1889.] Evibryology. 647 
the side opposite the mesometrium they are much shorter. These facts 
can probably be explained as a result of the increase in size of 
the embryo, during which it meets with the least resistance at the 
free side of the cornu, the swelling consequendy increasing more 
rapidly on that side, while the axial ends of the glands are drawn 
down from the mesometrium, and those on the free side of the cornu 
During the early stages the axis of the embryo lies transversely to 
the axis of the cornu, but when the uterine cornu reaches a diameter 
of about one and one-eighth inches the embryo changes its position, 
and remains with its axis parallel to the axis of the cornu ; the ven- 
tral side of the embryo is toward the mesometrium. About this 
time the placental band or zone, at a point diametrically opposite the 
mesometrium, undergoes atrophy, which in the last stages almost 
severs the placental girdle as a groove in its inner face. In this 
attempt at a break in the continuity of the placental zone, the cat re- 
sembles the squirrel, in which, as Professor Ryder has shown, so much 
of the zone is atrophied that only a square piece of the original 
placenta remains. 
The blood supply of the maternal portion of the placenta is very 
noticeable at this stage. The sides of the crypts are well supplied 
with very large capillaries, and supported on the inner ends of the 
crypt are large ves.sels carrying maternal blood, forming avascular 
mesh-work through which the crypts open into the uterine cavity. 
The peripheral ends of the uterine glands are not transformed into 
crypts, but seem to form a layer of spongy tissue, the decidua, and it 
is very probable that at parturition a portion of the degenerate epithe- 
lium of the crypts adheres to the muscular walls of the cornu, and re- 
During the growth of the embryo the annular muscular band under- 
goes considerable change. Its fibres are turned from their normal 
direction, and run obliquely over the uterine dilatation. At the end of 
gestation the length of the uterine cornu is about twice that of the 
This study was conducted in the Biological Laboratory of the Uni- 
^•ersity of Pennsylvania, under the direction of Professor Ryder, to 
whom I would express my obligations for the valual'le aid which he 
extended during its pro.secution. — M. J. Gkki.x.max. 
