486 E. I. WERBER 



D. Deformities of the brain 537 



E. The microscopic anal3'sis of some teratomata (the 'solitarj' eye' 



and the 'isolated eye') 541 



F. The microscopic anatomy of some amorphous monsters 553 



IV. Concluding remarks 558 



V. Summary 568 



VI. Literature cited 571 



I. IXTRODL'CTION 



A review of the literature shows us that we are at the present 

 time confronted with two theories regarding the causal genesis 

 of monsters. The first and older one, the amniotic theorj^, is 

 essentially a mechanical theory, while a more recent one which 

 is based on recent experiments on the influence of chemical 

 alterations of the egg's environment, ixiight be spoken of as the 

 chemical theory of teratogenesis. 



The amniotic theory maintains that terata are due to anoma- 

 lies of the amnion, which latter, by adhering too closely to the 

 embryo or constricting it, is thought to bring about the various 

 well known malformations. The inadequacy of this assump- 

 tion has in recent years been repeatedly pointed out.* It is a 

 well known fact that amniotic anomalies are found relatively 

 rarely in malformed ova. In one hundred and sixty-nine patho- 

 logical ova which Mall ('08) has examined he asserts that he 

 has found not a single case of anomaly of the amnion. Wherever 

 amniotic adhesions are found. Mall, I believe rightly -regards 

 them as incidental. It is not impossible that they may be 

 syngenetic with some terata, i.e., due to the same causes which 

 brought about the developmental deviation of the embryo. This 

 might particularly apply to the experimental terata of Dareste 

 ('91) and others, in which anomalies of the amnion were found. 

 On the whole, it might well be said, that in view, particularly, 

 of experimental results on anamniotes, the amniotic theory 

 would hardly seem to deserve more than historical interest. 



In rejecting this mechanical theory Mall traces monstrous 

 development to faulty implantation of the ovum in a diseased 

 uterus, which in turn makes adequate nutrition of the embryo 



3 Cf. :Mall COS) and Jordan ('09). 



