July 8, 1922] 



NA TURE 



in which the nervous centres are seriously affected, and 

 in which the varieties of disease included in the Heine- 

 Medin symptom complex occur. 



Dr. Hamer evidently looks to a filter-passing organism 

 as the likely key to the position, and avers that " most 

 of the ' causal organisms ' of bacteriology can be shown 

 to be mere upstart associated organisms or secondary 

 invaders." Using Dr. Crookshank's conception that 

 three fundamental factors are concerned, namely, the 

 disease, the epidemic, and the epidemic constitution, 

 Dr. Hamer advocates the hypothesis that the cause of 

 the disease, of the epidemic, and of the epidemic con- 

 stitution " is the mutating lera causa or primary 

 influence," which may be some ultra-visible organism. 

 Much stress is laid on the epidemics which commonly 

 precede and follow, or are associated with, typical 

 influenza. Dr. Hamer evidently thinks that much 

 of the trench fever in the recent war was influenza. 

 This may be so, in a proportion of the cases in which 

 an error of diagnosis was made ; but this would not 

 apply to the cases of true trench fever, the communi- 

 cability of which by body lice has been demonstrated. 

 A reference to Malta fever is similarly confusing ; for 

 if this is to be regarded as belonging to the large 

 influenzoid group, it is remarkable that it should be 

 entirely preventible by boiling all goat's milk which is 

 consumed by human beings. In Dr. Hamer's words, 

 " in thickly inhabited areas of the globe a kind 

 of law of coincidence or of overlapping of cerebro- 

 spinal fever and poliomyelitis and pandemic influenza " 

 is visible. This relationship it is maintained is " not 

 simply and solely one of concurrence, but of regulated 

 development in definite sequence," and Creighton, our 

 leading historical epidemiologist, is quoted in favour of 

 the contention that we must keep in mind " gradations, 

 modifications, affinities," and be " careless of symmetry, 

 of definitions or clear-cut nosological ideas, or the 

 dividing lines of a classification." 



With this general proposition we are in accord, and 

 we may agree also that fixity of type of epidemic 

 diseases and their causal organisms is not to be assumed; 

 but, taking the three diseases just named, it requires 

 much imagination even to assume that they can all 

 be due to variants of a common infection. Our know- 

 ledge of the infecting agent in poliomyelitis is now 

 considerable ; and although the proof that the meningo- 

 coccus is the cause of cerebro-spinal fever is not abso- 

 lutely complete, the converging evidence of bacteriology 

 and vaccinal treatment is strongly in favour of this con- 

 clusion. Without adequate reason, to assume that the 

 contagia of diseases which are commonly associated are 

 variants of a common contagium is a retrograde scien- 

 tific step ; it appears much more probable that the 

 true explanation of the frequent association or sequence 

 NO. 2749, VOL. I 10] 



of influenza, poliomyelitis, encephalitis lethargica, and 

 cerebro-spinal fever is that the " epidemic constitution ' ' 

 in these years favours the whole group of infections 

 and not merely one of them — influenza. There is 

 close analogy between this view and the view which 

 explains the coincidences and sequences in seasonal 

 and pandemic occurrence of scarlet fever, puerperal 

 fever, rheumatic fever, diphtheria, to which attention 

 has been directed in investigations by Longstaff and 

 Newsholme. It can scarcely be contended that all 

 these diseases are manifestations of a common infecting 

 agency. 



The view just stated appears to be confirmed in the 

 article in the present volume by Dr. Dwight Lewis of 

 Newhaven, U.S.A. Classical influenza, in his view, is 

 caused by the Pfeiffer bacillus, but " the various waves 

 of the so-called pandemic of influenza were caused by 

 consecutive and increasing prevalences of correlated 

 diseases due to the activation of carriers of the organ- 

 isms of these diseases, whether by the influenza bacillus 

 or by the streptococcus." There is no difficulty in 

 believing in what we may call a first-cousinship of 

 diseases, in the influence of one or other of these in 

 increasing the virulence of another, and especially in 

 believing in the death-dealing quality of their com- 

 bined operation, as, for example, that of the organism 

 of influenza and of the Streptococcus hcemolyticus. 



The criticisms in the last chapter of the Government 

 report on influenza are interesting. There is just 

 enough truth in the statement that " what is not 

 recorded, or is not known to be recorded, does not 

 officially happen," to give it tang. 



Dr. Crookshank appears to differ gently from Dr. 

 Hamer in the description of the intercurrent maladies 

 as " phases of influenza," and suggests that these 

 " specialised " epidemics should be described as 

 influenzoid. With considerable imagination, he suggests 

 that the recognition of these would be the first step 

 towards the foretelling of the imminence of pandemic 

 influenza. If this ever become practicable, it will 

 constitute an important advance in our knowledge ; 

 but meanwhile we are all familiar with sporadic cases 

 of these diseases which are not followed by epidemic 

 influenza. 



In short, this contribution to the subject is provoca- 

 tive of thought ; and we hope also that it will lead to 

 more exact epidemiological as well as bacteriological 

 investigation. It presents a better philosophy of 

 epidemicity than is usual ; and Dr. Crookshank's 

 contributions on this aspect of the problem will repay 

 study. We rather think, however, that he is somewhat 

 astray in apparently thinking that the importance of 

 " epidemic constitution " — as a factor in producing 

 pandemicity — is not generally recognised. This is the 



