Situation and connections. — Of the three structures termed appendages which arise in a triangular form from the superior angle of the uterus, the Fallopian tube occupies the apex of the triangle, while, at nearly equal distances from it are inserted the ligament of the ovary, and the round ligament ; the for mer posteriorly, and the latter anteriorly. In the natural position of the parts, the tube, viewed from without, appears to spring from the uterine angle with a slight downward curve (fig. 404. e), and then inclining hori zontally forwards and outwards, it describes an irregular semicircle, whose inner side looks backwards towards the ovary (g), which is placed nearly opposite to the centre of its length (figs. 368. and 404.). Such at least are the relative situations which these parts exhibit when spread out equidistantly from each other : although it is probable that during life they are more collapsed and lie closer together,— the anterior wall of the tube then being in apposition with the sides and back of the bladder, while its pos terior wall corresponds, at its centre, with the ovary, the superior border with the small intestine, and the inferior with the fold of peritoneum by which the tube is at tached to the broad ligament. The mouth or abdominal end of the tube is generally directed inwards and backwards, towards the distal extremity of the ovary, in close proxi mity to which it is preserved by means of the tubo-ovarian ligament (figs. 368. n and 401. d).
The fold of peritoneum (fig. 4.04. f ), which connects the tube with the main por tion of the broad ligament resembles a mesentery and serves to convey blood-vessels and nerves, as well as to sustain the tube in its place, and to limit its movements. It constitutes that portion of the broad ligament termed the middle wing. The Fallopian tube occupies the entire upper border of this wine, and receives from it a complete perito neal investment, except along the lower bor der or line of junction of the two surfaces of membrane composing it, at which line the ves sels and nerves enter. Thus the tube resembles an intestine in the mode of its investment, but with this difference, that the peritoneal coat is more loosely applied, especially in young subjects ; N‘ here the convolutions of the tube are more distinctly marked, and lie free within the sheath, which does not follow their windings (fig. 418.).* The tubal mesentery (fig. 404.f) is tri angular, or somewhat falciform in shape. Its narrow pointed end is directed towards the uterus, where the tube has scarcely any' ca pacity for independent motion ; hut as the depth of the mesentery increases outwardly greater freedom of movement is permitted. The greatest breadth of the mesentery is found at a distance of two thirds of its length from the uterine extremity, and here it measures li". From this point a slight narrowing occurs, and the membrane ter minates in an abrupt margin 11" in length, which extends from the lower border of the mouth of the tube to the bulbous extremity of the ovary.
This border, which is thickened by the addition of a layer of mucous membrane de rived from the tnouth of the Fallopian tube, constitutes the tubo-ovarian ligament (Ag.
404, d).
Separate parts and divisions. —The full ex tent of the Fallopian tube cannot be ascer tained until the entire canal, in its interior, has been laid open. The tube which, ex ternally viewed, appears to spring from the superior angle of the uterus, is thus seen to commence by a small orifice, ostium uteriuum, upon the inner surface of the uterus. This orifice conducts to a narrow canal (figs. 40.5. b and 406.) which, after traversing the walls of the organ, and constituting the pars uterina, expands into a gradually widening tube ( fig. 405. r), whose form nearly cor responds with the external configuration of the part. Towards the extremity of this canal, a sudden contraction occurs, consti tuting the external orifice of the tube, ostium abdominale (fig. 404. c). But this does not form the termination of the oviduct, for the latter immediately widens into the trumpet like orifice (infundibulum), whose margin, split up into numerous fringed processes, (fimbrice), (fig,. 404. a a) give to that part the torn and jagged appearance suggestive of the idea that it has been bitten or torn, as expressed in the natne, morsua applied by ancient writers to this part. Each of these parts exhibit peculiarities of struc ture, requiring a special description.
Internal, or uterine orifice, ostiunz uterinum. — This orifice, which ought to be regarded as marking the termination rather than the commencement of the tube, is found at the extremity of a short, funnel-shaped conduit, (fig,. 405. a) which leads from the general cavity of the uterus into the upper and outer angle on either side of that organ. Here, while there is no abrupt line of demarcation to indicate the point of commencement of the canal, the characteristic structure of the uterine mucous membrane gradually' ceases. The peculiar arrangement of its capillary vessels and the orifices of the uterine glands, can no longer be discerned, and a slightly plaited condition of the lining membrane of the canal begins to be distinguishable (fig. 405. b).
At this precise point is found the true uterine orifice of the canal, the diameter of which varies in different subjects, but is rarely of larger size than suffices for the easy pas sage of a common bristle. The true diameter of the tubal cavity at this point is best ex hibited by a transverse section; for when the canal is laid open longitudinally, and its walls are separated as at b, in fig. 405. this portion of the interior of the tube appears to have a greater diameter than it actually possesses when the parts are closed, and in a natural state. In some subjects, however, and in certain conditions of the tube, the uterine orifice may be sufficiently patulous to admit of the passage of a fine probe.