4 MALL. [Vou XIX. 
belief is of great antiquity, and is at present of world-wide 
distribution. It also was attacked in the eighteenth century, 
first by Blondel from a philosophical and then by Haller from 
a scientific standpoint. 
All the theories can be resolved into the simple question: 
“Are the conditions which produce a monster germinal and 
therefore hereditary, or are they produced from normal 
germs by external influences?’ The discussion on both sides 
of the question has been a long one, conducted during many 
years by the ablest masters, among whom are always in- 
cluded the leading anatomists of the time. However, the 
theory of external influences gradually gained ground during 
the nineteenth century, as the science of embryology was 
cultivated more and more. But here again we have two 
schools, the one believing that monsters are formed from 
normal germs due to maternal impressions, the other that 
they are due to mechanical influences. It may be noted here 
that the obstetricians and gynecologists of America as a class 
advocate strongly the theory of maternal impressions, due 
largely, no doubt, to their insufficient scientific education. 
On the other hand, we may pride ourselves over the masterful 
strokes of American teratologists against this theory; the 
experimental teratologists have produced double monsters, 
spina bifida and cyclopia, under the very noses of these prac- 
titioners, but they continue their futile speculations over mere 
coincidences. 
With Meckel, who laid the embryological foundation for a 
scientific teratology, and the Saint-Hilaires, who made the 
first teratological experiments, we have the beginning of the 
development of the mechanical theory. It appears in a 
variety of forms, as, for example, that monsters are due to 
tight lacing which causes pressure upon the embryo, or to the 
contracting uterus which naturally might have the same effect. 
However, this theory was gradually transformed by tera- 
tologists so that now it rests upon the idea that amniotic bands 
constrict or compress the embryo, thus bringing about its 
deformity. Occasionally it has been found that monsters are 
