48 THE BIOLOGICAL PROBLEM 



protects mice against an infection engendered by the virulent 

 microbes of this type. 



There are few comments to add. As a result of this splendid 

 work we begin to see the dawn of a new bacteriology and 

 immunology, no longer founded on empiricism but on the 

 scientific knowledge of the mechanism and the chemistry of 

 the phenomena of infection and defence. Progress will be 

 long and tedious, but success is certain, for the path is now 

 traced, and though bristling with difficulties it is the only one 

 open to us. And if we remember the methods and principles 

 of Pasteur, chemist and physicist, we realize that it follows 

 the true Pasteurian tradition. 



We have thus far taken a bird's-eye view of biological 

 problems in general. In studying the methods of investigation 

 we have pointed out a few of the difficulties that are 

 encountered. Some are of a purely material nature, mostly 

 due to technical difficulties of all kinds resulting from the 

 inadequacy of methods created to solve the problems of 

 inorganized matter when applied to living matter. Others 

 are of a deeper nature; concerning either the problem in 

 itself or else the mechanism of our thought and the criterium 

 of our reasoning. Finally, however, we succeeded in con- 

 vincing ourselves that at the base of our normal or pathological 

 physiological reactions, chemical phenomena existed that could 

 be approached by our techniques. They are, if one might 

 say so, the material foundation of life, but not life itself. 



Now that we are in possession of these necessary premisses 

 we can proceed to the study of a biological phenomenon of 

 fundamental importance, as it is one of the manifestations of 

 the tendency to persist which characterizes living beings. It 

 is one of the rare problems which can actually be submitted 

 to measurements and calculations, and which, as we will soon 

 see, allows us to introduce time quantitatively in the shape of 

 a variable depending only on the organism as a whole. 



