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AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



the ingestion of food, its quantity, etc., the reader is referred to the section on 

 Secretion. Most of our exact knowledge of the properties of the pancreatic 

 secretion has been obtained either from experiments upon lower animals, 

 especially the dog and the rabbit, in which it is possible to establish a pan- 

 creatic fistula and to collect the normal juice, or from experiments with arti- 

 ficial pancreatic juice prepared from extracts of the gland. Various methods 

 have been used in making pancreatic fistulas : usually the main duct of the 

 gland, which in the two animals named is separate from the bile-duct, is 

 exposed and a canula is inserted. A better method, devised by Heidenhain, 

 consists in .cutting out the piece of duodenum into which the main duct opens 

 and sewing this isolated piece to the abdominal wall so as to make a permanent 

 fistula, the continuity of the intestinal tract in this case being re-established, 

 of course, by sutures. A simple method of obtaining normal pancreatic juice 

 from the rabbit is described by Ratchford. 1 In his method the portion of 

 the duodenum into which the main duct opens is resected and cut open along 

 the border opposite to the mesenteric attachment. The mouth of the duct is 

 seen as a small papilla projecting from the surface of the mucous membrane. 

 Through the papilla a small glass canula may be passed into the duct, and the 

 secretion, which flows slowly, may be collected for several hours. The total 

 quantity obtainable by this means from a rabbit is small, but it is sufficient 

 for the demonstration of some of the important properties of pancreatic juice, 

 especially its action upon fats. As obtained by these methods, the secretion 

 is found to be a clear, colorless, alkaline liquid. The secretion obtained 

 from dogs is thick and glairy, and forms a coagulum upon standing, 

 while that from rabbits is a thin, perfectly colorless liquid which does not form 

 a clot. In dogs the secretion from a permanent fistula soon becomes thinner 

 than it was when the fistula was first established, and this change in its con- 

 sistency is accompanied by a corresponding variation in specific gravity. The 

 specific gravity (dog) of the juice from a temporary fistula is given at 1030 ; 

 from a permanent fistula, at 1010 to 1011. The secretion coagulates upon 

 being heated, owing to the proteids held in solution, and it undergoes putre- 

 faction very quickly, so that it cannot be kept for any length of time. The 

 analysis of the secretion most frequently quoted is that given by C. Schmidt, 

 as follows : 



Pancreatic Juice (Dog). 



Constituents. 



\ \V;iter 



"/Solids 



Organic substances 



Asli 



Sodium carbonate 



Sodium chloride 



Calcium, magnesium, and sodium phosphates 



The composition of normal human pancreatic juice has not been determined 

 completely, owing to the rarity of opportunities of obtaining the secretion, 

 1 American Journal of Physiolntji/, lsii'.i. vol. ii. j>. -is.",. 



