THE FALLOPIAN TUBES. 1125 
often seen slightly projecting and ready to burst. In the deepest part of the ovary the 
blood-vessels are most numerous, and here also some smooth muscle fibres are to be found. 
The ova and other cells that compose the Graafian follicles are derived originally 
from the germinal epithelium which covers the developing ovary in the embryo. The 
epithelium, at first simple, grows down into the underlying tissue in the form of branching 
tube-like processes, or “egg tubes.” This takes place during foetal development, and the 
branching cellular processes so formed become broken up, within the stroma, into little 
nests or clumps of cells, each of which becomes a Graafian follicle. From the beginning 
Downgrowths of epithelinm Ovum with its investing cells : Stratum granulosum 
Germinal epithelium 
ZZ 
ae ee 
/ “| Liquor follieuli 
Nests of epithelial cells Ovarian stroma Graafian follicle Ovum Discus proligerus 
Fic. 771.—A. DIAGRAMMATIC REPRESENTATION OF THE MANNER IN WHICH THE GRAAFIAN FOLLICLES ARISE 
IN THE DEVELOPING OvaRy. B. DIAGRAM ILLUSTRATING THE STRUCTURE OF A RIPE GRAAFIAN 
FOLLICLE. 
some cells of the egg tubes are larger than the others; these become the future 
ova, while the cells round them become the investing cells of the follicle. The investing 
cells, at first flattened, form a layer round each ovum. Later becoming columnar, as the 
follicle increases in size and sinks more deeply in the stroma, these cells divide in such a 
manner that the ovum becomes surrounded by a double layer of cells. Fluid—liquor 
folliculi—accumulates between the two cellular layers, except at one place where the 
inner cells surrounding the ovum remain attached to the outer layer or stratum granu- 
losum. ‘To the inner cellular mass enclosing the ovum (ovulum) the term discus 
proligerus (cumulus oophorus) is applied (Fig. 771). The ripe follicle contains a rela- 
tively large amount of fluid, and the surrounding stroma becomes differentiated to form 
for each a capsule (theca folliculi). This capsule is composed of an inner more vascular 
layer (tunica interna), and an outer more fibrous layer (tunica externa). There is 
reason to believe that in the human embryo the formation of ova and follicles ceases at 
birth, and that the appearances which have led to the belief that they may originate 
during the first years of extrauterine life have been due to pathological conditions. In 
the young child there are enormous numbers of small follicles in the superficial parts of 
the ovary, but in old age none are found in this situation. 
The appearance and structure of the ripe ova have been described on p. 10. 
Vessels and Nerves of the Ovary.—The ovarian arteries, corresponding to the spermatic 
arteries of the male, are a pair of long slender vessels which spring from the anterior aspect of 
the aorta, below the level of origin of the renal vessels. Each gains the pelvis in the fold of 
peritoneum forming the suspensory ligament of the ovary, and enters the ovary at its anterior 
border or hilus. These ovarian arteries anastomose freely near the hilus with other vessels 
derived from the uterine arteries. The blood is returned by a series of communicating veins, 
similar to the pampiniform plexus in the male. The nerves of the ovary are derived chiefly 
from a plexus which accompanies the ovarian artery, and which is continuous above with the renal 
plexus. Other fibres are derived from the lower part of the aortic plexus, and join the plexus 
on the ovarian artery (plexus arteriz ovarice). The lymphatics of the ovary join with those 
from the upper part of the uterus, and end in the lumbar lymphatic glands. 
THE FALLOPIAN TUBES. 
The Fallopian tubes (tube uterine) are a pair of ducts or passages which convey 
the ova, discharged from the Graafian follicles of the ovaries, to the cavity of the 
