706 PHYSIOLOGY 



their action the co-operation of two bodies, the amboceptor and the complement. 

 If this were correct there should always be a proportionality between the quantities 

 of trypsinogen and enterokinase respectively which are necessary to form trypsin. 

 It has been shown by Bayliss and Starling that this proportionality is not present. The 

 smallest quantity of enterokinase is sufficient to activate any amount of trypsinogen 

 if sufficient time be allowed. The effect of increasing or diminishing the amount of 

 enterokinase is not to alter the total amount of trypsin finally produced, but merely 

 the time taken for its production. This behaviour characterises a ferment, and we may 

 therefore conclude that the view originally put forward by Pawlow is correct, namely, 

 that trypsin is produced from trypsinogen under the action of a ferment enterokinase. 

 If pancreatic juice be allowed to stand, even with the addition of toluol to prevent 

 bacterial infection, it gradually acquires a certain degree of activity. If, however, 

 sodium fluoride be used as an antiseptic the juice remains permanently inactive. 

 The spontaneous activation of the juice may be hastened by neutralisation. The most 

 potent means next to enterokinase is the addition of lime salts. If a few drops of 

 10 per cent, calcium chloride solution be added to fresh pancreatic juice, the calcium 

 being in such a quantity as to suffice to combine with all the carbonate present in the 

 juice, complete activation of the juice occurs within a couple of days, no further 

 increase in its digestive powers being obtained on subsequent addition of enterokinase. 

 It has been suggested that the action of calcium is in some way to assist in the pro- 

 duction of an enterokinase from some precursor of this body already present in the 

 juice. According to Mellanby, the calcium acts simply by neutralising the juice and 

 thus allowing minute traces of enterokinase already present in the juice to exert their 

 effect. It is not likely that this calcium activation plays any part in the normal pro- 

 cesses of digestion, since for its completion it needs twelve to sixteen hours, whereas 

 the enterokinase present in the succus entericus will effect the activation of the juice 

 within a few minutes. 



THE ACTION OF PANCREATIC JUICE ON MILK 

 On the addition of pancreatic juice to milk a clot is produced which 

 speedily redissolves. If re-solution takes place too rapidly the production 

 of a formed clot may be missed. In every case, however, on heating the milk 

 a few minutes after the addition of the trypsin a clot is obtained. How far 

 this action is to be ascribed to the proteolytic ferment trypsin, or how far 

 it is due to the presence of a free rennet-like ferment in the juice, is not yet 

 definitely settled. Since the rennet action is parallel to the proteolytic 

 activity of the juice, it is probable that we must regard the clotting of milk 

 as the first stage in its proteolysis. 



THE ACTION OF PANCREATIC JUICE ON CARBOHYDRATES 

 The pancreatic juice, as well as fresh extracts of the pancreas itself, 

 contains a strong amylolytic ferment, diastase, amylase, or amylopsin. 

 If a few drops of pancreatic juice be added to a 1 per cent, solution of boiled 

 starch, within a few seconds the solution clears, and in half a minute, on the 

 addition of iodine, a red colour is obtained, showing the presence of erythro- 

 dextrin. At the end of a few minutes no colour is obtained with iodine, and 

 the solution contains maltose. The stages in the hydrolysis of starch 

 brought about with pancreatic juice are exactly similar to those effected 

 by ptyalin. If the juice be neutralised, the process of hydrolysis goes on 

 to the formation of dextrose or glucose. This further conversion is due to 



