52 



E. I. WERBER. 



which primarily interfere with normal development. Such 

 defects as rudimentary development of one or both eyes, con- 

 genital absence of both arms, hydrocephalus, possibly also cases 

 of congenital deafness, to mention only a few that are well 

 known to occur, can, in the writer's opinion, hardly be traced 

 to defective implantation. The results of investigations in 

 experimental teratology by Panum,^ Dareste^ and more recently 

 by Stockard^ and Bardeen* would seem to suggest that some 

 physico-chemical factors may be at work in a great number of 

 cases of pathological development. These factors may in some 

 instances be the primary cause of terata, while in other cases 

 they may be only secondary contributing causes. 



The experimental teratologists subjected developing ova in 

 very early stages to changes in the physico-chemical nature of 

 the environment and found that various monstrosities could be 

 produced under these conditions. It was impossible, however, 

 for them to control the results of experimentation, as they could 

 not predict the type of monster which would result from the 

 employment of the same factors. The experiments of Stockard, 

 where a more or less definite monstrosity — cyclopia or monoph- 

 thalmia — appeared with considerable certainty in a large per- 

 centage of embryos developing in magnesium chloride or alcohol 

 solutions, mark a distinct progress in this field of inquiry, because 

 they paved the way towards experimental control of monstrosities 

 occurring in nature. 



To the writer Stockard 's work suggested the possibility that 

 the monstrosities met with in higher animals and man may to a 

 certain extent be due to the influence of injurious substances 

 found in the circulation under pathological conditions. While 

 this hypothesis could not be applied to bacterial toxins on account 

 of insufficient knowledge, it seemed that some substances thrown 

 into the circulation in various metabolic diseases may be re- 



1 Panum, "Entstehung der Missbildungen," i860. 



2 Dareste, "Recherches sur la production de monstrosites," Paris, 1891. 



3 Stockard, C. R., " The Artificial Production of a Single Median Cyclopean Eye 

 in the Fish Embryo by Means of Seawater Solutions of Magnesium Chlorid," 

 Arch.f. Entwmech., Vol. XXII., 1907; "The Influence of Alcohol and Other Anaes- 

 thetics on Embryonic Development," Am. Jour, of Anat., Vol. X., 1910. 



^ Bardeen, C. R., Jour, of Experimental Zool., 1907; Am. Jour, of Anat., Vol. XI. 



