May 30, 1919] 



SCIENCE 



503 



mass of statistical data which has accumulated 

 in cities, towns, camps and hospitals must be 

 assorted, tabulated and studied before it will 

 be possible to speak with anything like finality 

 as to the efficacy of the measures of control 

 employed. 



Until this is done, it will be impossible to 

 give the number of persons attacked, their 

 age, sex, condition and race, the complications 

 and sequela; of the disease, much less the 

 relations which these facts bear to the pre- 

 ventive measures. This work is now engaging 

 the attention of many experts. Public health 

 officers, skillful workers in bacteriology and 

 pathology and able clinicians who have had op- 

 portunity to study the disease intensively are 

 making their reports. It will be months and 

 perhaps years before the records of all the 

 scientific study connected with the pandemic 

 are brought to a conclusion. 



A good deal may confidently be expected 

 of the work which has been done from so 

 many angles and in so many places. How 

 far the mysteries which have obscured the 

 true nature of influenza for so many years 

 will be cleared up must be left for time to 

 show. 



No disease is more difficult to study than 

 pandemic influenza. It comes, it spreads, it 

 vanishes with unexampled suddenness. It 

 possesses such terrific energy that little time 

 is afforded during its visitations in which to 

 study it in a careful and painstaking manner. 

 Both its total absence and its great prevalence 

 stand in the way of its study. 



But, it will be asked, is influenza entirely 

 absent in the intervals between epidemics? 

 Opinion is divided on this point. Some hold 

 that pandemic influenza is a separate infec- 

 tion. Others think it is always with us. It 

 does not ordinarily manifest such a fatal 

 aspect as that recently seen, but many of the 

 symptoms of the usual epidemic and the ex- 

 traordinary pandemic influenza are the same. 

 Perhaps the recent pandemic is best explained 

 on the assumption that a particularly virulent 

 type of the common infection was to blame. 



All attempts at excluding influenza from a 

 community seem to have failed. There is 



one and only one way to absolutely prevent 

 it and that is by establishing absolute isola- 

 tion. It is necessary to shut off those who 

 are capable of giving off the virus from those 

 who are capable of being infected, or vice 

 versa. This is a very difficult procedure. 

 First, it is difficult because it is impossible 

 to discover all the virus producers. Second, 

 it is difficult because it is impossible to know 

 who are and who are not immune. Complete 

 isolation is not feasible for entire cities nor 

 for parts of cities, nor for individuals in 

 cities. It is feasible for some small towns 

 and villages, and some have tried it with 

 success. The fact that in many instances the 

 attack has been merely postponed by no means 

 invalidates the principle. 



It is natural to suppose that a phenomenon 

 of such general nature as the influenza pan- 

 demic has had an equally general cause and 

 the only cause which most people can think 

 of as general enough to give rise to a world 

 pandemic is one which possesses an atmos- 

 pheric or terrestrial character. This is a very 

 old conception and one which has survived 

 all others so far as the general public is con- 

 cerned. In one of its forms it is known 83 

 Sydenham's theory of epidemic constitution. 

 In spite of the repeated statement that this 

 theory has been discredited, there are many 

 well-informed persoiis who believe as Syden- 

 ham did that there are general conditions be- 

 yond our knowledge which help to cause dis- 

 ease to assume a different aspect and pre- 

 valence in some years and at some seasons 

 than at others. 



As late as the pandemic of 1889-90 it was 

 thought by many that the cause of the in- 

 fluenza outbreak was in some way connected 

 with world conditions and quite independent 

 of human intercourse. To-day there are some 

 who think that the extraordinarily cold winter 

 of 1917-18 followed by the hot summer was 

 largely responsible for the recent pandemic. 

 Others believe that the great war precipitated 

 the plague. Not a few think that the in- 

 fection was spontaneously developed in many 

 places at about the same time. The argu- 

 ments which have been made in support of 



