170 FUNCTIONS OF NUTRITION. 



mixture at the above temperature, the quantity of acid increases. 

 Bernard and Bertelot* have shown that in this process the fat is decom- 

 posed into a fatty acid and glycerine. A few decigrammes of neutral 

 fat, emulsified with 20 grammes of fresh pancreatic juice from the dog, 

 and kept at a moderately warm temperature, were almost completely 

 acidified at the end of twenty-four hours, leaving only about one-tenth 

 part of undecomposed fat. The change which occurs when fat is re- 

 placed by a fatty acid and glycerine, is as follows : 



Stearine. Water. Stearic Acid. Glycerine. 



C 67 H m O 6 + 3 (II 2 O) = 054 H 108 O 6 -f C 3 II 8 O 3 



It includes, therefore, a hydration, and cannot take place except in the 

 presence of water. If the experiment be performed with pancreatic 

 juice of normal alkaline reaction, or with alkaline infusions of the 

 pancreas, a portion of the acid set free is saponified by union with the 

 alkaline bases. The chemical change accordingly is the same as that 

 in the saponification of fats by continued boiling with water and an 

 alkali; the ferment of the pancreatic juice, in a short time and at a 

 moderate warmth, taking the place of prolonged ebullition in its influ- 

 ence on the fats. 



According to Wurtz and Hoppe-Seyler, this ferment, unlike the two 

 preceding, is insoluble in glycerine, and is rendered inactive by contact 

 with alcohol. Its action can be studied only in the pancreatic juice, 

 or in watery infusions of the glandular tissue ; and its physical qual- 

 ities and composition are even more imperfectly understood than those 

 of other bodies of the same class. 



Mode of Secretion and Daily Quantity of the Pancreatic Juice. 

 When examined in the living animal by means of a canula introduced 

 into its excretory duct, it is found that the action of the pancreas 

 varies much in activity at different times. In the intervals of diges- 

 tion, or if the process be temporarily arrested from any cause, no fluid 

 whatever is discharged from the canula. When digestion is in progress, 

 the pancreatic juice soon begins to run from the orifice of the tube, at 

 first slowly and in drops. Sometimes the drops follow each other with 

 rapidity for a few moments, after which the discharge is suspended. 

 It then recommences, and continues to exhibit similar fluctuations dur- 

 ing the whole course of the experiment. Its flow, however, is at all 

 times scanty, as compared with that of the gastric juice. We have 

 never been able to collect, in a dog of medium size, more than 75 

 grammes in three hours, and usually the quantity has been much less 

 than this. Colin found a great variation in the animals on which he 

 experimented, the quantity being from two and a half to thirty times 

 as abundant at one period as at another. In the bullock, while rumi- 

 nating, the largest quantity obtained was 342 grammes per hour. 



The entire quantity of pancreatic juice per day cannot therefore be 

 determined with precision, but it is evidently moderate in amount, as 



* Bernard, Lepons de Physiologie Experimentale. Paris, 1856, p. 263. 



