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action of the juice. At present we only wish to state that when 
the drainage-tube was lying in the intestine for a length of 12 c.M., 
10 c.c. were secreted every 24 hours; but when the tube was pushed 
in further to a length of 22 ¢.M., the quantity rose to 170 c.c.; 
and the next day, when the tube was again pushed in only a small 
distance into the intestine, the quantity sank to 70 c.c. 
There is therefore no doubt that in man also a local excitation 
has a powerful influence on the quantity of the secretion. This is 
what one would expect, and no doubt under physiological eireum- 
stances, the amount secreted is regulated by the necessities of the case. 
Summary. 
The following are the principal results obtained from the researches 
described in the foregoing pages : 
1. The intestinal juice examined by us, does not possess the 
power in itself of digesting white of egg or fat; it is however, in 
a smal] degree, able to hydrolyse starch. 
2. Whereas the intestinal juice exercises an extremely small 
influence on the ordinary constituents of food, #t is of great impor- 
tance when it acts in conjunction with pancreatic juice. 
When a freshly excised pancreas is cut into small pieces, pressed 
out and the expressed juice is brought into contact with coagalated 
white of egg no digestion of that substance occurs; if however the 
pancreatic juice is mixed with intestinal juice, then a considerable 
amount of digestion takes place. 
This is best explained on the hypothesis that the proteolytic 
enzyme, trypsin, is not present as such in the juice, but in the 
form of its precursor (trypsinogen); this zymogen is in itself inactive. 
By means of the intestinal juice trypsin is liberated from its zymogen. 
3. This character is lost when the intestinal juice is boiled and 
also when it is heated for 3 hours to 67°. 
4. Pawtow and his fellow-workers, who first drew attention to 
the co-operative action of the two juices in dogs, regard the active 
substance of the intestinal juice as a ferment and have named it 
enterokinase. We do not agree with this, but are of the opinion 
that it is no ferment, rather a compound, which causes a transfor- 
mation of the zymogen into the enzyme, trypsin, in stoechiometrical 
proportion. 
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