LOCALIZED ANOMALIES IN HUMAN EMBRYOS 71 



chorion, and this also soon disintegrates, leaving only the chor- 

 ionic membrane which in turn collapses, breaks down and finally 

 disappears entirely. In older specimens, on the other hand, 

 the process of destruction takes place more slowly and thus we 

 account for a succession of phenomena which correspond with 

 the seven groups of pathological ova recognized and given in 

 the various tables appended. 



In my original study, I really went, I believe, a step farther 

 than Kellicott in his discussion of monsters, as he dropped the 

 subject by stating that the embryo is a monster simply because 

 it is disorganized. I attempted to analyze the process of dis- 

 organization more thoroughly and demonstrated that when 

 disorganization begins it is accompanied by cytolysis, but as 

 it progresses more rapidly it results in histolysis, and that these 

 two processes do not act with equal severity on all parts of the 

 embryo. When we consider the whole ovum, it is the embryo 

 itself which is first destroyed; while within the embryo the cen- 

 tral nervous system or the heart is the portion which is first 

 affected. Morphologically, these changes are accompanied by 

 a destruction of certain cells and tissues, leaving other portions 

 which continue to grow in an irregular manner. For this reason 

 I speak of the tissues which are first affected as more susceptible 

 than the others. The entire process of disorganization, result- 

 ing in an irregular product, I have termed dissociation. In 

 a general way this explanation is accepted by Werber in his 

 recent studies, but he employs the term blastolysis instead.^" 



At the time I prepared my paper on monsters, Harrison was 

 just beginning his interesting experiments in tissue culture in 

 our laboratory. Since then this method of study has given us 

 clearer insight into the independent growth of tissues. I was 

 fully convinced from the study of pathological embryos that 

 tissues continue to grow in an irregular manner, thus arresting 

 normal development; but since we are more familiar with the 



10 Werber, E. I. Experimental studies aiming at the control of defective and 

 monstrous development. A survey of recorded monstrosities with special atten- 

 tion to the ophthalmic defects. Anat. Rec, vol. 9, 1915. Also: Blastolysis as 

 a morphogenetic factor in the development of monsters. Anat. Rec, vol. 10, 

 1916. 



