November 18, 1904.] 



SCIENCE. 



661 



tion 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 advantageously 

 at many points. We are no longer content 

 to let things as we see them remain as they 

 are. On the surface the wider relations of 

 disease have often seemed of little signifi- 

 cance as, before Darwin, the so-called for- 

 tuitous 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 ca- 

 prices of the genius epidemicus, and it has 

 sometimes been thought idle to ascribe re- 

 current waves of infection to anything but 

 'the natural order.' Another phase, en- 

 tered upon later and from which we have 

 not yet entirely emerged, possesses its own 

 peculiar perils. In meditating on the cos- 

 mos the agile mind is always tempted to fill 

 in the gaps of knowledge with closely knit 

 reasonings or fantastic imagery. The imag- 

 inative man of science still frequently finds 

 himself beset with the temptation to erect 

 an unverifiable hypothesis into a dogma 

 and defend it against all comers. It is 

 now fortunately a truism that a more hvim- 

 drum and plodding course has proved of 

 greater efficacy in advancing natural 

 knowledge. Theories that stimulate to re- 

 newed observation and experiment have 

 been of the greatest service, but unveri- 

 fiable speculations have often been a bar- 

 rier to further advancement. Metaphysics 

 tempered with polemic is not science, what- 

 ever be its allurements. 



If the attainment of a rational position 

 in public hygiene, community hygiene or 

 preventive medicine must then be regarded 

 as the main objective point in the campaign 

 against disease, it follows that the part 

 played by bacteriology in this advance will 

 be an important one. The relations of bac- 



teriology to public hygiene are fundamen- 

 tal. The etiology of many of the most 

 widespread and common diseases that 

 afflict mankind is intelligible only through 

 the medium of bacteriological data. The 

 modes of ingress of the invading micro- 

 organisms, the manner of persistence of 

 the microorganism in nature, the original 

 source of the infectious material and all 

 the varied possibilities of transmission and 

 infection can be apprehended only through 

 the prosecution of detailed bacteriological 

 studies. It is only by this means that 

 the weak point in the chain of causation 

 can be detected and the integrity of the 

 vicious circle attacked. Success will inevi- 

 tably depend upon a thorough understand- 

 ing of the circumstances governing and 

 accompanying the initiation and consum- 

 mation of the disease process. Yellow fever 

 can not be suppressed by burning sulphur 

 or by enforcing a shot-gun quarantine, the 

 bubonic plague is not to be combated by 

 denying its existence. 



In the warfare against the infectious 

 diseases a rational public hygiene is ready 

 to avoid the mistake of beating the air. A 

 preliminary survey of the possibilities re- 

 veals several distinct types of disease; 

 those that are practically extinct or far 

 on the road to extinction in civilized com- 

 munities, those that remain stationary, or 

 decline but slightly, and those that show a 

 more or less consistent increase. The econ- 

 omy of energy would suggest that it is not 

 a far-sighted policy for public hygiene to 

 focus its endeavors exclusively upon those 

 diseases that are yielding naturally before 

 the march of civilization. The conditions 

 under which civilized peoples live to-day 

 are in themselves sufficient to render the 

 foothold of many infectious diseases most 

 precarious. What nation now fears that 

 typhus fever will become a national 

 scourge, or who looks to see the citizens of 

 London driven into the fields by the Black 



