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Show 1018 MR. L. R. CRAWSIIAY ON THE ARTERIAL [Dec. 11, A. gastrica dextra.-A varying number of vessels were given off from this artery to the pancreas and adjacent structures as follows:-In Bufo boreas one, some distance beyond the-4. hepatica; in B. mauritanicus one, from near the stomach; in R. hexadactyla one; in R. esculenta two, opposite the origin of the hepatica ; in R. clamata (two specimens) one, in the same position ; in R. tigrina two. (In addition to these vessels, the pancreas also received a single vessel from before the origin of the liepatica in R. esculenta, R. hexadactyla, and R. tigrina.) The specimen of R. catesbiana (text-fig. 146, p. 1017) was remarkable for the fact that after the separation of the gastrica sinistra, three arteries were shortly given off to the pancreas and then the remainder of the A. codiaca went to the liver and gall-bladder, the gastrica dextra being entirely absent. It is conceivable that this abnormality might be correlated with the anastomosis which so frequently occurs on the right side of the pylorus between the normally present gastrica dextra and the duodenal branch of the mesenterica. In this case, moreover, the latter artery was continued without diminishing in size over the pylorus and up the right side of the stomach; in fact over the region which the A. gastrica dextra would normally traverse. In this individual, a male, which was sent to me alive from America, the constricted pyloric region was extremely long. In another, a large female of the same species which was examined for comparison, the condition of the arteries here was quite normal, and in this latter case the constricted pyloric region was very short. In the other species, the A . gastrica dextra was continued as a rather larger vessel than the A. hepatica to the right side of the stomach and towards its more distal portion. In three individuals of R. temporaria it only varied in the relative points of its division. It divided into two branches at about two-thirds of the way to the stomach, and each branch again divided into two near the latter. In R. esculenta, the first division of the A. gastrica dextra took place closer to the stomach and the posterior branch was continued as a compact vessel down to the pylorus. In R. tigrina, it began to divide about halfway to the stomach, which it reached in three or four branches. In R. clamata and R. hexadactyla, it divided into an anterior and posterior branch on or near the surface of the stomach (text-fig. 145, p. 1015 ; text-fig. 147, p. 1019). Bufo mauritanicus somewhat resembled R. tigrina, but the subdivision of the artery was more distal. B. boreas was very distinct from the rest by the simultaneous division of the artery close to the stomach into five equal-sized branches, the posterior branch running back as usual to the pylorus, the others breaking up at short intervals in front of it (text-fig. 153, p. 1029). .4. mesenterica anterior.-The extent of variation in this artery is so great that it is difficult to draw more than very general comparisons between the species under consideration. |
