No. 1.] ORIGIN OF HUMAN MONSTERS. 37 
In this animal the monster lives much longer than the larve 
of frogs and toads do, and for this reason terata with spina 
bifida or anencephaly are obtained that resemble very much 
those found in man. It was found that a .5 per cent solution 
of NaCl produced no perceptible effect on Axolotl, that a 
.6 per cent solution made half of them grow into monsters, 
and in a .7 per cent solution all of them had spina bifida. In 
them it was found that the neural tube did not close regu- 
larly, and often several dorsal openings remained, some until 
the embryos were quite large. In frogs gastrulation was 
affected decidedly by the .6 per cent solution of salt; in 
Axolotl gastrulation remained normal in the .7 per cent solu- 
tion, the change being confined to the brain and cord, but did 
not extend to its caudal end. The exposed cord underwent 
a certain amount of histolysis and cytolysis with more or 
less scar formation, thus resembling very much the condition 
found in spina bifida in man. At the conclusion of Hertwig’s 
paper he rightly asks whether it is not possible for chemical 
substances in the blood, alcohol, toxines or doses of medicine, 
to pass from the uterus to the ovum in man and produce 
monsters. It is clear that he believes that monsters are not 
germinal and hereditary, but that they may be produced from 
every normal ovum through influences in its environment. 
Schaper® has shown us, by producing anencephaly in tad- 
poles by mechanical means, that the rest of the animal grows 
normally without the presence of a brain. In fact, only the 
spinal cord degenerates after the brain has been removed. 
The experiment of Schaper has been further extended by 
Harrison,’ who removed only the spinal cord, leaving the 
brain, before the spinal nerves are formed. In these experi- 
ments also the tadpole grows normally without a spinal cord 
or spinal nerves unless the operation interferes with the devel- 
opment of the lymph-heart, when dropsy follows. Harrison 
produced similar results in embryos in which the action of 
°Schaper, Jour. Bost. Soc. Med. Sci. 1898, and Roux’s Archiv, VI, 
1808. 
"Harrison, Amer. Jour. Anat., III, 1904. 
