LOCALIZED ANOMALIES IN HUMAN EMBRYOS 69 



I have already pointed out the difference in, frequency of 

 malformations and destructive changes as observed in the ovum 

 in tubal and in uterine pregnancies. Since the pubhcation of 

 my monograph on monsters, I have reconsidered the question 

 of tubal pregnancy, and the specimens mentioned in the present 

 paper are recorded in detail in a book on tubal pregnancy re- 

 cently published.^ 



It seems to me that the studies based upon our collection of 

 embryos as well as recent investigations in experimental embry- 

 ology, set at rest for all time the question of the causation of 

 monsters. It has been my aim to demonstrate that the em- 

 bryos found in pathological human ova and those obtained 

 experimentally in animals are not analogous or similar, but 

 identical. A double monster or a cyclopean fish is identical 

 with the same condition in human beings. In all cases, mon- 

 sters are produced by external influences acting upon the ovum; 

 as, for instance, varnishing the shell of a hen's egg or changing 

 its temperature; traumatic and mechanical agencies magnetic 

 and electrical influences, as well as by alteration of the character 

 of the surrounding gases, or by the injection of poisons into 

 the white of an egg. In aquatic animals, monsters may be 

 produced by similar methods. Whether in the end all malfor- 

 mations are brought about by some simple mechanism, such, 

 for instance, as alteration in the amount of oxygen or some other 

 gas, remains to be demonstrated. The specimens under con- 

 sideration show such marked primary changes in the villi of the 

 chorion and in the surrounding decidua that the conditions in 

 the human may be considered equivalent or practically identical 

 with those created artificially in the production of abnormal 

 development in animals. 



It would have been quite simple to conclude that the poisons 

 produced by an inflamed uterus should be viewed as the sole 

 cause, but when it is recalled that pathological ova occur far 

 more commonly in tubal than in uterine pregnancy, such a 

 theory becomes untenable. Moreover, monsters are frequently 



' Mall, Franklin P. On the fate of the human embryo in tubal pregnancy. 

 Publication No. 221, Carnegie Institution of Washington, 1915. 



