146 THE DIGESTIVE FLUIDS. 



The secretion of the pancreatic digestive fluid, like that of the 

 saliva, is partly under the control of cerebrospinal nerve-fibres, 

 which are derived from the vagus, and partly of sympathetic fibres. 

 It is noteworthy, however, that even after section of the vagus 

 and the splanchnic nerves pancreatic secretion begins when the acid 

 contents of the stomach reach the duodenum. Bayliss and Starling 

 have shown that this result is due to the activation, by the acid 

 gastric juice, of a hormone present in the mucosa of the duodenum 

 and jejunum which they term prosecretin, with the consequent pro- 

 duction of free secretin. This latter is absorbed into the blood, is 

 carried to the pancreas, and then stimulates the secretion of pancre- 

 atic juice. How the secretion is subsequently maintained, viz., by 

 continued action of secretin or by nerve influences, is not known. 



The material from which the secretion is elaborated through the 

 specific activity of the glandular cells is obtained from the lymph, 

 and ultimately, of course, from the blood. In carnivorous animals, 

 in which the secretion of the pancreas is intermittent and dependent 

 upon the ingestion of food, we accordingly find that in its stage of 

 activity the gland assumes a bright rose color, and is much increased 

 in size, while in the resting stage it is pale and shrunken. 



General Properties. Fresh pancreatic juice is best obtained by 

 tying a cannula directly into the duct or by preparing a permanent 

 fistula according to Pawlow's method, viz., by resecting a small 

 piece of the duodenum (in a dog), where the pancreatic duct opens, 

 suturing the ends into the abdominal wound and making an anasto- 

 mosis between the free ends of the gut. The pancreatic juice which 

 is then obtained represents a clear, colorless, odorless fluid of a 

 strongly alkaline reaction ; it is thick and glairy in some animals 

 and thin and limpid in others. It shows no proteolytic activity 

 whatever, but can be rendered physiologically active by the addition 

 of intestinal juice or an extract of the intestinal mucosa. The acti- 

 vating factor is a peculiar body which has been discovered in the in- 

 testinal juice by Pawlow and his pupils, and which is termed entero- 

 kinase (which see). 



When kept for a few hours at ordinary temperatures it loses its 

 viscosity and transparency, and rapidly undergoes putrefaction. 

 Crystals are then deposited which consist of leucin and tyrosin ; 

 they result from the digestion and subsequent decomposition of con- 

 tained albumins. To prevent these changes the secretion must be 

 placed on ice at once or treated with chloroform-water, toluol, 

 or a similar antiseptic. Owing to the presence of the large 

 amounts of albumin which the pancreatic juice contains, the liquid 

 coagulates to a dense mass when heated to a temperature of 74 C. 

 On cooling to C., or when dropped into water, a clot is formed, 

 which redissolves on warming the solution or on adding an excess of 

 sodium chloride. 



Amount. The amount of pancreatic juice which is secreted in 

 the twenty-four hours is variable, and dependent upon the quantity 

 and quality of the food ingested. In man it varies between 700 and 



