364 



SCIENCE. 



[N. S. Vol. XXIII. No. 584. 



water-supply polluted with human excre- 

 ments; and when, in 1890, typhoid fever 

 appeared among the citizens to such an 

 extent as to constitute a terrible epidemic, 

 and to cause careful observation and study 

 of the past as well as the present, it became 

 evident that a most important experiment 

 had been going on ever since 1872— quietly, 

 naturally and unobserved — and an experi- 

 ment not merely dire in its consequences, 

 but rich in its sanitary teachings. 



Careful studies of the various phases of 

 this long-continued and tragically-ending 

 experiment showed that the citizens of 

 Lawrence had submitted themselves to, 

 and participated in, conditions such as no 

 premeditating experimenter in his wildest 

 flights of fancy would have dreamed of 

 proposing; for they had, for twenty years, 

 been drinking the diluted excrements and 

 other wastes of a large and dirty city. 

 Further studies revealed the fact that so 

 long as these excrements were unmixed 

 with those of typhoid fever patients no 

 excess of typhoid fever ordinarily appeared 

 in Lawrence, but that if typhoid fever 

 abounded in LoweU then, after the lapse of 

 a period of time such as would be required 

 for its transmission to the citizens of Law- 

 rence, and for its usual incubation, typhoid 

 fever invariably appeared in the lower city. 

 In the end, this unpremeditated experiment 

 proved to be remarkably instructive, for 

 while Lawrence and Lowell were thus un- 

 consciously experimenting, Haverhill, on 

 the same river a few miles below, and 

 Nashua, a few miles above, experimenting 

 with relatively pvire water supplies, suf- 

 fered no excess of typhoid fever. These 

 facts threw great light upon the cause of 

 a constant excess of typhoid fever long 

 characteristic of Lowell, and calmly ac- 

 cepted by the local physicians and sanitary 

 officials as 'endemic' — whatever that might 

 mean— and regarded by them as unavoid- 

 able. For when the opportunity came to 



test their theory by a premeditated experi- 

 ment, namely, the purification of the water, 

 this 'endemicity' of typhoid fever in Law- 

 rence disappeared. It then became clear 

 that the so-called 'endemic' was really an 

 epidemic condition; an epidemic condition 

 characterized by the constant existence of 

 a moderate number of cases, rather than 

 the occasional existence of a great number, 

 i. e., by constancy, rather than magnitude. 



These simple facts will serve quite as well 

 as any more extended discussion to estab- 

 lish the fact which I desire especially to 

 emphasize in this paper, namely, that the 

 experimental method is not necessarily eon- 

 fined to laboratories, or applicable only to 

 individuals. Some of its best examples, 

 and some of its richest fruits, may be found 

 in sanitation, as well as in physiology or 

 hygiene; in the environment, as well as in 

 the individual.^ 



The practical importance of the recog- 

 nition of these facts is very gi*eat. Com- 

 paratively few physicians or sanitarians 

 are in a position to conduct artificial ex- 

 periments of great importance, whether in- 

 side or outside the laboratory, but almost 

 any wide-awake observer, whether he be 

 physician, physiologist, sanitarian or en- 

 gineer, may, if he wiU, find going on all 

 about him natural experiments, the condi- 

 tions of which may often be learned with 

 great accuracy even after the experiment 



' The author believes that a natural and service- 

 able distinction may be drawn between hygiene 

 and sanitation, the former term being kept for 

 those aspects of general hygiene, or the public 

 health, affecting chiefly individuals or groups of 

 individuals, the latter for those affecting chiefly 

 environments. He has used this distinction with 

 advantage for some two or three years past in his 

 teaching and in his writing, e. g., in the Encyclo- 

 pedia Americana, Vol. XIV., article ' Sanitary 

 Science and Public Health,' New York, 1904, and 

 in a paper, ' The Readjustment of Education and 

 Research in Hygiene and Sanitation,' in the forth- 

 coming volume of Proceedings of the American 

 Public Health Association. 



