I. HUMAN ANATOMY.
Situation. —The pancreas is so placed that for its display it is necessary to open the ca vity of the great omentum. This may be done either by dividing the gastro-hepatic omentuin and depressing the stomach, or by detaching the gastric layer of the epiploon and turning the stomach up, or by dividing the transverse mesocolon and turning up both transverse colon and stomach. In either of these ways the cavity. of the omentum is opened, and the organs concealing the pancreas are removed.
Placed transversely across the upper part of the abdominal cavity, and closely applied to its posterior wall, the pancreas extends from the duodenal fold on the right to the hilum of the spleen on the left, across, therefore, the epigastrie into both hypochondriac regions. It is not perfectly transverse, however, but ex tends from the right a little upwards as well as to the left ; it corresponds to the level of the first and second lumbar vertebrm and to the splitting of the two laminw of the trans verse mesocolon : it is post-peritoneal, being invested by that membrane only on its an terior surface.
Relations. —By its right extremity it is closely engaged in the curvature of the duo denum, to the inner border of which it is intimately attached, and which it often re ceives into a groove more or less deep, formed by a projection of the gland to a slight extent on the anterior and posterior surface of the intestine. Sometirnes this groove is very slight, and the relation of the margins of the gland and intestine merely that of apposi tion ; at others, the inner margin of the duo denal fold will be deeply imbedded in the gland substance, the projection both in front and behind being considerable. More fre quently, however, the gland trespasses much further behind the intestine than it does in front, so much so occasionally as to separate it in a great degree from its posterior rela tions. The structures on which the posterior surface of the pancreas rests are, the vena cava, the bodies of the vertebrx, the aorta, the crura of the diaphragm, the left kidney, its supra-renal capsule and renal vessels, the lower part of the solar plexus with the com mencement of the plexuses thence pro ceeding,, as the aortic and superior mesenteric ; the splenic vein passing from left to right, the superior mesenteric vein and artery, the vcna portm, the common bile duct, many lym phatic vessels and glands, and the commence ment of the thoracic duct and vena azygos.
To all these structures it is intimately at tached by cellular tissue, and to the irregular surface which they form it is, as it were, moulded or modelled, so that when it is care.
for instance, the longitudinal furrow occupied by the spicnic vein, and the deep groove in fully dissected away, it presents eminences and depressions corresponding to them, as, which the superior mesenteric artery and the vena portm are received.
In front it is in relation with the posterior surface of the stomach, which rests on it when empty (tanquam pulvinar, Scemm.), and moves freely upon it ; but when this organ is distended with food, it recedes from it, and its lesser curvature comes into more immediate relation with the gland. In cases in which the stomach is situated lower down than usual, as in emaciated individuals, where a great part of the small intestine occupies the cavity of the pelvis, the pancreas comes into relation in front either with the liver, or with the anterior wall of the abdomen, from which the gastro-hepatic omentum alone separates it, and through which it may be easily felt. This disturbance of the normal relations al ways exists, according to Cruveilhier, when ever the vertebral column can be felt im mediately behind the walls of the abdomen. The pancreas is also in relation, in front, with the angle formed by the ascending and trans verse colon and with the commencement of the duodenum.
The upper border is in relation with the splenic artery, for the reception of which it is grooved, and which often runs in a canal formed in the substance of the gland through its entire length ; it is in relation also with the Spigelian lobe of the liver, with the first portion of the duodenum, and the cceliac axis.