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COMPARATIVE ANATOMY OF PANCREAS. 



toneiun. When opened, the innumerable component creca 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 Ziphiaa 

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

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

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

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

 cholcdochus. 



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 (Zygccna malleus), we find an elongated, narrow, 

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



In the Stingray [Trygon sabina), 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 figures represent the position and appearance of the pancreas of 

 the Stingray {Trygon sabina). 



Fig. 12. 



Fid. 10. 



Fia. 12. — Position of the stomach, spleen, ami intestine of tbe Stingray (Trygon sabina) after the removal of the liver. 



Reduced one-half diameter. — A. Inferior portion of the oesophagus expanding into the stomach. 15. Stomach. 



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



mark the turns of the valve. 

 Flo. 13 represents the stomach and spleen of the Trygon sabina 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. I'. Pancreas, presenting the appearance of this organ in the higher 



animals. 



