I30 



NATURE 



[February 2, 1922 



bacillus from secretions of influenzal patients and 

 grown it in separate culture, they have failed in the 

 crucial test of inoculation in animals to reproduce 

 influenza. 



This brings us to our next difficulty. In the 

 absence of a certain bacteriological test, a further 

 obstacle is that there is no characteristic symptom 

 in influenza, like the rash in scarlet fever, or the 

 throat membrane in diphtheria. On the contrary, 

 what is supposed to be influenza assumes several 

 types. At present cases with gastric symptoms are 

 common, with few or no respiratory complications in 

 a proportion of cases. But are we certain that these 

 two types are the same disease? There is much 

 evidence that commonly there is mixed infection ; 

 and in the great epidemic of 1 918-19, which 

 destroyed more of mankind than the great war, 

 much of the mortality was due to secondary (or 

 primary) invasion of haemolytic streptococci. 



On such an apparently simple point as the im- 

 munity conferred by a single attack the evidence 

 is discrepant. Although it did appear that many 

 of those attacked in the summer epidemic of 191 8 

 escaped attack in the terrible epidemic of the follow- 

 ing winter, the evidence is not satisfactory. It 

 appears clear that if immunity is conferred by an 

 attack, the immunity is of short duration; and 

 this brings out the further point that inoculation of 

 a vaccine prepared from the Pfeiffer bacillus and 

 the associated coccal organisms cannot be expected 

 to do much good, except perhaps in diminishing the 

 seriousness of pulmonary complications. 



Nor have we any plausible explanation of the 

 remarkable change in the age incidence of deaths 

 from influenza. In the epidemic of 1889-92 some 

 60 to 70 per cent, of all the recorded deaths from 

 influenza occurred among patients more than 

 55 years old; in the recent epidemic, fatal cases at 

 these ages formed only some 12 per cent, of the 

 total, while about 70 per cent, of the total deaths 

 were of patients less than 35 years old. Does this 

 imply that we have recently been concerned with a 

 different infection, or what is the explanation? 



It is noteworthy that coincidently with epidemic 

 influenza, certain other diseases, like cerebro-spinal 

 meningitis and encephalitis lethargica, have pre- 

 i-ailed to an exceptional extent. This has been 

 e T>lained by Dr. Hamer and others as implying that 

 w*# are, in fact, in the grip of a single infection 

 assuming multiform manifestations. But the asso- 

 ciation was not evident in the 1889-92 epidemic ; 

 and it is equally open to us to assume — and there 

 are good grounds for maintaining — that all these 

 diseases, each specific in character, are favoured by 

 NO. 2727, VOL. 109] 



the same " epidemic constitution " — or what is con- 

 cealed under this designation — and that they are 

 not identical diseases. 



The preceding incomplete review of the chief of 

 the unknown factors in influenza must necessarily be 

 somewhat depressing. It is well, therefore, to look 

 for a moment at other diseases which, like influenza, 

 at irregular intervals and for unknown reasons, 

 assume world-wide movements, invading mankind in 

 many countries. Among these cholera, plague, and 

 smallpox may be specially mentioned. Yet each of 

 these is entirely controllable, and, so far as a large 

 part of the world is concerned, has been controlled. 

 Cholera is now kept within bounds and almost non- 

 existent in every country with elementary sanitation. 

 Plague is controllable to the extent to which infec- 

 tion by rats and their fleas is stopped : a practicable 

 programme. In smallpox there is the important 

 additional protection of vaccination, and against a 

 population protected by this measure waves of small- 

 pox infection break for ever impotently. The last- 

 named illustration is significant from the point of 

 view of influenza. Both infections are usually 

 received by the respiratory tract. Against one 

 vaccination affords protection, against the other 

 results of inoculation have been more than dubious. 

 The world is waiting for further light. How is 

 influenza and how are respiratory infections in 

 general to be prevented? This is the unconquered 

 region of preventive medicine. It will doubtless be 

 occupied eventually, but after how much delay and 

 on what plan it would be rash to hazard a prophecy. 



An Elusive Group of Marine Organisms* 



The Free-living Unarmored Dinof.agellata. By 

 C. A. Kofoid and Olive Swezy. (Memoirs of 

 the University of California, Vol. 5.) Pp. viii-j- 

 562-^12 plates. (Berkeley, California: Uni- 

 versity of California Press, 192 1.) 



THE University of California at Berkeley, 

 Cal., supported no doubt by large revenues 

 from the State, sets a noble example in publishing- 

 valuable contributions to knowledge. In addition 

 to about thirty octavo series in zoology, physi- 

 ology, and other sciences, the University Press 

 issues large quarto Memoirs, of which the fifth 

 volume is Kofoid and Swezy 's '* Dinoflagellata," 

 a very notable work of 570 pages and twelve 

 coloured plates. It is the result of observations 

 made by Prof. Kofoid and his pupils over a series 

 of years from 1901 onwards at the marine labora- 

 tories of the University of California and the more 

 recently established Scripps Institution for Bio- 



