We have spent more time in describing this, the first peritoneal fold we have come to, than is due to its importance, because it affords us, that which we want in this early stage of our description, an instance of the manner in which the peritoneum invests the various organs, having the advantage of extreme simplicity. A bowel is invested by the peritoneum and it occupies a situation in a fold precisely analo gous to that which the round ligament occupies in the falciform ligament; whilst the vessels and nerves of the bowel pass to and from it imbedded in the areolar tissue uniting the ap posed surfaces.
Placing a finger of each hand on each side of the falciform ligament of the liver, they may both be slipped along on the free surface of the anterior parietal portion of the peritoneum in a direction at first upwards, then slanting, then backwards, until they are each of them arrested in a corner, or cul-de-sac. They have passed along first on the peritoneal lining of the an terior abdominal muscles, and afterwards on that of the diaphragm. They are now arrested from being slipped along any further in the same direction by the peritoneum leaping across, or extending across, from the lower sur face of the diaphragm to the upper surface of the liver. In order to pass them along aDy further on the peritoneal surface they must be carried off laterally or slipped downwards over the upper surface of the liver. We will pursue the latter course. The corners, or cul-de-sacs, in which we suppose the fingers to rest, are those formed by the falciform ligament, the liver, the diaphragm, and the coronary liga ment all meeting together : the latter is the name given to that portion of the peritoneum which extends across between the diaphragm and the liver.
First, then, let the finger which is placed on the left side of the falciform ligament be slipped down over the upper surface of the left lobe of the liver, round its anterior edge, and backwards along its inferior surface ; it will be arrested by a membraniform sheet ex tending across from the fissures of the liver to the lesser curve of the stomach, called the lesser or gastro-hepatic omentum. There for the present we leave it, and now let the other finger be in like manner passed down over the upper surface •of the right lobe of the liver, around its anterior surface, and backwards along its under surface, either over the gall-bladder or to the right of it: behind the neck of the gall-bladder, by giving it a direction inclining towards the left, it may be slipped behind the same sheet as arrested the other finger ; that is to say, it may be brought to rest upon the pos terior surface of the lesser omentum, upon whose anterior surface we left the other finger.
This position it gains by being slipped along on the narrow isthmus of liver called lobulus caudatus situated behind the portal fissure, in doing which it passes through a kind of fo ramen, called the foramen of Winslow, whereof the lobulus caudatus is the superior boundary. The inferior boundary of this so-called foramen is formed hy the duodenum ; the posterior by the vena cava; and the anterior by the vena portw, the gall-duct, and the hepatic artery. These are the organs and vessels which sur round the foramen of Winslow : they are, how ever, all covered by peritoneum in such a manner that the finger passed round the fora men, which is about one inch in diameter and of a somewhat semicircular form, glides around on a continuous circle of peritoneum.
The free surface of the lower aspect of the right lobe of the liver has been seen to extend, through the foramen of Winslow, along the lobulus caudatus; the. continuity of surface of course extends to the lobulus Spigelii, from whence it may be traced towards the left and forwards to the posterior aspect of the lesser omentum, and backwards to the posterior abdominal parietes.
The finger being placed on that part of the peritoneum which covers the right kidney, it may be made to glide along the free surface up to the posterior boundary of the foramen of Winslow, and into the foramen itself, which demonstrates the peritoneal continuity in this direction. In much the same way the finger may be slid along on the duodenurn until it is thereby conducted into the foramen.
With regard to the continuity of the perito neal surface of the anterior boundary of the foramen of Winslow, if the finger be placed on the anterior surface of the lesser omentum and slid along on it towards the right, it comes to a free edge thickened by the vessels and duct mentioned above; doubling arouiad this edge it may be made to glide into the foramen ; thus demonstrating that the anterior and poste rior surfaces of the lesser omentum are con tinuous with one another around the vessels and duct that thicken its free border and form the anterior boundary of the foramen of Win slow.