No. 1.] ORIGIN OF HUMAN MONSTERS. 93 
not show any signs of endometritis, but since then nearly all 
of the specimens collected have been hardened in formalin in- 
stead of being first washed in water or in weak alcohol, as 
uninstructed physicians do so frequently. Further observa- 
tion with well preserved specimens will also probably show 
signs of endometritis in specimens of this group, less than 
30 mm. in diameter. 
The embryo is entirely destroyed, leaving only the amnion 
in a very small per cent of pathological ova. Usually the 
embryo continues to grow slowly in an irregular fashion, but 
sometimes there is a destruction of some of its parts. In 
most of these cases, however, the circulation has been estab- 
lished and the ccelom is pretty well obliterated, thus elimi- 
nating the importance of the magma reticulé. Therefore 
primary changes in the embryo are clearly associated with 
the blood and the vascular system, and this naturally affects 
the embryo more than it does the other structures. 
I shall consider No. 37 first, because it still contains the 
outline of a portion of the embryo. The atrophic head of 
the embryo is seated upon a very small cord and these are 
surrounded by the amnion. The umbilical vesicle is attached 
to the side of the cord, but does not reach into the embryo. 
The central nervous system is very rudimentary, and the 
heart, liver, myotomes and lower end of the body are wanting. 
The lower jaw is still recognizable, and from it two arteries 
pass over into the cord. The single vein of the cord ends 
blindly just below the rudimentary branchial arch. The size 
and degree of development of the embryo places it in the 
beginning of the third week, when no doubt its destruction 
began. The chorion, however, belongs with those of the 
fourth or fifth week, which indicates that the process of 
atrophy has been under way for a week or two. 
In specimen No. 130 the embryo is reduced to a small 
mass of round cells showing no structure whatever. The 
umbilical cord is filled with its usual blood-vessels, showing 
that an embryo had been present at an earlier date. The 
whole is inclosed in a relatively small amnion, which no 
