Further analysis of the data leads into a consideration of the anatomy of the viscus in terms of the acceptable theories of the origin of the lesion. It is commonly believed that infection of the gland occurs by passage of organisms through the duct opening in the intestines, especially when there is swelling of the mucosa of both. For the human being the idea is current that infection or obstruction of the common bile duct may spread to the pancreatic duct, and that mechanical or inflammatory obstruction of the papilla of Vater may permit the bile to pass up the pancreatic duct. This theory is based upon certain observations, notably those of Opie, in cases, where a gall stone obstructed the ampulla, bile entered the pancreas and acute pancreatitis arose, partly by the activating action of the bile upon the pancreatic juice and partly by bacteria introduced at the same time. This method of origin is perhaps accepted in most quarters, but there are some who believe that infection of the gland may occur by the infiltration of lymphatics around the pancreas by disease of adjacent parts—gall- bladder, stomach or lymph nodes. Quotation has already been given to reference literature, and I shall not go further into theory except in pointing out how our material may help to answer the question. In the first place it seems perfectly obvious that infection might in any animal travel from the intestine to the pancreas _via_ its ducts, the main question to be settled being the relative importance of the infection _via_ the bile duct. Let us now see if the variations in anatomy will cast any light upon the matter. Among the 1860 mammals, there are as far as I can determine 1275 which have one pancreatic duct opening in conjunction with the bile duct, 585 in which the former has an intestinal opening independent of the latter. Among this 1275 there are nineteen cases of pancreatitis, while among the 585 there are eight cases, or as 14.9 to 13.6. All Aves have separate biliary and pancreatic ducts and relatively little pancreatitis, although frequently suffering with its most common accompaniment, namely duodenitis. There is therefore some evidence that more pancreatitis occurs when there is a physical proximity or combination of bile and pancreatic ducts.