DIGESTION 



189 



the distal end of the cannula, when it can be collected. According to 

 Bernard, normal juice can be obtained only during the first twenty-four 

 hours of the experiment. The juice obtained from a temporary fistula is 

 clear, slightly opalescent, viscid, of a decidedly alkaline reaction, and has a 

 specific gravity (in the dog) of 1.040. When cooled to oC., it assumes a 

 gelatinous consistence. At iooC. it completely coagulates. When obtained 

 from a permanent fistula, the juice is watery and the solid constituents are 

 very much diminished in amount. 



The chemic composition of the pancreatic juice of the dog as determined 

 by Schmidt is as follows: water, 900.76; organic matter, 90.44; inorganic 

 salts, 8.80. Of the inorganic salts, sodium carbonate is probably the most 

 essential, as it is this salt which gives to the juice its alkaline reaction. 



Human pancreatic juice obtained from a fistula of the duct was found to 

 be clear and limpid, resembling water, alkaline in reaction and with a sp. gr. 

 of 1.007. The total solids of two specimens amounted to about 1.270 and 

 1.244, grams in 100 grams of the juice. The amount of juice collected 

 varied from 420 c.c. to 884 c.c. daily. 



Mode of Secretion. The secretion of the juice is, in the rabbit and 

 dog at least, almost continuous during a period of twenty-four hours after a 

 single average meal, though the rate of flow varies considerably during this 

 period. Shortly after the food enters the stomach the flow of the pancreatic 

 juice begins, and steadily increases in amount until about the third hour, 

 when it reaches its maximum; after this period the flow diminishes until the 

 sixth hour, when it again increases for about an hour. It then gradually 

 diminishes until it ceases entirely. During the period of secretory activity 

 the blood-supply is very much increased, from a dilatation of the blood- 

 vessels. 



The secretion and discharge of the pancreatic juice is associated with 

 the introduction of food into the mouth and stomach and its early passage into 

 the duodenum and is brought about by the action of a primary and a second- 

 ary stimulus. 



The primary stimulus is a psychic state according to Pavlov induced by 

 the sight, odor and taste of food and which leads to the discharge of nerve 

 impulses from nerve-cells in the medulla oblongata and their transmission by 

 efferent nerves in the trunk of the vagus nerve, to the cells of the acini. It is 

 probable that the impressions made by the food on the terminal filaments of 

 the afferent fibers in the vagus nerve develop nerve impulses which, when 

 transmitted to the medulla, occasion the discharge of nerve impulses that not 

 only excite the secretion but increase the blood-supply as well. The vaso- 

 motor nerve impulses reach the blood-vessel supplied to the gland, by 

 way of the great splanchnic nerve and the post-ganglionic fibers from the 

 semilunar ganglion. That the vagus nerve contains secretor fibers for the 

 pancreas has been established by Pavlov. This investigator states indeed 

 that the vagus nerve contains two classes of fibers for the pancreas, secreto- 

 motor and secreto-inhibitor, as well as vaso-dilatator fibers for the blood- 

 vessels, and therefore the effects of stimulation are often contradictory and 

 confused, but if the nerve be divided and time given for the degeneration of 

 the secreto-inhibitor and vaso-dilatator nerves, usually a period of four or 

 five days, then stimulation of the peripheral end of the nerve with induce* 

 electric currents is followed after a latent period of two to three minutes by 



