The President's Address. By L. S. Beale, F.B.S. 183 



of the ultimate nerve -fibres in various tissues and organs. 

 Indeed, I feel quite sure that at and before that time advance was 

 actually retarded by the discouragement offered in some quarters, 

 and the hypothetical objections raised to the use of very high 

 powers, and more especially to the methods of preparation of the 

 tissues that were necessary before they could with any advantage 

 be submitted to examination. 



Although at this time we can work easily with a twelfth and a 

 twenty-fifth, the results of observation conducted with the aid of 

 such powers are still regarded by some with doubt and incredu- 

 lity ; and if we draw attention to actual structure and arrangement 

 discovered by the higher powers, which could not possibly be 

 demonstrated with the aid of a more moderate lens, our statements 

 may possibly be met with insinuations that what was advanced as 

 the result of observation was, after all, discovered by the imagination 

 only. 



Our present limit of observation in investigations on the struc- 

 ture and action of the tissues of man and the higher animals, in 

 my opinion, includes the use of magnifying powers of upwards of 

 2U00 diameters. Objects considerably less than the hundred- 

 thousandth of an inch in diameter can be studied with success, but 

 how much less than these dimensions cannot, I think, be determined 

 with accuracy at this time ; for so much depends upon the character 

 of the object, and a number of small points of detail as regards the 

 mode of examination. All who are accustomed to work with high 

 magnifying powers are well aware of the great advantages gained 

 by some very slight change in the degree of illuminating power, 

 the direction and concentration of the rays of light, and very slight 

 and happy alterations in the focus, which may momentarily reveal 

 to the mind new facts of the greatest importance after, perhaps, 

 many hours of careful but almost profitless study. 



But in other departments of microscopical research, our present 

 means of investigation enable those familiar with the requisite 

 methods of inquiry to demonstrate characteristics of structure far 

 more intricate and minute than the remarks just made would lead 

 you to infer. Various modifications in immersion lenses and in 

 immersion media have greatly contributed to advance our know- 

 ledge of structure and action in the lower forms of life ; and there 

 is every reason to think that, as time goes on, methods of observa- 

 tion will be still improved and new methods discovered, and that in 

 consequence conclusions already arrived at will have to be greatly 

 modified or entirely changed. Not only so, but by the aid of 

 photography things dimly seen by the eye may be very distinctly 

 and correctly delineated, and with a perfection of accurate detail 

 which a few years ago we should not have supposed to be possible. 

 In all probability, the application of photography to investigations 



