22 THE BIOLOGICAL PROBLEM 



distinguished by this instrument. It can easily be under- 

 stood that it is useless to increase the magnification above a 

 certain point if one loses in sharpness what is gained in 

 dimensions. It is a fact of current observation for amateurs 

 of photography, that there is nothing to be gained by enlarging 

 the proofs beyond a certain size, which depends on the 

 quality of the initial negative. 



The preceding pages show that bacteriology is a science 

 which belongs equally to both of the classes which we have 

 examined, since microbes are at the same time individuals 

 and isolated cells. But in fact, bacteriology studies cultures 

 rather than microbes, and it is the entire culture which 

 represents the individual rather than the microbes themselves. 



