Page:The American Cyclopædia (1879) Volume XIII.djvu/45

PANCREAS 35 sels, between the three portions of the duo- denum, behind the stomach, and on the right of the spleen. It is of an irregular, elongated form, flattened from before backward, the left extremity very thin and prolonged to and some- times beneath the spleen ; the right extremity rounded, resting against the second portion of the duodenum ; the color is grayish white ; the length is about 7 in., width 1, and thickness 1 in., and the weight 3 to 4 oz. ; it is rather smaller in woman. The duct is in the interior, going from left to right, receiving in its course the excretory canal which comes from the lar- ger end, or little pancreas as it is sometimes called; it opens into the duodenum, at the lower part of the second curve, by a special orifice, or one common to it and the bile duct; its arteries come principally from the splenic branch of the coeliac axis, and its nerves from the solar plexus. It closely resembles in struc- ture the salivary glands, like the parotid ; it is made up of clusters of secreting follicles form- Ao. S/ll The Spleen (Spl.) with the splenic artery (Sp. A.). Below this is seen the splenic vein running to help to form the vena portcz ( V. P.). Ao., the aorta ; D., & pillar of the diaphragm ; P. Z>., the pancreatic duct exposed by dissection in the substance of the pancreas ; Dm., the duodenum ; B. Z>., the biliary duct opening with the pancreatic duct at ar ; y, the intestinal vessels. ing the ends of the finely branching divisions of the duct; each cluster, with its vessels, nerves, and connecting areolar tissue, forms a lobule, and the several lobules are held to- gether by the ducts, vessels, and areolar tissue ; its development begins by a budding forth of cells from the intestinal canal. The secretion of the pancreas, called the pancreatic juice, is a colorless, alkaline fluid, possessing a consid- erable degree of viscidity ; it consists of nearly 10 per cent, of solid matters, of which by far the most abundant and important is an organic substance, termed pancreatine, resembling al- burnen in being coagulable by heat, by nitric acid, and by alcohol, but differing from it in being also coagulable by sulphate of magnesia in excvss. The pancreatic juice has been ob- tained in the lower animals by introducing a silver canula into the pancreatic duct, and col- lecting the fluid discharged from its orifice du- ring digestion. Its most remarkable property is that, when brought in contact with oleagi- nous matters, it at once reduces them to a state of emulsion, the fatty substance being broken up into finely divided particles, and held sus- pended in this condition in the animal fluid; this intimate mixture of the oily and albuminoid matters forms a white, opaque, milky liquid, and is known as the chyle ; it is also true that the chyle makes its appearance in the intestines only after the pancreatic juice has had access to the alimentary matters. From these experi- ments there is little doubt that the main office of the pancreatic juice in digestion is to act upon the oleaginous ingredients of the food, and to prepare them for absorption by the emulsifying process. (See CHYLE, and DIGES- TION.) The daily quantity of pancreatic juice secreted and discharged into the intestine is estimated at rather more than half a pound in the dog, and between a pound and a half and two pounds in the human subject; the secre- tion is most abundant at the commencement of and during the digestive process, and the prob- ability is that it is very much dimin- ished, if it does not cease entirely, in the intervals of digestion. The pancreas is liable to hypertrophy, atrophy, soft- ening, induration, inflammation extend- ing from neighboring organs, simple and malignant tumors, fatty degeneration, and calculous growth. That it performs some essential function is evident from its existence in all vertebrates, whether carnivorous or herbivorous, and from its presenting a constant relation to the duo- denum, whatever be the proportions of the alimentary canal or the form of the organ ; it is even found in a rudimentary condition in the invertebrates, and as low as the worms (rotatoria) ; also in the annelids proper, the gasteropod and ce- phalopod mollusks, and in many insects; it exists here as csecal appendages with thick walls, lined with ciliated epithe- lium, and opening into the beginning of the intestine. The pyloric caecal appendages of most osseous fishes have generally been re- garded by anatomists as the analogue of a pancreas; they become more and more nu- merous and complex, from the simple ones in the turbot to the 60 in the salmon with a secreting surface of more than 32 ft. ; in the sturgeon they become united into a glandular organ. In some orders these caeca are ab- sent, as in the sharks and rays, pike, and eel, in which the pancreas has the ordinary glan- dular form. Some authors deny the pancrea- tic nature of these caaca, and maintain that they secrete a fluid only accessory to the true pancreatic secretions. In reptiles the pancreas is always present, often large, and in the higher orders more or less in contact with the spleen. In birds it is larger than in any other class, and it probably performs also the office of salivary glands, which are here wanting; it communi- cates with the intestinal canal by two or three openings ; as a general rule the pancreatic se-