102 THE president's ADDRESS. ' 



and the passage, under certain circumstances, of the corpuscles 

 throua^li the unrent walls. The results of Cohnheim's observations 

 and his theoretical conclusions, if established, might tend mate- 

 rially to modify our ideas as to the nature, if not as to the treat- 

 ment, of certain of the phenomena of various ailments to which all 

 of us are more or less liable. It is curious to note that similar 

 observations to those of Cohnheim were made many years ago by 

 Dr. A. Waller and Dr. Williams. But, as in other instances, 

 reimpoi'tation from Germany has secured for these observations 

 more attention than they received as native productions. 



You will object, I fear, that all these subjects are more imme- 

 diately interesting to myself than they can be to most of you. I 

 forbear, therefore, to go on with my list. 



I may, however, allude to a subject in quite another department, 

 which is open to the study of all, and which sooner or later will, 

 I think, assume a greater importance in its general bearings than 

 is, perhaps, at the present time supposed. I refer to the influence 

 which varying physical conditions exert upon not-living matter in 

 its transition from the fluid to the solid state — in other words, and 

 in illustration — the effects of temperature and moistui'e, and 

 viscidity of solution in modifying the process of crystallization 

 and the forms and structure of the resulting crystals. This 

 subject has been already very ably brought before us by Mr. 

 Hislop, and also by Mr Martin, on tlie part of Mr. Hookham, 

 and I think we have good reason to hope that we shall soon be 

 favoured with the results of the further observations and experi- 

 ments made by these gentlemen. 



I am naturally enough led on to another topic of the widest 

 interest. It is needless to remind you of the almost unlimited 

 field for research afforded by the myi-iads of plants and animals 

 revealed to us by the microscope, but of the very existence of which, 

 without the microscope, we should be ignorant. Everyone who 

 has had the opportunity, must have felt a peculiar kind of fascina- 

 tion in watching the changes and movements of these tiny but 

 wondrous organisms. Now, with regard to these organisms there 

 appears to have been, and still to be a too great tendency on the 

 part of microscopists to multiply species. But surely it is a better 

 thing to do, to show clearly developmental or other relation- 

 ship between two or more different forms, than simply to find some 

 hitherto undescribed form, and give to it a new specific or generic 



