86 
OVARIAN PREGNANCY 
cells enclosed in the meshes of the innermost layer of connective tissue 
(theca interna). These are clearly the progenitors of the lutein cells of 
the corpus luteum, and in a perfectly ripe follicle the layer has developed 
into a zone of considerable thickness. At either of these stages, a distinct 
basement membrane can, in favourable preparations, be made out between 
the young lutein tissue and the membrana granulosa. On the outer side 
of the lutein layer there are numerous vessels, and as the follicle is about 
to rupture vessels appear on its inner aspect also. When rupture takes 
place the greater part of the membrana granulosa is probably shed with 
the ovum, but shreds of it remain within the follicle, more or less detached 
from the theca interna. Haemorrhage and serous exudation now take place 
into the cavity of the follicle, and it becomes occupied by a mass of 
coagulum, consisting; of a delicate fibrinous reticulum and blood clot in 
varying proportions. The lutein tissue now develops with great rapidity 
into a thick layer, the blood-vessels both within and without this layer 
enlarge, and the coagulum is invaded by numerous leucocytes, fibroblasts, 
and young blood-vessels. The point of rupture on the surface of the 
ovary is recognisable for a long period, but communication with the cavity 
of the follicle is frequently, if not always, closed by the formation of 
young connective tissue internal to, or between the lips of the torn lutein 
layer. Data as to the rapidity with which this occurs are wanting, for 
owing to the fact that ovulation and menstruation do not necessarily 
coincide, the date of last menstruation cannot be taken as a point from 
which to estimate the age of an ordinary corpus luteum. Taking however 
the analogy of a healing wound, there would be a thin layer of vascular 
connective tissue between the lutein tissue and the contents of the follicle 
within seven days. If we now apply these data to the matter in hand, 
it will be seen that there are two possible situations in which an ovum 
impregnated within the Graafian follicle may become imbedded. 
There is very good reason for believing, from the data provided by 
the early ovum described in the first paper, that imbedding commences 
while the ovum is still a very minute object, little if any larger than the 
mature unfertilized ovum, that is about *2 mm. Such a minute body 
might readily find a suitable nidus in the thin layer of young connective 
