THE PANCREATIC JUICE. 541 



Besides being engaged in the formation of biliary substances, partly 

 intended for use in the digestive process, and partly destined, as we 

 shall hereafter explain, to be thrown out of the body as excrementi- 

 tious matters, the liver has recently been discovered to perform an- 

 other most remarkable office in the economy, viz., that of separating 

 from the blood by its cells, a substance named glycogen, or animal 

 starch, which has the property of being rapidly transformed into glu- 

 cose, or grape sugar. This sugar is supposed to enter the hepatic 

 blood, to proceed with it to the heart, and thence to -the lungs, to be 

 oxidized in the respiratory process, and aid in the development of 

 heat. This glycogenic or sugar-forming function of the liver, will be 

 more fully noticed in the section on Secretion. 



Sources and Composition of the Pancreatic Juice. 



The pancreas (nav xplas, all flesh), or abdominal sweetbread, is a 

 long, narrow, pinkish gland, flattened before and behind, having its 

 right, larger end, lodged in the concavity of the duodenum; whilst its 

 left, pointed extremity, touches the spleen. Its shape has been com- 

 pared to that of a dog's tongue, or of a hammer. It crosses over the 

 front of the first lumbar vertebra, behind the lower border of the 

 stomach, and is held in place by its attachment to the duodenum, by 

 its bloodvessels, nerves, lymphatics, and ducts, by areolar tissue, con- 

 necting it with adjacent parts, and by a peritoneal layer. It is about 

 6 or 8 inches long, 1J inch broad, and from \ an inch to 1 inch thick, 

 being thicker at its larger end. It usually weighs between 2J and 3J 

 oz., but sometimes as much as 6 oz. 



In structure, the pancreas resembles the salivary glands, and has 

 been termed the abdominal salivary gland. Its numerous lobes and 

 lobules are compressed, and are held together by the vessels, ducts, 

 and interlobular areolar tissue. Each lobule, like those of the parotid 

 gland, Fig. 42, c, consists of a branched duct, ending in rounded ves- 

 icles, surrounded by networks of capillaries. The ducts, from the 

 numerous lobes, join a principal duct, which runs through the gland 

 from left to right. This duct, the pancreatic duct, or canal of Wir- 

 sung, who discovered it in the human body, in 1642, is about the size 

 of a small quill ; it emerges from the larger end of the gland, and, 

 accompanied by the common bile duct, passes, with it, obliquely 

 through the walls of the duodenum, and, about 3 inches below the 

 pylorus, opens into the intestine by a common orifice with the bile 

 duct, or sometimes by a separate aperture. Occasionally there exists 

 a supplementary pancreatic duct, which enters the duodenum about an 

 inch from the chief duct. 



The secretion from the pancreas, or the pancreatic juice, is a some- 

 what viscid, transparent, colorless, and inodorous fluid. The quantity 

 secreted daily, in animals, varies, according to different observers, from 

 15 to 35 grains per hour for each pound weight of the body; so that 

 in a man weighing 140 pounds, the quantity secreted would, be from 

 4| oz. to 11 oz. per hour. The secretion is probably not continuous, 



