In the class Mammalia there are usually two ducts, one entering the duodenum in combination with the bile duct, the other variously above or below this common opening. As will be seen in Table 14, however, there are several exceptions to this statement, there being but one duct opening independently of the bile duct. The general anatomy is closely similar throughout this class, so I shall confine my notes to the exceptions from the general rule, especially where they seem to be of importance in the etiology of pancreatic lesions. In the class Aves the pancreas consists usually of two or three distinct lobes lying one in front and two behind the cleft between the limbs of the duodenal loop, and it discharges its secretion into the duodenum by two or three ducts separately, and almost invariably above the bile duct openings. One duct always opens near the top of the distal end of the duodenal loop, near the bile duct. In the gallinaceous birds that have a bile duct opening into the duodenum near the pylorus, there is usually a pancreatic duct opening there also. In some birds a third duct passes from the body of the pancreas to the duodenum at different places along the loop. It does not seem probable that dislocation of the duodenal loop would seriously interfere with the passage of the pancreatic secretions, since the gland is so intimately related with the duodenal serosa, but obstruction to the biliary flow due to changes in position of the intestine is easier because the bile duct is separate and loose and arises from the end of the gall-bladder. The ducts of both these structures pass very obliquely through the duodenal wall a matter of importance, as will be seen when discussing the infiltrative forms of enteritis. The gall-bladder is not present in all birds, but this is probably of no importance, as the hepatic ducts are wide and run directly from the liver to the duodenum. The pancreatic ducts are short and are closely bound around by glandular tissue up to a place quite close to their entrance into the intestine. The musculature of the gall-bladder and the ducts seems comparable in mammals and birds, and a constrictor or sphincter usually called the muscle of Oddi, is present in all but pigeons (Oddi). There may be found also muscular fibres in the major ducts of the pancreas, but they are not so heavy nor distributed so definitely as similar tissue in the bile duct walls. The mucosa of the pancreatic duct is much more folded in birds than in mammals, seemingly, therefore, more adapted to obstruction by swelling from any cause.