482 J. M. HA MILL. 



of a tryptic digestion mixture which has reached a standstill will enable 

 further proteolysis to occur ; any increase of proteolytic activity 

 observed by Dastre and Stassano was probably due to mere dilution 

 of the mixture by enterokinase or pancreatic juice. Furthermore, 

 Bayliss and Starling' 6 * have brought forward a mass of evidence in 

 support of the view that trypsin is not equivalent to a combination of 

 enterokinase and trypsinogen, as Dastre and Stassano believe, but is 

 an entirely new substance differing in every way from both enterokinase 

 and trypsinogen. They have shown also that enterokinase plays no 

 part in the proteolytic fictivities of trypsin. 



It is obvious, therefore, that the inhibiting effect of worm extract on 

 digestion in an experiment such as that described on page 481 where no 

 enterokinase in any form whatever is present, can be due only to a 

 substance depressing the proteolytic activities of trypsin ; that is to say, 

 the inhibitory effect of the antibody is antitryptic in nature. 



Is the antibody also antikinasic ? It is possible that the antibody in 

 the worm extract, in addition to its antitryptic power, may also possess 

 the power of inhibiting the activities of enterokinase ; that is to say, 

 may be antikinasic. Thus, when enterokinase, pancreatic juice, and 

 worm extract are mixed together, the prevention of the development of 

 proteolytic power in the solution might conceivably be due to the non- 

 conversion of trypsinogen into trypsin owing to the inhibitory effect of 

 the worm extract on the normal activities of the enterokinase. 



In attempting to settle this point we are met at the outset by the 

 difficulty of determining whether the arrest of digestion is due to 

 inhibition of the activity of trypsin already formed, or to the inhibition 

 of the activity of .the enterokinase, thus preventing the transformation of 

 trypsinogen into trypsin. 



In addition to this, the matter is complicated still further by our 

 ignorance of the quantities of the active substances in the solutions with 

 which we are dealing. I have succeeded, however, in devising experi- 

 ments in which these obstacles have been overcome. 



But before describing these, let us examine the evidence which 

 Dastre and Stassano adduce in favour of the antikinasic power of 

 worm extract. These observers' 4 ' mixed worm extract and enterokinase 

 and kept them at 37 C. for 3 to 4 hours. They then added pancreatic 

 juice and a cube of albumin ; the cube did not undergo digestion. This 

 was their crucial experiment, and from it they concluded that the worm 

 extract had destroyed the euterokinase and had thus prevented the 



