DIGESTION. 103 



the quantity is greatest the quality is poorest, and vice versa. Thus 

 the function of the pancreas in man is intermittent. During secre- 

 tion the gland is very red, and its vessels dilated, and the venous blood 

 red. During repose the gland is flat and of a pale-yellow color, while 

 its blood-vessels are contracted. The secretion is probably caused by 

 secretin and the reflex action due to the contact of the foods. The 

 pancreatic secretion can be moderated or suppressed equally by reflex 

 action, notably in vomiting. 



Of the 3.4 parts of an inorganic nature, the most abundant is 

 sodium chloride, with alkaline and earthy phosphates and alkaline 

 carbonates. The alkalinity of the juice is due principally to the 

 phosphates of sodium. Pilocarpine increases the secretion, while 

 atropine diminishes it. 



The organic matters of the pancreatic juice comprise four prin- 

 cipal enzymes or ferments. They are: (I) trypsin, (2) amylopsin, 

 (3) steapsin, and (4) a milk -curdling ferment. 



Trypsin, a very important constituent of the pancreatic secretion, 

 is much like pepsin of the gastric juice, in that it is a proteolytic 

 enzyme acting on the proteids and transforming them into peptones 

 through intermediate stages. However, its fermentative powers are 

 much stronger and its range of activity extends over more space than 

 do those of pepsin. Atlhough pepsin and trypsin possess many prop- 

 erties in common, yet they are distinctly different and separate bodies. 

 The main, characteristic difference is that pepsin requires an acid 

 medium for its activity, while trypsin acts and performs its functions 

 best in an alkaline solution whose strength ranges from 0.5 to 1 

 per cent. Experiment has proved that trypsin can act in a neutral 

 or very slightly acid medium. 



A remarkable feature of trypsin is the large and rapid transfor- 

 mation of proteid matter of any kind into peptone. This it produces 

 when in only a moderately strong solution. Thus, it is a very capable 

 body to take up the work of proteolysis where the pepsin of the 

 gastric juice left it. since it is particularly a peptone-forming ferment. 

 As the final products of proteolysis, there result peptones. When 

 these come into contact with the pancreatic juice, they are quickly 

 broken down into simple, crystalline bodies, as leucin, tyrosin, aspartic 

 acid, arginin, and a polypeptid. 



Like pepsin, the proteolytic action of trypsin is one of contact 

 also, only it displays its powers more remarkably and energetically, 

 in that it needs no environing bodies to set it in action other than 

 water, the proteid matters, and temperature equal to that of the 



