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COMPARATIVE ANATOMY OF PANCREAS. 



toneum. When opened, the innumerable component caeca are found to be formed 

 by the successive divisions of the single great duct into which they all pour their 

 secretions into the duodenum immediately below the pyloric valve. 



In the Sturgeon, the structure of the pancreas is similar to that of the Ziphias 

 gladius. The hundreds of ciBca ramified from one common duct are inclosed in a 

 muscular and peritoneal coat. The contraction of the muscular tunic compresses 

 the cfBca and forces their secretion into the intestinal canal. The excretory duct 

 opens close to the pyloric valve and the termination of the ductus communis 

 choledochus. 



In the Eel, Pike, and fresh-water Trout, we find a yellowish-white compact gland- 

 ular pancreas, having from two to three excretory ducts, which are frequently 

 accompanied in their course to the intestine by the biliary ducts. In the Trout 

 and some others there exist both pyloric appendages and a compact pancreatic 

 gland. 



In the Hammerhead Shark [Zygoena malleus), we find an elongated, narrow, 

 flattened, light yellow, compact pancreas, with little lobulation. (See Fig. 22.) 



In the Stingray {Trygon sahma), this organ is of a yellow color, and well defined, 

 lobulated form, resembling in all respects the perfectly-developed pancreas of the 

 Mammalia and other vertebrates. 



The following figufes represent the position and appearance of the pancreas of 

 the Stingray [Trygofl sahina) . 



Fig. 12. — Position of the stomach, spleen, and intestine of the Stingray [Trygon sahina) after the removal of the liver. 

 Reduced one-half diameter. — A. Inferior portion of the oesophagus expanding into the stomach. B. Stomach. 

 S. Spleen. C. Duodenum, or commencement of small intestine. R. Intestine vrith spiral valve; the dark lines 

 mark the turns of the valve. 



Fio. 13 represents the stomach and spleen of the Trygon sahina turned over to one side, thus exposing the pancreas. 

 Reduced one-half diameter. — A. Inferior portion of the oesophagus expanding into the stomach. B. Stomach. C. 

 Small intestine, or duodenum. S. Spleen. P. Pancreas, presenting the appearance of this organ in the higher 

 animals. 



