No. 1.] ORIGIN OF HUMAN MONSTERS. 117 
of this stage, and similar to those found in No. 135. These 
changes are given as examples of further development of 
some of the tissues after the general growth of the embryo 
has come to an end. In No. 343 the fore-brain is destroyed 
entirely and the medulla is distended. The outlines of the 
organs and tissues are well defined, and they are fairly well 
infiltrated with migrating blood cells. 
The structure and form of the organs in No. 343 resemble 
in many respects the state of things found in Nos. 330a and 
330b. These two specimens came from twin ova which were 
aborted 128 days after the beginning of the last menstrual 
period, thus making the duration of the pathological process 
fully nine weeks. The chorions are both fibrous, are envel- 
cped in pus and infiltrated with leucocytes. Both embryos 
show practically the same changes in them as are found in 
several other. sets of twins, which seems to me to be strong 
evidence in favor of the theory that the deformed embryos 
are due to endometritis. The changes in both embryos are 
very much alike and can be described together. The epi- 
dermis is intact, but the true skin is hypertrophied, and in 
front of the head, in the region of the deformed mouth, the 
epidermis shows peculiar thickenings. Both spinal cords are 
dilated and their walls are dissociated. The cerebral vesicles 
and mid-brain are nearly destroyed, the main portion of the 
head being taken up by the hind-brain. The large blood- 
vessels and the heart are filled with blood; in 330b the wall of 
the ventricle is infiltrated with blood cells and in 330a it is 
nearly destroyed by them. The tissues and organs of the 
embryos are well dissociated and more or less filled with 
round cells. Some of the liver tissue is necrotic. 
In reviewing the most marked peculiarities of the path- 
ological changes in embryos of the fifth week, it may be noted 
that the differentiation of the tissues has made some of them 
more resistant than others; the more central tissues show the 
least amount of change, and the extremities, head and face 
the most, these giving way first. The spinal cord and 
medulla show more resistance than the brain and do not dis- 
