184 Transactions of the Society. 



upon minute structural details will be carried far beyond anything 

 yet reached, although it is really wonderful how much has been 

 achieved up to this time. 



As regards direct observation, with the aid of very high magni- 

 fying powers, upon animal tissues, a department of microscopical 

 work which has engaged much of my attention during many 

 years, I would remark that many observations have been made 

 upon the structure and arrangement of the most delicate nerve- 

 libres less than the hundred-thousandth of an inch in diameter, 

 and other tissue-elements of very small insects. With due care, 

 facts are ascertained which could not have been demonstrated 

 with the aid of object-glasses magnifying less than from 2500 to 

 3000 diameters. Not only is the demonstration of structure and 

 arrangement satisfactory, but in many cases a conception of the 

 action and working of the textures during life has been formed, 

 which would not otherwise have been obtained. The exact 

 relation of certain delicate nerve-fibres to the living matter of the 

 nerve in special organs has been determined, and many elementary 

 facts necessary for the determination of the changes constituting 

 nerve action have been ascertained. 



To my mind, however, the study, with the aid of high powers 

 and various improved means of examination, of the phenomena 

 which occur in living matter during life, transcends in importance 

 at this time all other inquiries in which the Microscope takes 

 a leading part. For these changes characterize every form of 

 living matter at every period of its being, and in every condition of 

 health and disease. In every form of living matter which exists or 

 has ever existed the great mystery of life and death is enacted 

 under our very eyes, but we have not yet been able to discover the 

 exact nature of the change, though we can prove most con- 

 clusively that it is not merely mechanical or chemical, as some 

 pertinaciously insist. No chemist or physicist has been able to 

 explain the changes which do occur, or has succeeded in imitating 

 them out of the living body. The most diverse structures and the 

 most widely different chemical compounds are produced by changes 

 occurring in particles of living matter which could not be dis- 

 tinguished from one another, and which are equally devoid of 

 colour and structure. Many of the current theories on the nature 

 of vital phenomena are not in advance of some that were pro- 

 pounded two thousand years ago ; and yet men occupying high 

 scientific positions are found to defend them, and to repeat again 

 and again statements concerning the relation between the living 

 and non-living, which are at variance, not only with facts familiar 

 to every one, but are contradicted by the experience and knowledge 

 every person possesses concerning certain vital phenomena of his 

 own organism. 



