Fig. 182 shows the stomach, left kidney, spleen and splenic flexure of the colon hardened in situ and removed from the body of a two-year-old child. The great omentum has been divided along the line of adherence to the transverse colon.
[Illustration: FIG. 182.--Part of the abdominal viscera of child, two years old, hardened _in situ_ and removed from body. The great omentum has been detached along the line of the transverse colon. (Columbia University, Study Collection.)]
[Illustration: FIG. 183.--The same preparation with the spleen removed, showing lines of peritoneal reflection on mesial surface of the organ.]
In Fig. 183 the spleen has been removed from the preparation by division of its peritoneal and vascular connections, and is shown in its mesal aspect (gastric and renal surfaces, intermediate margin and hilum). It will be seen that the peritoneal reflections are arranged in the form of two concentric elliptical lines. The two ventral lines form the gastro-splenic omentum and correspond to the reflection of the peritoneum from spleen to left end of stomach carrying the gastric branches derived from the splenic artery. The third line from before backwards results from the division of the secondary parietal peritoneum of the lesser sac, covering splenic artery, and ventral surface of pancreas and derived from the dorsal mesogastrium; while the most dorsal fourth line represents the divided reflection of the peritoneum from the renal surface of spleen to lateral border of left kidney and diaphragm (lig. lieno-renale).
Between the second and third lines of peritoneal reflection appears the portion of the mesal surface of the spleen in contact with and invested by the extreme left end of the lesser peritoneal sac.
Fig. 184, taken from an adult human subject with the viscera hardened in situ, shows the left or splenic extension of the lesser peritoneal cavity.
[Illustration: FIG. 184.--Upper abdominal viscera of adult human subject, hardened _in situ_, with liver and colon removed and stomach turned up. (Columbia University, Study Collection.)]
=2. Development of the Pancreas.=--The pancreatic gland is derived from the hypoblast of the enteric tube. The secreting epithelium and that lining the ducts of the adult gland is formed by budding and proliferation of the intestinal epithelium. The gland develops primarily from two outgrowths which are at first separate and distinct from each other.