376 MINOT. [VoL. II. 
§ 11. Summary.!— In the resting uterus of the rabbit there 
are six longitudinal folds. The ovum attaches itself on or 
between the two folds nearest the mesentery, and the placenta 
is there developed ; the two adjacent lateral folds form a cushion 
(the peri-placenta) about the placenta, but the two folds oppo- 
site the mesentery are flattened out by the stretching of the 
walls to form the swelling to contain the embryo; they consti- 
tute the ob-placenta. In the region of the placenta the mucosa 
undergoes an enormous hypertrophy: there is likewise an 
enlargement, but much slighter, of the peri-placenta. 
The entire epithelium lining the uterine swelling degener- 
ates; its nuclei proliferate, and its protoplasm hypertrophies, 
becoming at the same time hyaline and granular. The degen- 
eration affects the glands also. The degenerated epithelium 
becomes vacuolated and in large part resorbed. The process 
goes on with distinctive features in each of the three primary 
divisions of the swellings. 
The connective tissue increases by hyperplasia in the peri-pla- 
centa and to a still greater degree in the placenta, and is trans- 
formed for the most part into uninucleate perivascular decidual 
cells, but also in part, — namely, immediately below the glandular 
layer of the placenta, —into large multinucleate cells. In the 
placenta, and to a less extent in the peri-placenta, there is a new 
formation of blood-vessels, which subsequently enlarge to great 
size, although their only walls are an endothelium which under- 
goes rapid hypertrophic degeneration. 
In the placental region the uterine epithelium degenerates 
and disappears, but the glands are preserved as irregular anasto- 
mosing rows of coarse granular matter, with numerous vacuoles 
and scattered nuclei, but without central lumina. Below the 
glands is a zone containing wide vessels and large multinucleate 
cells. The outer layer has wide blood-vessels, with numerous 
uninucleate decidual cells, which arise from the connective tissue 
cells and arrange themselves in successive coats around the 
blood-vessels until they occupy the entire room between the 
vessels. 
The embryo is attached at first to the surface of the placenta 
1 It will be remembered that the observations cover the period of from six to fif- 
teen days ony, and do not include the eleventh day, when several important develop- 
ments occur. 
