THE RELATIONS OF BACTERIOLOGY 211 



teriologic method into the field of protozoon pathology has been 

 already referred to, and constitutes one of the latest and most hopeful 

 developments in the study of the infectious diseases. Medicine, 

 perhaps more than any other department of human knowledge, is 

 most indebted to and maintains the most intimate relations with 

 the science of bacteriology. 



At the present time the relations of bacteriology to public hygiene 

 and preventive medicine seem to me of particular importance, and 

 it is upon this theme that I wish chiefly to dwell. Personal hygiene 

 is not necessarily pertinent to this topic, but falls rather into the 

 same province with the healing art. Matters of diet, of clothing, of 

 exercise, of mental attitude, affect the individual, and contribute 

 more or less Largely to his welfare. But except in so far as the indi- 

 vidual is always of moment to the community, they do not affect 

 the larger problems of public hygiene. The pathologic changes that 

 take place in the tissues of the diseased organism and the methods 

 that must be employed to combat the inroads of disease in the 

 body of the individual patient must for a long time to come remain 

 questions of supreme importance to the human race. But over and 

 above the treatment and cure of the diseased individual, and the 

 investigation of the processes that interfere with the proper physi- 

 ologic activities of the individual organism, rises the larger and 

 more far-reaching question of the prevention of disease. 



Racial and community hygiene are but just beginning to be 

 recognized as fields for definite endeavor. The project may seem 

 vast, but the end in view is undoubtedly the promised land. More 

 and more will the problems of curing an individual patient of a spe- 

 cific malady become subordinated to the problem of protection. 

 More and more will scientific medicine occupy itself with measures 

 directed to the avoidance of disease rather than to its eradication. 



Whatever else may be said of it, this is certainly the age of delib- 

 erate scrutiny of origins and destiny. Man no longer closes his 

 eyes to the possibilities of future evolution or to those of racial 

 amelioration. If we are to remain to a large extent under the sway 

 of our environment, we can at least alter that environment advan- 

 tageously at many points. We are no longer content to let things 

 as we see them remain as they are. On the surface the wider rela- 

 tions of disease have often seemed of little significance, as, before 

 Darwin, the so-called fortuitous variations in plants and animals 

 were considered as simple annoyances to the classifier; the causes 

 of this variation were deemed hardly worth investigation. The rise 

 and fall of plagues and pestilences have been readily attributed to 

 the caprices of the genius epidemicus, and it has sometimes been 

 thought idle to ascribe recurrent waves of infection to anything 

 but "the natural order." Another phase, entered upon later, and 



