347 



Bennett, the drawings of dust obtained from air filtered 

 through gun-cotton are only magnified 180 diameters.^ They 

 demonstrate at any rate the presence in it of fungus spores, a 

 result easily credible to any one who has watched the myriads 

 of them which may be discharged from a single puff ball, 

 darkening the air for a moment or two and then invisibly 

 dispersed, or to any one who remembers the ubiquity of 

 cryptogamic forms. A fortiori if the spores of the larger fungi 

 are present in atmospheric dust, the germs of minuter and 

 obscurer organisms cannot be concluded to be absent, espe- 

 cially if we remember that Professor Tyndall has shown the 

 particles of atmospheric dust to be almost AvhoUy destructible 

 by heat, although of course a large proportion are lifeless 

 matter. In his other investigations Pasteur employed a 

 magnifying power of 350 diameters; but Dr. Child pointed 

 cut that it is quite possible that living particles might exist 

 in a solution and yet not be detected by ibis, and a certain 

 degree of uncertainty has been supposed to attach to Pasteur's 

 results on that account.- It must, how^ever, be remembered 

 that there is no limit to the extent to which this objection 

 may be urged. Dr. Beale thinks that whatever be the mag- 

 nifying power we employ we should still be able to see parti- 

 cles more and more minute of living matter, and experience, 

 as far as it has hitherto gone, appears to justify him. AVith 

 the -s^i\\ of an inch object-glass, which with the low eye- 

 piece magnifies nearly 3000 diameters, " particles too trans- 

 parent to be seen by -^T^^'i- are distinctly demonstrated."^ It 

 is difficult to see how, this being the case, we can ever state 

 with absolute certainty from microscopic observations alone, 

 that any given liquid does not contain living matter. But, 

 on the other hand, it may be fairly presumed that in Pasteur's 

 experiments, carried over, in some instances, a year and a 

 half, the minute fragments of living matter would have grown 

 during that time into visible dimensions ; so that this objec- 

 tion is not really of so mucli practical importance. At any 

 rate there was never any difficulty in detecting the existence 

 of life in solutions which had been previously inoculated with 

 germ-containing dust. 



Dr. Bastian's results are perhaps the most remarkable of 

 any that have hitherto been published, and they could not 

 fiiil to have attracted the most serious attention, perhaps 

 even more so, on their ovvn merits alone, apart from any 

 a jjriori discussions. In all the experiments liquids were 



^ 'Popular Science Review,' vol. viii, p. 5S. 



" ' Proceedings of the Koyal Society/ vol. xiv, p. ISi. 



' Loc. cit., p. 36, 



