November ii, 1922] 



NA TURE 



627 



litis lethargica in the winter months of December to 

 February inclusive. Poliomyelitis, unlike encephalitis 

 lethargica, attacks chiefly children. Experimentally, 

 the unidentified virus of each disease appears to be a 

 filtrable organism, that of poliomyelitis being readily 

 transmissible to monkeys ; that of encephalitis lethar- 

 gica being transmissible with difficulty and only from 

 acute cases of the disease. 



The detailed pathological and bacteriological evi- 

 dence of the separate identity of these two diseases 

 cannot be given here, but it is set out lucidly in Dr. 

 MacNalty's contribution to the report under review. 



The separate identity of influenza is sufficiently indi- 

 cated by its proverbial infectiousness, whereas multiple 

 cases of either encephalitis lethargica or poliomyelitis 

 are a rarity. Even if it be assumed that the appar- 

 ent partial non-infectiousness of these two diseases is 

 due to the incarceration of the hypothetical influenzal 

 virus in the deep parts of the central nervous system, 

 it would still need explanation that the virus when 

 introduced in these cases did not cause, e.g. in other 

 members of the same family, ordinary attacks of in- 

 fluenza. There is no systematic parallelism in the 

 prevalence of the three diseases ; and as Dr. Parsons 

 remarks, " the epidemic behaviour of influenza and 

 encephalitis lethargica do not seem to represent a 

 mutuality of any constant nature." The rarity of respira- 

 tory complications in cases of encephalitis lethargica is 

 in itself a strong argument against community of origin. 



The present reports by Dr. A. C. Parsons, Dr. A. S. 

 MacNalty, and Dr. J. R. Perdrau, with a prefatory 

 statement by Sir George Newman, bring our knowledge 

 of this disease up-to-date. The value of the report is 

 enhanced by an elaborate bibliography of 1243 items, 

 which will be most useful to students of this obscure 

 subject. The extent of incidence of the disease may 

 be gathered from the statement that in 1919, 541 cases, 

 and in 1920, 890 cases, were recognised and notified, 

 and it is not without significance that cases of polio- 

 myelitis became much fewer in the same period. This 

 may be explained on the supposition that a common 

 virus at different times strikes at different parts of 

 the nervous system ; but the totality of evidence, 

 epidemiological, clinical, and pathological, points in 

 another direction. 



We began this necessarily sketchy review with a 

 statement that the group of diseases mentioned above 

 do not yet come within the range of practical preventive 

 medicine. When the agitation in one of our chief daily 

 journals in favour of the much-needed Ministry of 

 Health was at its height, the failure of the Local 

 Government Board to control the pandemic of in- 

 fluenza was a big item in the indictment against it. 

 This report, like the recent official report on influenza, 

 NO. 2767, VOL. I 10] 



should give pause to those who anticipate that un- 

 controllable diseases will be made controllable by 

 changing the name of a government department. It 

 has to be confessed — and from a scientific point of 

 view it is most important to face the fact — that 

 " respiratory infections " like influenza and (pre- 

 sumably) poliomyelitis and encephalitis lethargica are 

 almost entirely uncontrollable, and will remain so until 

 some new method of securing immunity is discovered, 

 or until a standard of hygienic precautions is reached 

 in respect of coughing, and even of speaking, which is 

 not likely to be attained universally in this century- 

 Even were it attainable, would life then be tolerable ? 



Meanwhile, every channel of investigation needs to 

 be pursued ; and a word of praise may be given in this 

 connexion to the wisdom of making encephalitis 

 lethargica notifiable in 1918 as soon as its separate 

 existence was fairly well established. By this means 

 it has become practicable to investigate each notified 

 case and to demonstrate the general absence of 

 personal infection from recognised cases. By implica- 

 tion we are led to infer that slight unrecognisable cases 

 of the disease exist which cause its spread ; but this 

 fact further emphasises the uncontrollable character 

 of the disease in present circumstances. 



Encephalitis lethargica has been described above as 

 a " new disease." This merely means that it is a newly 

 recognised disease. Crookshank and others have 

 searched older literature and found descriptions which 

 tally with this disease, occurring commonly in associa- 

 tion with epidemics of influenza ; and there can be 

 little doubt that the apparent strict modernity of 

 encephalitis lethargica is indeed apparent and not real. 



The Telescope. 



The Telescope. By Dr. Louis Bell. Pp. ix + 287. 

 (London : McGraw-Hill Publishing Co., Ltd., 1922.) 

 155. net. 



INVENTION is not the prerogative of the learned. 

 The telescope, we are told, was the creation of the 

 two little children of an observant father, a spectacle- 

 maker of Holland. But, however casual the origin, 

 its development was the result of laborious and pro- 

 gressive experiment and study, an excellent account 

 of which is given by Dr. Louis Bell in the introductory 

 chapter of the work before us. 



There are partisans who will dissent from some of 

 the author's historical statements, and many who will 

 object to the presentation of Newton as a " blunderer," 

 a " bungler," and a man who promptly jumped to a 

 conclusion. As a boy, Newton tested the wind by 

 jumping with and against it, and Sir David Brewster 

 remarks : " This mode of jumping to a conclusion, or 

 reaching it per saltum, was not the one which our 



