62 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



The inorganic substances in pancreatic juice are — 

 Sodium chloride, which is the most abundant, and smaller quanti- 

 ties of potassium chloride, and phosphates of sodium, calcium, and 

 magnesium. The alkalinity of the juice is due to phosphates and 

 carbonates, especially of sodium. 



ACTION OF PANCREATIC JUICE 



The action of pancreatic juice, which is the most powerful and 

 important of all the digestive juices, may be described under the 

 headings of its four ferments. 



1. Action of Trypsin. — Trypsin acts like pepsin, but with certain 

 differences, which are as follows : — 



(a) It acts in an alkaline, pepsin in an acid medium. 



(b) It acts more rapidly than pepsin ; deutero-proteoses can be 

 detected as intermediate products in the formation of peptone. 

 Primary {i.e. proto- and hetero-) proteoses have not been found ; the 

 action is apparently too rapid to admit of their detection. 



(c) An albuminate of the nature of alkali-albumin is formed in 

 place of the acid-albumin of gastric digestion. 



(d) It acts more powerfully on certain albuminoids (such as elastin) 

 which are difficult of digestion in gastric juice. Collagen, however, 

 is not digested. 



(e) Acting on solid proteids like fibrin, it eats them away from 

 the surface to the interior ; there is no preliminary swelling as in 

 gastric digestion. 



(/) Trypsin acts further than pepsin, on prolonged action partly 

 decomposing the peptone which has left the stomach into simpler 

 products, of which the most important are leucine and tyrosine. 



Besides leucine and tyrosine, smaller quantities of aspartic acid 

 [amido-succinic acid, C2H3(NH2)(COOH)2], glutamic acid [amido- 

 pyrotartaric acid, C;jH5(NH2)(COOH)2], lysine, arginine, ammonia, 

 and a substance of doubtful nature called tryptophan are also formed ; 

 tryptophan gives a reddish -violet colour vnth chlorine or bromine 

 water. 



Kiihne considered that the peptones which leave the stomach may 

 be arranged into two classes : (1) hemipeptone, which is split by the 

 prolonged action of pancreatic juice into the substances (leucine, 

 tyrosine, &c.) just enumerated ; and (2) antipeptone, which resists 

 this further action. 



This theory held the field for many years, but recent researches 

 have shown that it has little or no foundation in fact. 



We know that the action of proteolytic enzymes is by the process 



