No. 1.] ORIGIN OF HUMAN MONSTERS. 213 
derm only. The villi and epithelial cells are wanting, but in 
their place there is a thick layer of mother’s blood. The entire 
chorion is lined with an amnion and into its cavity the nodule- 
like embryo projects. Its tissues are not uniform, being thick- 
ened at some points, necrotic at others, and mucoid at others. 
Throughout the center of the nodule there are some capillaries 
filled with blood. At the point of juncture between the amnion 
and chorion there are three projections from the embryo into 
the coelom—(1) the umbilical vescicle; (2) the allantois; and 
(3) the heart. That the second is the allantois is indicated by 
its cavity, which is multiple at points. The heart is within a 
pocket of the ccelom and has an irregular lumen which is well 
Alled with blood. At the base of the nodule there is a short 
tube which communicates with the allantois, the intestine. 
No. 166. 
Ovum, 40 x 40 x 40 mm.; embryo, 2.5 mm. 
Dr. Cassett, Baltimore. 
Last period on October 18. On December 29 there was a 
discharge of blood which continued until the 31st, when the 
mole was expelled. 
The mole is composed of very thick, fleshy walls within 
which there is a cavity with a smooth wall, measuring 30 x 
Fic. 166.—Section through the embryo. X 15 times. Ch, chorion; am, 
amnion; 7, nervous system; 1, heart or umbilical vesicle. 
