OCTOBEE 3, 1919] 



SCIENCE 



315 



probable as to amount to practical certainty 

 that the excessively virulent Streptococcus 

 hemolyticus was developed by a process of 

 selection, through successive transfer from 

 person to i)erson, and by gradual enhancement 

 of its invasive properties. 



We are in this case on safe grounds when 

 we assert that the inciting streptococcus is 

 always personally borne : that is, that it leaves 

 the respiratory organs of one person to be 

 introduced upon the corresponding organs of 

 other persons, and in no other manner. In 

 other words, the mechanism or mode of in- 

 fection in epidemic streptococcus pneumonia, 

 as in poliomyelitis, may be said to be clearly 

 apprehended. 



The case of influenza, the third and per- 

 haps the most important example cited, is 

 quite different, since wide divergences of be- 

 lief and opinion regarding the nature of the 

 inciting microorganism and the manner of in- 

 fection still prevail. The reasons for these 

 difi^erences are several, but the most important 

 perhaps relate to the common observation of 

 the manner of spread or attack of the disease. 

 To the casual observer there is something 

 uncanny in the way influenza strikes down its 

 victims. While other epidemics proceed from 

 bad to worse, with at least progressive in- 

 creases in intensity, influenza seems to over- 

 whelm communities over even wide stretches 

 of territory as by a single stupendous blow. 

 While in the one case the gradually acceler- 

 ating rate of speed of extension may be taken 

 to indicate personal conveyance of the pro- 

 voking microorganism, in the other case the 

 sudden wide onset appears to be the very 

 negation of personal communication. 



Hence the invoking of mysterious in- 

 fluences, the revival of the notion of miasm 

 and similar agencies, to account for this phe- 

 nomenon. Indeed, the public mind in general 

 lends itself readily to such formless concepts, 

 for the reason that there still resides in the 

 mass of the people, even in the more enlight- 

 ened countries, a large uneradicated residue 

 of sui)erstition regarding disease. One does 

 not need to look far or dig deep in order to 

 uncover the source of this superstition. We 

 have only recently emerged from a past in 



which knowledge of the origin of disease was 

 scant, and such views as were commonly held 

 and exploited were mostly fallacious. It is 

 indeed very recently, if the transformation 

 can be said to be perfect even now, that the 

 medical profession as a whole has been com- 

 pletely emancipated. All this is very far from 

 being a matter of remote importance only, 

 since in the end the successful imposition of 

 sanitary regulations involves wide coopera- 

 tion, and \mX\\ the majority of individuals 

 composing a community is brought to a fair 

 level of understanding of and belief in the 

 measures proposed serious and sustained en- 

 deavor to enforce them is scarcely to be 

 expected. 



And yet no better instance of a com- 

 mimicable disease could perhaps be invoked 

 than influenza to exorcise the false idea of 

 the mysterious origin of epidemics. To dwell 

 solely on the sudden and overwhelming stroke 

 of the disease is wholly to overlook the sig- 

 niflcant incidents that precede the mass in- 

 fection, because they are of such ordinary 

 nature and lack all dramatic quality. Ac- 

 curate observers noted long ago that influenza 

 in its epidemic form did not constitute an 

 exception to the common rule governing epi- 

 demic diseases which were obviously asso- 

 ciated with persons and their migrations. 

 What the early students made out by tracing 

 the epidemic backward to its point of de- 

 partvire more modem obsei'vers have confirmed 

 by carefully kept records, often graphically 

 compiled, as in the excellent instance of the 

 Munich records covering the epidemic of 

 1889-92, which can now be supplemented by a 

 number of similarly constructed records of 

 the epidemic just passed. These detailed 

 records show convincingly a period of invasion 

 during which there is a gradual rise in the 

 number of cases, to culminate, within a period 

 variously estimated at from one to three 

 weeks, in a widespread so called "explosive" 

 outbreak of the disease. 



It happens that the early cases of epidemic 

 influenza tend not to be severe, chiefly because 

 they rarely are attended by pneumonia and 

 hence are frequently mistaken; and the con- 

 fusion in diagnosis is resolved only when the . 



