NATURE OF PROTEOLYTIC FERMENTS KX) 



pointed out, reagents acting on the characteristic, 

 typical structure of the components of definite kinds 

 of cells. We may illustrate this idea by an example. 

 A great sensation was caused at one time bv the 



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observation, that there were unicellular organisms 

 which apparently showed signs of intelligence. It 

 could be seen under the microscope how the uni- 

 cellular organism, called Vumpyrella spirogyra*, 

 hurried from one alea thread to another, until it 



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stopped at a particular kind of alga in order to use it 

 as food. However many kinds of alga were offered 

 to it, it would always pick out the same kind. This 

 .phenomenon, which seems so amazing at first sight, 

 may doubtless be explained in the following way : 

 Every living being has ferments at its disposal which, 

 as Emil Fischer pointed out, may be compared with 

 keys, and the substrate, against which they are 

 directed, with locks. Just as a particular key gener- 

 ally unlocks and locks only a particular lock, so can 

 particular ferments only decompose or reconstruct 

 substrates of a particular constitution. 



The Vampyrella spirogyrce, then, hurries from alga 

 to alga, bearing with it ferments, by means of which 

 it intends to convert nutriment into a suitable form. 

 It is always trying to effect an entry by means of its 

 'keys,' and it only succeeds in certain cases, 

 namely, when the key fits the lock, which is to 

 say, when the cell-wall of the particular alga is of 



