146 



NA TURE 



{Dec. 19. 1889 



as of the intermittent appearances of influenza, probably 

 is that this is in Europe not an indigenous disease, but 

 one imported from Asia. Possibly we may some day 

 track it to its original home in the East, as the old plague 

 and the modern cholera have been traced. 



As regards, however, the European distribution of influ- 

 enza, it has often been thought to depend upon the pre- 

 valence of easterly and north-easterly winds. There are 

 many reasons for thinking that the contagium of this 

 disease is borne through the air by winds rather than by 

 human intercourse. One reason for thinking so is that 

 it does not appear to travel along the lines of human com- 

 munications, and, as is seen in the infection of ships at 

 sea, is capable of making considerable leaps. The 

 mode of transmission, too, would explain the remarkable 

 facts noticed above of the sudden outbreak of the disease 

 in certain places, and its attacking so many people simul- 

 taneously, which could hardly be the case if the infection 

 had to be transmitted from one person to another. 



Another important question, and one certain to be often 

 asked, is suggested by the last — namely, whether influenza, 

 is conta gious. During former epidemics great care was 

 taken to collect the experience of the profession on this 

 point, and its difficulty is shown by the fact that opinions 

 were much divided. Some thought the disease could be 

 transmitted by direct contagion, while others doubted it. 

 But there was and is a general agreement that this is not 

 the chief way in which the disease spreads, either in a 

 single town, or from place to place. 



We must avoid the fascinating topic of the cause of 

 influenza, or our limits would be speedily outrun. But 

 one simple lesson may be drawn from the facts already 

 mentioned — namely, that the disease is not produced by 

 any kind of weather, though that, of all possible causes of 

 disease, is the one most often incriminated in this coun- 

 try. It is true that some of our worst epidemics have 

 occurred in winter, but several have happened in summer ; 

 and the disease has been known in all parts of the world, 

 in every variety of climate and atmospheric condition ; 

 so that it is certainly not due to a little more or less of 

 heat or cold, moisture or dryness. Its constancy of type, 

 the mode of its transmission, its independence of climatic 

 and seasonal conditions, all suggest that its cause is 

 " specific," — that is, having the properties of growth and 

 multiplicatiorf which belong to a living thing. 



Whether the disease affects the lower animals is not 

 absolutely certain, but the human epidemic has often 

 been preceded or accompanied by an epidemic among 

 horses of a very similar disease. It is pretty well known 

 that such a disease is now very prevalent among horses 

 in London. Nearly three weeks ago, one of the railway 

 companies in London had 120 horses on the sick list, 

 and the epidemic is still by no means extinguished. To 

 a certain extent this must be taken as prognostic of human 

 influenza. 



It may be asked, if the influenza is really to come, can 

 we form any notion how soon it is likely to appear ? On 

 such a point little beyond speculation is possible, for the 

 rate at which the disease travels is extremely variable. 

 Generally, it has taken some weeks, or even months, 

 to traverse Europe, but occasionally much less, as, for 

 instance, in 1833, when it appeared to travel from Berhn 

 to Paris in two days. It is now barely a month since 



the epidemic became noticeable in Petersburg, where, 

 according to a correspondent of the British Medical 

 Journal, it began on November 15 or 17, though 

 sporadic cases had undoubtedly occurred earlier. In the 

 beginning of December it was already widely spread 

 throughout Russsia, and, as it would seem from the pub- 

 lished accounts, must have been in Berlin about the 

 same time. In Paris the first admitted and recorded 

 cases occurred about December 10, though doubtless 

 there were cases before that date. Both public and 

 private accounts report it exceedingly prevalent there 

 now. In London, notwithstanding the abundance of 

 colds and coughs, and the mysterious rumours which 

 have been afloat, it appears to the present writer doubt- 

 ful whether any cases of true influenza have yet occurred. 

 But according to its apparent rate of progress, it might, 

 if coming from Paris, have already arrived here ; and it may 

 be breaking out even while these lines are going through the 

 press. But, on the whole, one would be disposed to give 

 the epidemic another week or two. If its distribution 

 depends, as it seems to do, on the winds, it is impos- 

 sible to prophesy with much plausibility. A steady breeze 

 setting in from one of the affected places might bring us 

 an invasion in a very short time ; but the current of air 

 would have to be continuous over the whole district. 

 Light local winds, whatever their direction, would, if the 

 hypothesis be correct, have little effect. On the other 

 hand, a steady frost, with an " anticyclone " period, might 

 effectually keep off the disease. If, then, there is any- 

 thing in the views above stated, prophecy belongs rather 

 to the province of the weather-doctors than of the medical 

 doctors. 



Should the prospect seem a grave one, it may be some 

 consolation to remember that an epidemic of influenza 

 rarely lasts more than a few weeks — three to six — in one 

 place ; that it is rarely a fatal disease, though affecting 

 large numbers of people ; and that the present epidemic 

 seems to have displayed on the Continent a decidedly 

 mild type, which, according to the general rule, it is 

 likely to retain. J- F. P. 



THE HORNY SPONGES. . 



A Monograph of the Horny Sponges. By Robert von \ 

 Lendenfeld. (London : Published for the Royal Society 

 by Trubner and Co., Ludgate Hill, 1889.) 



WITHIN the last few years, and as a direct result of 

 the famous Expedition of the Challenger, three 

 most important monographs of the sponges belonging to 

 the groups of the Hexactinellida, Monaxonida, and the 

 Tetractinellida have been published, nor must the valuable 

 contributions by Polejaeff to the history of the remaining 

 groups, Calcarea and Keratosa, be overlooked. The 

 Calcarea had the advantage of having been already 

 monographed by Haeckel, and so there only remained 

 the Horny Sponges to be fully described, in order that 

 the natural history of the sponges should be up to date. 



Such a work has now been accomplished — thanks to 

 the liberality of the Royal Society— by the labour and 

 scientific skill of Dr. Robert von Lendenfeld. This mono- 

 graph forms a fine quarto volume of over 900 pages, with 

 an atlas of fifty lithographed plates. 



While a student at the University of Graz, Lendenfeld 



