40 MALL. [Vor. XIX. 
his study of anomalies of the central nervous system in young 
human embryos. Fischel describes a case with multiple but 
irregular canal formation, which cannot possibly be viewed 
as a case of arrest of development. His other specimen is 
an embryo 10 mm. long, obtained from a woman who was 
perfectly healthy and aborted for unknown reasons. This 
embryo was apparently normal in every respect, with the 
exception of a well marked dilatation of the cord below just 
opposite the root of the leg. There was histolysis of the cord 
and the embryonic skin just over the hydromyelia, which 
Fischel believes indicates that spina bifida is preceded and 
caused by hydromyelia, that is, he accepts Morgagni’s theory. 
At any rate, the great variety of malformations of the spinal 
cord which are grouped under the name of spina bifida cannot 
all be likened directly to Hertwig’s spina bifida in amphibia, 
although in both there is considerable histolysis. Fischel’s 
specimen, which is a very important one, shows conclusively 
that there is a destruction of tissues in the formation of spina 
bifida much the same as I have noted in the description of 
some of my specimens. In other words, the embryo was 
normal before it developed spina bifida. The relations of 
hydromyelia to spina bifida, and of hydrocephalus to anen- 
cephaly, have been discussed so much since the time of Mor- 
gagni, and my cases, as well as Fischel’s, throw no new light 
upon the subject. Dropsy of the cavities and tissues of the 
body accompanies practically all pathological changes in the 
embryo, and it may be considered an effect just as well as a 
cause in these cases of spina bifida. 
Embryo No. 6 shows an interesting condition in the lower 
part of the spinal cord similar to the first case described by 
Fischel. There is a marked vesicle coming off the cord be- 
tween the motor roots of the two last spinal nerves, as may 
be seen in the illustrations. The lower end of the cord ex- 
tends somewhat beyond the -vesicle. The vertebral column 
ends just above the vesicle and is composed of two cartilages. 
Bardeen'* has shown that the double arrangement of the last 
*Bardeen, Amer. Jour. Anat., IV, 1905. 
