662 



SCIENCE. 



[N. S. Vol. XX. No. 516. 



Death? It is of course true that the con- 

 tinuance of this immunity can be secured 

 only by unremitting watchfulness, although 

 so long as existing conditions of civilized 

 life are maintained the recurrence of great 

 epidemics will be relatively remote. The 

 pestilences that once stalked boldly through 

 the land slaying their ten thousands are 

 now become as midnight prowlers seeking 

 to slip in at some unguarded door within 

 which lie the young and the ignorant. 

 Already some once dreaded maladies have 

 become so rare as to rank as medical curi- 

 osities, and their ultimate annihilation 

 seems assured. 



There are other diseases, however, that 

 civilized life, or, at least, modern life, ap- 

 pears to leave substantially unchecked, and 

 some that it even fosters. These may be 

 considered as shining marks for the mod- 

 ern hygienist. The scale between hygienic 

 gain and loss is always in unstable equi- 

 librium. There is no such thing as con- 

 sistent improvement all along the line. 

 As Amiel wrote in his journal, ' in 1,000 

 things we advance, in 999 we fall behind; 

 this is progress.' It is almost a biological 

 axiom that progress in one particular en- 

 tails loss in others. To maintain the effi- 

 ciency of all parts of the complex of civi- 

 lization calls for eternal vigilance. It may 

 be that while we are waxing complacent 

 over the fact that the opportunities for 

 infection with certain parasites are dimin- 

 ishing and that other parasites are grad- 

 ually losing what we vaguely denominate 

 as their virulence, unforeseen and greater 

 evils are raising their heads. The increas- 

 ing exemption from certain diseases will 

 itself lead to an increased prevalence of 

 others as diversely vulnerable age-groups 

 are formed. In general it will occur that 

 the diseases peculiar to the advanced age- 

 groups will increase as the diseases of 

 childhood and youth succumb to hygienic 

 measures. A different age-distribution of 



the population will bring in its train new 

 problems of preventive medicine, which 

 must be successfully solved if the issue is to 

 be fairly met. 



There are not lacking instances of a 

 dawning consciousness on the part of man- 

 kind that the proper development of public 

 hygiene involves a far more comprehensive 

 view of its relations than has hitherto been 

 taken. The study of tuberculosis is being 

 approached by methods of unexampled 

 broadness. We are just beginning to rec- 

 ognize the way in which the roots of this 

 destructive malady are well-nigh inextri- 

 cably interwoven with the whole social 

 fabric. Bacteriological, architectural and 

 economical data are all levied upon for 

 contribution to our knowledge of what is 

 universally recognized as one of the most 

 important of all human diseases. Here, 

 as elsewhere, the care and cure of the in- 

 fected individual still looms large, but be- 

 yond and above this is beginning to be 

 placed the prevention of infection, the dry- 

 ing up of the stream at its source. That 

 for this heavy task public hygiene will 

 require the aid of many workers in many 

 different fields is abundantly evident. For 

 all of them, however, bacteriology must 

 furnish the only definite point of view. In 

 the full consideration of the ' exciting 

 causes ' the tubercle bacillus can never be 

 allowed to drop into the background. 

 Given foul air, insufficient food, inhalation 

 of dust, excessive and exhausting labor 

 and the other deplorable accompaniments 

 of modern industrialism, and it still must 

 be constantly kept in mind that without the 

 tubercle bacillus these predisposing causes 

 would never result in a single case of 

 tuberculosis. On the other hand, without 

 these contributing factors, the tubercle 

 bacillus would almost sink to the level of 

 the negligible ' non-pathogenic organism.' 

 Witness the impotence of the bacillus to 

 produce infection or even maintain itself 



