PANCREATIC DIGESTION. 341 



tury canal; ptyalin from the saliva; pepsin from the sto- 

 mach; water, partly swallowed and partly derived from the 

 salivary and other secretions;, the peculiar constituents of 

 the bile and pancreatic juice and of the intestinal secretions; 

 some undigested proteids; unchanged starch; oils from the 

 fats eaten; peptones formed in the stomach but not vet 

 absorbed; possibly salines and sugar which have also escaped 

 absorption in the stomach; and indigestible substances 

 taken with the food. 



The Pancreatic Secretion is clear, watery, alkaline, and 

 much like saliva in appearance. The Germans call the 

 pancreas the " abdominal salivary gland." In digestive 

 properties, however, the pancreatic secretion is far more 

 important than the saliva, acting not only on starch but, 

 also, on proteids and fats. On starch it acts like the saliva, 

 but more energetically. It produces changes in proteids 

 similar to those effected in the stomach,, but by the agency 

 of a different ferment, trypsin; which differs from pepsin in 

 acting only in an alkaline instead of an acid medium. On 

 fats it has a double action. To a certain extent it breaks 

 them up, with hydration, into free fatty acids and glycerine; 

 for example 



Calls 

 CaH 



1 Stearin + 3 Water = 3 Stearic acid + 1 Glycerine. 



The fatty acid then combines with some of the alkali pres- 

 ent to make a soap, which being soluble in water is capable 

 of absorption. Glycerine, also, is soluble in water and dialy- 

 zable. The greater part of the fats are not, however, so 

 broken up, but are simply mechanically separated into little 

 droplets, which remain suspended in the chyle and give it a 

 whitish color, just as the cream-drops are suspended in 

 milk, or the olive-oil in mayonnaise sauce. This is effected 

 by the help of a quantity of albumin which exists dissolved 

 in the pancreatic secretion. In the stomach, the animal 

 fats eaten have lost their cell-walls, and have become melted 

 by the temperature to which they are exposed. Hence 

 their oily part float free in the chyme when it enters the 



