No! Ee] s ORIGIN OF HUMAN MONSTERS. 15 
amniotic bands are rarely found, and when they are present 
they are often attached to the body of the embryo and not 
to the deformed extremity. It seems to me, therefore, that as 
facts accumulate it becomes clearer and clearer that the occa- 
sional amniotic adhesions found are due to the presence of 
the monster and are not causal in nature.® 
Possibly I have devoted too much space to the discussion 
of mechanical theories in teratogenesis. What has been said 
is no doubt acceptable to all embryologists, and my apology 
is due to the fact that the influence of maternal impressions 
upon the offspring is still believed in by so large a number of 
American medical writers of note and that mechanical notions 
regarding embryology are entertained by physicians in general. 
The great embryologists from Harvey onward explained 
the conditions found in monsters as due to an arrest of 
development, for they saw in these distorted individuals con- 
ditions which are normally found in the embryo. The 
embryological theory was first well formulated by J. F. 
Meckel, who explained the beast-like appearance of some 
monsters by the fact that in his development man passes suc- 
cessively through stages found in lower animals. To those 
who have accepted the doctrine of evolution this is all clear, 
but it remains to be shown what are the factors in develop- 
ment, and the effect of changes in the embryo upon the 
growth of the foetus. 
As has been pointed out above, we must divide monsters into 
two groups, those in which the proper conditions to produce 
them are already in the germ (are therefore inherited), and 
those due to certain external influences which act upon 
the egg after it is fertilized. It is obvious that only the 
second group can be considered in any experiments made 
upon the embryo. So, if the pathological ova I have studied 
*Ballantyne says: “The reader may feel (and he is justified in so 
feeling) that, after all, experimental teratogeny has not done much for 
the understanding of the mode of origin of monstrosities, if it has 
weakened a belief in the influence of the amnion.” I may add that this 
argument can be applied to maternal impressions as a cause equally as well. 
