198 



SCIENCE 



[N. S. Vol. XXVIir. No. 711 



is barely beginniug to be appreciated. 

 Sickaess and death mean everj^where hea^s^y 

 financial burdens wpon tlie family and the 

 eommunitj^ and it is now being realized as 

 never before that Emerson's dictum, "the 

 first wealth is health," is strictly true, not 

 onty for the individual but for the social 

 individual or eommunitj\ New light is just 

 now being shed, for example, upon the 

 economic value of one public health meas- 

 ure, viz., a pure water supply, by a vei'ifi- 

 cation which one of my students and I have 

 made of a theorem suggested indepen- 

 dently, as it seems, by Mr. Mills, the dis- 

 tinguished engineer member of the Massa- 

 chusetts State Board of Health, and Dr. 

 Eeincke, the health ofScer of Hamburg, 

 Germany, but first publicly formulated and 

 published by the eminent American sani- 

 tary engineer, Mr. Allen Hazen. Hazen's 

 theorem asserts that for every death from 

 typhoid fever avoided by the purification 

 of a polluted public water supply, two or 

 three deaths are avoided from other causes. 

 Working under my direction, Mr. Scott 

 MacNutt has recently been able to confirm 

 this surprising theorem, and even to estab- 

 lish it as conservative. "We have also gone 

 further than Hazen and discovered what 

 the other causes are from which deaths are 

 thus avoided ; and, although our results are 

 not yet all published I may say that con- 

 spicuous among these "other causes" are 

 pneiunonia, pulmonary tuberci;losis, bron- 

 chitis and infant mortality. Mr. MacNutt 

 and I have also raised the question. To 

 what is this unexpected result duel But 

 this question we have not j'et been able to 

 answer. It may be that the germs of other 

 diseases than tj-phoid fever are more often 

 waterborne than has hitherto been sus- 

 pected, so that purification of a polluted 

 water supply causes a cessation of in- 

 fection; or it may be that polluted water 

 somehow depresses the vital resistance and 

 so permits micro-organisms which might 



otherwise have been successfully resisted, 

 to gain a fatal foothold ; or it may be that 

 both these factoi-s are at work, and that 

 each is partly responsible for the fortunate 

 x-esult. On this problem we are still at 

 work. 



The city of Pittsburg is just installing a 

 great municipal filter plant for the purifi- 

 cation of its principal water supply, at an 

 expense of upwards of $7,000,000. It is 

 reasonable to estimate that in a year or 

 two this should effect a saving of 100 

 deaths a year from typhoid fever; for the 

 number of tj^hoid fever deaths of late 

 years has been 400 or more yearly. Valu- 

 ing these lives at $5,000 each, as is custo- 

 mary, the saving effected by the purifica- 

 tion works should be half a million of 

 dollars worth of human life annually, 

 making the building of the filter a sormd 

 and profitable economic as well as a hu- 

 manitarian measure. But if, as Mr. Mac- 

 Nutt and I have shown, Hazen's theorem 

 is true, then for every 100 deaths saved 

 from typhoid fever, at least 200 will be 

 saved from other causes; which means at 

 least $1,000,000 more saved to the city of 

 Pittsburg anniially, of its present waste of 

 human life. 



The call to leadership in the public 

 health service is a call to the educated 

 everywhere, but especially to educated 

 physicians. And I would, if I could, im- 

 press upon the young men about to claim 

 that title from this ancient tiniversity, that 

 it is their duty as well as their privilege 

 to lead a willing public on to higher 

 achievements of public as well as private 

 health. It has long been the glory of the 

 medical profession that its members were 

 primarily naturalists rather than super- 

 naturalists, as the word "physician" itself 

 testifies, for it means "a naturalist." That 

 other cognomen of the profession, "doc- 

 tor," points the way to another duty, an- 

 other high and noble function, namely, 

 that of the "teacher." Physicians and 



