WITH THE MICROSCOPE. 283 



living organisms discoverable by a power of 10,000 linear, has been 

 living and growing for some time before it attained sufficient dimen- 

 sions and density to be visible to us. I believe if magnifying power 

 could be efficiently increased to ten times ten thousand diameters, 

 we should only be able to see particles of living matter increasing 

 in size, and giving rise to new particles, which in their turn become 

 detached and so on. We should see nothing like the aggregation 

 of particles, or the coalescence of already existing particles, of inani- 

 mate matter to form a mass of living matter. We should see, I 

 believe, nothing but the increase in size and division of living parti- 

 cles already in existence. We might, however, be able to demon- 

 strate germs of a degree of minuteness not yet thought of. But there 

 is another matter of the greatest importance in the consideration of 

 this subject, which has almost entirely escaped notice. Besides extreme 

 minuteness in size, extreme tenuity or transparency may interfere 

 with the detection of an object. Now, the greatest difference is 

 observed in object-glasses in this particular. The best object-glasses 

 will define clearly and accurately, bodies, which, from their trans- 

 parency, are quite invisible under objectives only slightly inferior to 

 the first. I feel quite sure that many statements recently made with 

 reference to the mode of formation of the lowest forms of life, by 

 the process of aggregation of particles, arise from imperfect means 

 of observation, and that the real germs existed for a long time 

 before they possessed sufficient density to be recognised by the 

 object-glasses employed. 



Objects which would be passed over by the observer and remain 

 quite unnoticed when examined by ordinary powers at once attract 

 attention if very highly magnified. If, therefore, high powers were 

 of service only in bringing important but most delicate peculiarities 

 of objects under observation if by their use the attention were 

 merely directed to minute points which would otherwise pass unob- 



How entirely inadequate is such a power for the purpose of demonstrating the 

 absence of these minute organisms from a sample of fluid, is shown by the fact that 

 some of the bacterians figured in my paper in the Proceedings of the Royal Society, 

 vol. XIV, p. 171, measure only about the 3-3-5-0 o' f an mcn - ^ n object of this 

 size when examined with a power of 350 would appear to the eye little more than 

 Ti-i-o of an inch in diameter, and it is evident that any number of such objects might 

 be easily overlooked. In confirmation of this view I may cite the experience of 

 Prof. Rallies of Jena, who, though he confirms in the main the results arrived at 

 by M. Pasteur, yet in his recent work Gahrungs-Erscheinungen (p. 50-51) insists 

 strongly upon the necessity of using high powers in investigations of this nature. 

 He has been in the habit of using .powers of 1,000 and 1,500 diameters, and 

 speaks of having met with organised bodies so minute as to appear as mere points 

 even when so examined (p. 70)." This it will be observed is quite confirmatory 

 of my own observations as stated in the text. L. S.B. 



