CHAP, i.] DIGESTION. 251 



Bernard found that with permanent fistulae the secretion altered in 

 nature, and lost many of its characteristic properties. Others, however, 

 have succeeded in obtaining permanent fistulse without any impairment 

 of the secretion. 



Healthy pancreatic juice is a clear viscid fluid, frothing when 

 shaken. It has a very decided alkaline reaction, and contains few 

 or no structural constituents, 



The average amount of solids in the pancreatic juice of the dog 

 when obtained from a temporary fistula is about 8 to 10 p. c. ; but 

 in the thoroughly active secretion from a permanent fistula it is 

 not more than about 2 to 5 p. c., *8 being inorganic matter, 

 and this is probably the normal amount. The important con- 

 stituents are albumin, a peculiar form of casein or alkali-albumin, 

 (precipitable by saturation with magnesium sulphate) peptone, 

 leucin and tyrosin, a small amount of fats and soaps, and a com- 

 paratively large quantity of sodium carbonate, to which the alkaline 

 reaction of the juice is due, and which seems to be peculiarly 

 associated with the albumin. 



Since, as we shall presently see, pancreatic juice contains a 

 ferment acting energetically on proteid matters in an alkaline 

 medium, it rapidly digests itself; and, when kept, speedily changes 

 in character. Perfectly fresh juice appears to contain a substance 

 not unlike myosin giving rise to a sort of coagulation, but the 

 coagulum is soon dissolved. Perfectly fresh juice is also said to be 

 almost entirely free from leucin, tyrosin and peptone, which also 

 seem to be the products of self-digestion. 



Action on food-stuffs. On starch, raw or boiled, pancreatic 

 juice acts with great energy, rapidly converting it into sugar 

 (chiefly maltose). All that has been said in this respect con- 

 cerning saliva might be repeated in the case of pancreatic juice, 

 except that the activity of the latter is far greater than that of the 

 former. .Pancreatic juice and the aqueous infusion of the gland 

 are always capable of converting starch into sugar, whether the 

 animal from which they were taken be starving or well fed. 

 From the juice, or, by the glycerine method, from the gland itself, 

 .an amylolytic ferment may be approximately isolated. 



On proteids pancreatic juice also exercises a solvent action, so 

 far similar to that of gastric juice that by it proteids are converted 

 into peptone. If a few shreds of fibrin are thrown into a small 

 quantity of pancreatic juice, they speedily disappear, especially at 

 a temperature of 35 C., and the mixture is found to contain 

 peptone. The activity of the juice in thus converting proteids 

 into peptone, is favoured by increase of temperature up to 40 or 

 thereabouts, and hindered by low temperatures ; it is permanently 

 destroyed by boiling. The digestive powers of the juice in fact 

 depend, like those of gastric juice, on the presence of a ferment ; to 

 this ferment the name trypsin has been given. A glycerine extract 



