238 BACTERIOLOGY 



It will be seen that there are many problems before the bacteriologist, 

 problems which have something akin to those of the student of races, 

 varieties, and species among higher forms of life. These problems 

 must be attacked with the same patience and pertinacity that were 

 exercised by Mendel, Darwin, De Vries, and many others in the effort 

 to trace the rise of new species. 



In dealing with the great problems of pathogenesis and parasitism 

 as applied to the micro-organisms in such a summary and hasty man- 

 ner, and in endeavoring to trace the law of a declining virulence (and 

 hence mortality) and an advancing parasitism, I may have left some 

 doubts in the reader's mind concerning the ultimate value of medi- 

 cine, preventive and curative, in controlling these diseases, since it 

 might be assumed, according to the hypotheses presented, that they 

 would take care of themselves. This impression will, I think, be dis- 

 pelled by a little further development of the ideas presented. 



The social and industrial development of the human race is con- 

 tinually leading to disturbances of equilibrium in nature, one of whose 

 direct or indirect manifestations is augmentation of disease. In order 

 to avoid this calamity, or reduce its force as much as possible, we must 

 make special compensations or sacrifices to restore or maintain the 

 normal balance. The more clearly the kind of compensatory action 

 required is foreseen, the more promptly it is put into effect, the less 

 disease there will be. It is the true function of medical science to dis- 

 cover and put into effect those compensatory movements which will 

 counterbalance the temporary ill effects of what, for want of a more 

 illuminating term, we call human progress. 



It is largely through the phenomenon of parasitism that nature 

 attempts to restore the equilibrium, and in this micro-organisms play 

 the most important part. As soon as the individual falls below a cer- 

 tain level he may become the prey of a microscopic, or even an ultra- 

 microscopic world. Hence the importance of bacteriology in medical 

 science. Much has already been done in determining ways and means 

 for the counterbalancing of the ravages of this microscopic world, but 

 science cannot rise above natural law. It must work through it. 

 The optimism of the world frequently places science above natural 

 law and believes it capable of correcting any and all excesses of in- 

 dividuals and races. We may be certain that it will never be able to 

 eliminate the factor of parasitism. Its most important work will con- 

 tinue to be to analyze this factor into its minutest details and to devise 

 means by which this analysis may be made useful in turning aside or 

 at least in deadening the shock of disease. 



