The splenic omentum is the name given to that long corner of the great omental pouch which extends up to the left of the fundus of the stomach as high as the cardia. It obtains its name from the circumstance of the spleen being situated on its outer aspect. The spleen, in a certain sense, is included between the layers ; it is invested, however, by the outer layer alone,—the inner layer passes by it un interruptedly. Soemmering rnentions a liga mentuta phrenico-gastricam, a peritoneal fold connecting the cardiac end of the stomach to the diaphragm ; it is the very uppermost corner of this part of the great omental sac, which gets somewhat behind the cardia, and is not unfrequently complicated by one or two small falciform folds, rendered very conspicuous by pulling up the stomach. The attachments of this part of the great omental pouch have already been described ; between its layers are contained, at its very tip or uppermost corner, the arteria coronaria ventriculi, with its accom panying vein and nerves ;* and lower down the splemc vessels and nerves as far as from the parietes to the spleen, and the branches of the splenic vessels called vasa brevia and gastro epiploica sinistra, as far as to the fundus of the stomach. There are a few lymphatic glands near the root of the spleen ; such glands, together with fat in variable quantities, are very commonly included between the layers of the peritoneal duplicatures. The use of the sple nic omentum is to retain the spleen and stomach in situ, and to give transit to the splenic and gastric vessels.
The great omentum, called also the gastro colic omentum. The apron-like appearance and the sac-like form of this singular structure, and also its attachments, have been described above; it is necessary to add the following remarks. It extends much further down in the adult than in the fcetus. It reaches lower down on the left side than on the right. Owing to the proximity of its lower edge to the femoral and inguinal rings, it frequently constitutes a part or the whole of the contents of hernial sacs. It reaches lowest down when the stomach is empty, and is very considerably drawn up by distension of that organ. It is usually spread apron-like evenly over the small intestines, but is not unfrequently found lying folded up on one side or the other of the abdomen, occasionally even turned up over the liver and stomach. It is frequently loaded with immense quantities of fat, and indeed is seldom or never destitute of it along the sides of the vessels which form such a beautiful net-work between its layers. In the intervals or meshes of this network the omentum is so extremely thin that it is difficult to believe it composed of two layers, and not unfrequently the membrane is deficient in these situations, giving to the whole the appearance of a piece of lace finely perforated. This is always the condition of the great omentum of the dog, in which animal we have repeatedly assured our selves, by using great care in manipulation, that it is not the result of violence; it exists also in the mesenteries of same animals.
The arteries that ramify in the great omen tum are branches of the gastro-epiploica dextra and sinistra, and some anastomosing ones from the colica media which pass round the colon and enter the omentum on the side of the in testine opposite to that on which the artery reaches it. Veins and doubtless nerves accom pany these arteries, and there are some lym phatic glands enclosed between the layers of the great omentutn along the greater curvature of the stomach.
The use of the great omentum has never been satisfactorily pointed out. It is peculiar to, and universal in, the class Alammalia, and therefore always co-exists with a diaphragm ; probably it has some reference to the incessant motion and constantly recurring compression to which the intestines are subject from the action of that muscle in respiration. It is frequently seen dipping very deeply between the convo lutions of the intestines, and occupying their interspaces as a moveable packing material, as if thereby enabling them to retain their cylindrical form whilst subject to incessant disturbance.
The great omentum, being continuous as one sheet with the splenic omentum, may be re garded as a great pouch or widening of the mesentery of the stomach. In those animals, such as the Carnivora, which have a very short colon, the great omentum does not extend from the stomach to the colon, but from the stomach to the pancreas, or to a transverse line of attach ment corresponding in position with that of the transverse part of the duodenum in the human subject. The large intestine in these animals crosses over the small intestine at a point very near the termination of the latter in the ccecum, that is to say, over the lovver part of the ileum, where it usually has a proper mesentery.* The annexed drawing represents the abdo minal viscera of a lizard. There is a prepa ration, showing the same parts of a lizard, in the Hunterian collection, (No. 444 D, Phy siological Series.) The whole of the intestines of this animal, from the cesophagus to the rectum, are connected to the posterior abdo minal parietes by one continuous mesentery attached along the mesial line. In the sheet situated anterior to the stomach, connecting that organ to the liver and enclosing the gall duct in its free edge, we recognise the lesser omentum in what we heretofore considered its typical position. In that part of the mesentery which connects the upper part of the stomach to the posterior parietes we recognise the sple netic omentum ; the spleen is seen enclosed between its layers—apparently a large mesen teric gland. That part of the common mesen tery which, immediately succeeding the last mentioned, connects the middle and lower part of the stomach to the parietes, we cannot help regarding as the great omentum (the pancreas is just below this). Now pouch out this part towards the left, and a great omentum, such as is found in the Carnivora, is produced, with the same relation of other parts, except in the obli quity of the parietal attachment in the last named animals, which is but slight. We have but to enclose the transverse colon between the layers of this sac, to obliterate that portion of the mesentery which is connected to the pan creas and duodenum, and to carry the trans verse portion of the latter across just in the line of parietal attachment, in order to produce the condition of the parts which exists in man. It will readily be perceived how, in the mean time, a foramen of Winslow will have been formed by this imaginary manipulation.* We should deem this pouching or widening of the gastric mesentery to have reference to the great distention to which the stomach is liable, but that the sac is far too ample to be obliterated by. any possible distention of that organ.