, with blood vessels shining through its transparent 

 tissues, is considered normal. If it is partly stunted and opaque 

 or disintegrating, it is considered pathological. A further study 

 of the normal embryo, however, shows that in many of these 

 specimens the membranes are decidedly pathological. For 

 instance, the villi may be deformed, diseased, atrophic or hyper- 

 trophic, or the contents of the amnion and the exocoelom may 

 be unusual. Nevertheless, in all of these cases we still classify 

 the embryos as normal, although fully cognizant of the fact 

 that the surrounding membranes are pathological; otherwise it 

 would be difficult to account for the great number of spon- 

 taneous abortions. The theory is that the embryo was devel- 

 oped under pathological conditions, but that the chorion was 

 not sufficiently affected to cause any apparent change in the 

 embryo. If an embryo included in this group is apparently 

 normal in all respects save one, we still consider it normal with 

 a localized anomaly. In fact we are gradually forced into this 

 position, as an embryo, considered at first to be normal, may 

 later on prove to have a localized anomaly, such as spina bifida 

 or cyclopia. As far as we can determine, such an embryo would 

 have been able to sur\'i\'e longer had not something happened 

 to its membranes, thus causing its expulsion. I am inclined to 

 believe that pregnancies of this sort, if carried to term, would 

 produce the ordinary monsters described by teratologists. As 

 the study of our collection of specimens is continued by different 

 members of the staff, localized anomahes, wlien found, are 

 recorded in our card catalogue, without, as stated above, neces- 

 sitating any rearrangement. WTien these anomalies are present 

 in normal embryos, the embryos are classed as normal, with 

 localized anomalies. 



The second group of specimens, which are termed patho- 

 logical, are in a way more interesting, and their study justifies 

 our method of classifying localized anomalies with normal 

 embryos. We have in this group a variety of changes ranging 

 from those found in fetus compressus down to complete disin- 



