No. 1.] ORIGIN OF HUMAN MONSTERS. 113 
The other specimen of the fourth week is the remnant of 
the embryo from No. 334. Here the destruction is quite 
complete, only fragments of a four weeks’ embryo being 
found in a small space of a large mole. The piece shows dis- 
sociated organs of an embryo much like No. 285. 
These specimens give the beginning and the end of dis- 
sociated embryos during the fourth week, with an attempt to 
remedy the difficulty in one specimen (No. 336), and the 
almost complete destruction in another (No. 334). It is 
probable that the primary trouble in No. 336 lay in the 
umbilical cord. 
EMBRYOS OF THE FIFTH WEEK. 
The changes in the beginning of the fifth week are quite 
similar to those at the end of the fourth week, for the normal 
development has advanced but very little. However, toward 
the end of the fifth week, when the anlages of the ribs 
appear and there is further differentiation in the mesenchyme, 
we also find modified pathological processes, which are quite 
characteristic, and are not seen in earlier stages. The first 
specimens, then, which are about to be described could also 
with propriety have been considered with those at the end of 
the fourth week. In these we find again the dilated and disso- 
ciated central nervous system, dissociation of the tissues and 
the organs, infiltration of the liver with round cells, and a 
dilated and gorged vascular system. All these changes are 
well marked in Nos. 97 and in 251. In No. 251, however, 
the pathological changes are so marked that it merits a 
special description. The chorion is well enveloped in pus, 
showing that an active endometritis encircled it. The head 
of the embryo is rounded, solid and filled with a dissociated 
brain. The face is practically destroyed and the brain is pro- 
truding on the dorsal side of the head. Following the sections 
_in order down the spinal cord, it is found that in this the 
central canal is distended and the walls partly dissociated. 
