CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 359 



with permanent fistulse the secretion is apt to become altered in nature, 

 and to lose many of its characteristic properties. Some, however, have 

 succeeded in obtaining permanent fistulse without any impairment of 

 the secretion. 



Healthy pancreatic juice is a clear, somewhat 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) obtained from a temporary fistula is about 8 to 10 p.c. ; but 

 in even thoroughly active juice obtained from a permanent fistula, 

 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 of quite fresh juice are albumin, a peculiar form of 

 proteid allied to myosin, giving rise to a sort of clotting, a small 

 amount of fats and soaps, and a comparatively large quantity of 

 sodium carbonate, to which the alkaline reaction of the juice is 

 due, and which seems to be peculiarly associated with the proteids. 



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

 ferment acting energetically on proteid matters in an alkaline 

 medium, it rapidly digests its own proteid constituents, and, when 

 kept, speedily changes in character. The myosin-like clot is 

 dissolved, and the juice soon contains a peculiar form of alkali- 

 albumin (precipitable by saturation with magnesium sulphate) as 

 well as small quantities of leucin, tyrosin and peptone, which seem 

 to be the products of self-digestion and are entirely absent from 

 the perfectly fresh juice. 



210. Action on Food-stuffs. On starch, pancreatic juice 

 acts with great energy, rapidly converting it into sugar (chiefly 

 maltose). All that has been said in this respect concerning 

 saliva might be repeated in the^ase of pancreatic juice, except 

 that the activity of the latter IB 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 takeh 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 jui$ 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 

 which, as we have already said, may be isolated much in the 



