666 EVENING DISCOURSE. 



that the bacteriologists call the ' filterable viruses.' These are living bacteria so 

 exceedingly small that not only are they invisible in the finest microscopes, but they 

 pass easUy through the minute pores of a Chamberland porcelain filter. D'Herelle 

 has recently discovered the occurrence in certain bacterial cultures of what he calls 

 the ' bacteriophage.' These seem to be excessively minute organisms which can 

 hydrolyse certain ordinary bacteria. They constitute an extremely fine and filterable 

 ' virus.' Quite recently Bechhold and Villa, in the Institute for Colloid Research at 

 Frankfurt, have devised a new and ingenious method whereby these minute organisms 

 can be rendered visible and measured. The process consists in depositing gold on 

 them, strengthening up these gilded individuals as one enlarges the silver particles 

 in an insufficiently exposed negative, and obtaining as end result a sort of metallic 

 skeleton of the original organism. It appears that the individuals of D'Herelle's 

 bacteriophage are small discs whose diameter lies between 35 y.y.. and 100 y.\j.. 

 Now the diameter of an ordinary chemical molecular is of the order of 1 [X[x., i.e. 

 one-milhonth of a millimetre. Colloid particles are much bigger than that. If it 

 be proved beyond all doubt that they are really living organisms, then the individuals 

 of D'Herelle's bacteriophage are comparable in size with kno'vvn colloid aggregates 

 of non-living matter. This result gives rise to strange hopes. If wo can find a 

 complete continuity of dimensions between the living and the non-living, is there 

 really any point where we can say that here is life and there is no life ? That would 

 bo a daring and perhaps a dangerous theme to dwell on at the present time. But 

 where there is hope there is a possibility of research. And who will set a limit to the 

 discoveries that are possible to science in the future ? 



I hope no reader of tliis meagre sketch of mine will call me a materialist or a 

 mecanist. All I have endeavoured to show, however briefly and inadequately, is 

 that the sincere and honest men who are advancing science, whether in the region of 

 life or death, are those who measure accurately, reason logically, and express the 

 results of their measurements in precise mathematical form. A hundred or a thousand 

 years from now mathematics may have developed far beyond the extremest point of 

 our present-day concepts. The technique of experimental science at that future date 

 may be something undreamed of at the present time. But the advance will be 

 continuous, conformal, and homologous with the thought and reasoning of to-day. 

 The mystery of life will still remain. The facts and theories of science are more 

 mysterious at the present time than they were in the days of Aristotle. Science, 

 truly understood, is not the death, but the birth, of mystery, awe and reverence. 



