Numerous and somewhat discrepant views have at different times been advanced regarding the functions of this fluid; we nail here only notice those functions which are connected with digestion. One use that has been ascribed to it, is to neutralize in the small intestine the acid chyme which emerges from the stomach. But the bile can contribute little or nothing to the neutralization of the free acid, because, in the first place, the bile is very slightly alkaline, and often perfectly neutral; and secondly, be cause the thyme in the intestime is still acid after the admixture of the bile. Again, the bile has been asserted to possess a special solvent action on the chyme; but none of the ordinary constituents of the latter seem to he essentially changed, even when digested for a long time with fresh bile. Again, much importance has been attached to the anti septic action of the bile on the contents of the intestinal canal, in favor of which view it is alleged that when no bile is poured into the intestine, the freces have a putrid odor, as is sometimes observed in patients with jaundice, and aswas noticed by Frerichs in animals in which the ductus choledochus had been tied. Another use that has been assigned to the bile is, that it exerts a stimulating action on the intestinal walls, and thus acts as a natural purgative; and in support of this view, it may be mentioned that jaundice (in which the bile does not flow into the intestine) is often accompanied by ex treme constipation, and that purified ox-gall, taken either in the form of pill or enema, produces an undoubted purgative action. But the main use of the bile seems to be to promote the digestion of fatty matters, and it accomplishes this end not so much by any solvent chemical action on the fats (which' at most is extremely slight), as by a peculiar physical action both on the fats and on the intestinal walls, disintegrating the former, and impressing on the latter (by moistening the villi)a peculiar condition which singularly facilitates the absorption of fatty matters. This view is fully confirmed both by direct experiments out of the body, and by comparing the relative qualities of fat that are retained in the body and applied to the purposes of life by animals with biliary fistulous openings, and by healthy animals.
The pancreatic fluid which is poured into the duodenum at the same spot with the bile (see fig. 1), is a colorless, clear, somewhat viscid and ropy fluid, devoid of any special odor, and exhibiting a strong alkaline reaction. This fluid, as yielded by differ ent dogs with permanent fistulous openings, varies considerably in chemical composi tion; the collective solid constituents ranging from 1.5 to 2.3 per cent, the organic matters from 0.9 to 1.6, and the mineral matters from 0.62 to 0.75.
The most abundant and important of the solid constituents is a peculiar substance termed pancreatine, or pancreatic diastase or • ferment, in combination with soda, to which this fluid owes its principal chemical and physiological properties. Calculating from the quantity of pancreatic juice secreted by dogs of known weight, we may infer that it man weighing ten stone secretes daily about ten ounces of this fluid.
One of the chief uses of the pancreatic juice in relation to digestion, is to convert into sugar the amylaceous or starchy matte which have escaped the action of the saliva, and have passed unchanged into the duodenum. It possesses this property in a far higher degree than the saliva; and, as might he expected in reference to this use, the pancreas is found to be much more developed in herbivorous than in carnivorous animals. Bernard, the representative of the modern school of physiology in France, claims for this fluid another important function; he believes that he has proved that it is solely by the action of this secretion that the fat is reduced to a condition in which it can be absorbed and digested; that is to say, that it is decomposed into glycerine and a fatty acid. See FATS. This view. has, however, not been generally accepted, and it seems probable that although the change described by Bernard takes place when fat and pancreatic'jnice tire simply rnixdoi. together iu a•test4ttbe, it does not actually take place in the intestine, the acid gastric juice probably acting as an interfering agent. An attempt has lately been made by Corvisart and Meissner to prove that, like the gastric juice, this fluid can dissolve albuminous matters; but this view cannot be substantiated. Considering the large quantity of pancreatic fluid which is yielded in 24 hours, Schmidt, who has made the digestive juices the subject of his special study, is of opinion that the function of this fluid is not so much to promote the conversion of starch into sugar, as for the purpose of diluting the chyme, and for reconverting the soda (which in the pancreas has been separated from the chlorine of the chloride of sodium, and has combined with the pancreatine) into chloride of sodium. He shows, from numerical calculations, that. more than half of the chloride of sodium existing in the blood which circulates through the pancreas, is broken up into hydrochloric acid and soda, of which the former is separated by the gastric glands, while the latter unites with the pancreatine. Meeting again in the duodenum, the hydrochloric acid and the soda reunite, and re-form chloride of sodium, which is again absorbed, and re-enters the circulation. This is perhaps one of the most singular decompositions and reunions occurring in the animal body.
Of the last of the fluids poured into the intestine, and co-operating in the digestive process, the intestinal juice, we know comparatively little. It is the aggregate secretion of the various glands which we have described as occurring in the walls of the small intestine. It is a colorless, or sometimes yellowish, ropy, viscid fluid, which is inva riably alkaline. We are not aware of any special or characteristic constituent in it, such as occurs in the other chylopoietic fluids. Its daily quantity is probably nine or ten ounces. It seems to unite in itself the properties of the pancreatic and gas tric juices; that is to say, it resembles the former in converting starch into sugar, and the latter in dissolving flesh and other albuminous bodies.