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of such enzymes by decomposing fibrin. Reflecting on this 

 anomalous behaviour, Vines was led to substitute in his experi- 

 ments proteids more closely allied to those existing in plants, 

 such as the various forms of proteose. Using these he found 

 evidence of proteoclastic action in cases in which the plant had 

 failed to act on fibrin. This result seemed surprising; the 

 action attributed to trypsins, to which these enzymes were held 

 to belong, was clearly divisible into two separate parts, and 

 enzymes were contained in many plants which could only begin 

 in what had been thought to be the middle of the digestion and 

 carry it thence to completion. 



From that time onwards Vines directed his attention to the 

 question whether the so-called trypsin was a single enzyme, 

 working in two separate stages, or whether it was not to be 

 regarded as a mixture of a fibrinoclastic with a peptoclastic 

 enzyme. 



It was at this point in his researches that Vines says he 

 became acquainted with the then recently published researches 

 of Cohnheim, to which attention is called above, which naturally 

 strengthened him in adopting the latter hypothesis of the 

 constitution of the vegetable proteases. His conclusions are 

 thus stated : " It would appear, therefore, that plants form two 

 distinct kinds of proteases, the one a trypsin, the other an 

 erepsin ; and so far as the facts go, they indicate that the former 

 is generally associated with depositories of proteid nutriment, 

 such as seeds, fruits, bulbs, laticiferous tissue, etc. ; the latter 

 with ordinary foliage-leaves, stems and roots. But further 

 research is required in order to definitely establish this dis- 

 tinction." 



In the pursuance of this idea Vines turned his attention to 

 papain as the enzyme which has been, perhaps, more frequently 

 the subject of research than any other. The results that have 

 been obtained with it by different workers have been somewhat 

 conflicting, both as to the conditions of its action and the bodies 

 to which it gives rise. This may be due to the fact that so far 

 the experiments with it have been made with commercial 

 preparations and not with fresh extracts of the actual fruit. 

 The results can scarcely be concordant where there is no 

 uniformity of material. On looking over the earlier work of 

 Martin, Sharp, Halliburton, and others, the chief differences of 

 opinion are found to relate to the question of the appearance of 



