OCR Text |
Show 196 DR. R. W. SHUFELDT ON [Apr. I, The Gall-bladder, is of a pear-shaped form and of comparatively large size. Its position has already been given above. Its own duct (cystic) passes down to the duodenum, being joined in mid-course by a biliary duct coming from the right lobe of the liver. Smaller ducts pass from it to enter the right hepatic lobe just mentioned, while upon its surface several minor branches seem to anastomose with each other. In addition to all these we make out an hepatic duct proper; this issues also from the right lobe of the liver, and passing down joins at mid-course the pancreatic duct. A branch joins also this hepatic duct with the gall-biadder. It was a long time before I could bring myself to believe that these several branching ducts were not anastomosing vessels borne in the peritoneum overlying the parts under consideration. I am now, however, fairly well satisfied, after the most careful examination that I could make, that the arrangement is as I have given it. According to Beddard a somewhat similar condition of affairs is to be found in Varanus salvator (P. Z. S. 1888, p. 105, fig. 4). The structure is one that requires and will repay more extended and careful research, and to this end I should very much like to examine large living specimens of Heloderma, and if possible compare them with more specimens of Varanus salvator. The Pancreas.-This organ is of proportionately good size in the reptile before us, and it is to be sought, as usual, in the loop of the duodenum. From its ventral aspect there arises an elongated papilla, and it is at the extremity of this that there enters the single hepatic duct formed by the two smaller ones which emerge from the sulcus in the right lobe of the liver ; while lower down one of these latter appears to send a branch to the duodenum. For its middle third, one of these ducts exhibits a peculiar reddish enlargement, of no great size; I am at a loss to know whether this be normal or not. This enlargement is strung along on the duct for a distance of a centimetre or more, and has the appearance of a very narrow elongated gland through which the duct must pass before arriving at the pancreatic gland. From the apex of the pancreas the common duct, here very short, enters the gut. Peculiar as this arrangement of the cystic, hepatic, pancreatic, and common ducts in Heloderma is, it is not without parallel among Vertebrates, for the arrangement is simulated in the Frog, where, too, a system of branching hepatic ducts coming from the liver unite to form a single duct that passes into the substance of the pancreas, where it eventually unites with the common bile-duct on its way to the duodenum1. In Heloderma the hepatic veins emerge from the liver at its anterior part and soon enter the postcaval vein, as the latter passes forwards to the right side of the heart. 1 For a good drawing of these structures in the Frog, see Wiedersheira's ' Comparative Anatomy of Vertebrates,' translated by W . Newton Parker, 1880, P- 241, fig. 197. Compare also what Sir Eichard Owen has to say upon this point in his ' Comparative Anatomy and Physiology of Vertebrates' vol i pp. 448-454. |