PRESIDENT’S ADDRESS. 3) 
and the circumambient medium in which it lives. Other similar films 
or membranes occur in the interior of protoplasm. These films have 
in many cases specific characters, both physical and chemical, thus 
favouring the diffusion of special kinds of material into and out of 
the protoplasm and from one part of the protoplasm to another. It 
is the changes produced under these physical conditions, associated 
_ with those caused by active chemical agents formed within protoplasm 
and known as enzymes, that effect assimilation and disassimilation. 
Quite similar changes can be produced outside the body (in vitro) by 
the employment of methods of a purely physical and chemical nature. 
It is true that we are not yet familiar with all the intermediate stages 
of transformation of the materials which are taken in by a living body 
into the materials which are given out from it. But since the initial 
processes and the final results are the same as they would be on the - 
assumption that the changes are brought about in conformity with the 
known laws of chemistry and physics, we may fairly conclude that all 
changes in living substance are brought about by ordinary chemical 
and physical forces. 
Should it be contended that growth and reproduction are properties 
possessed only by living bodies and constitute a test by which we may 
eae differentiate between life and non-life, between the animate 
Peet cdines and inanimate creation, it must be replied that no conten- 
of growth tion can be more fallacious. Inorganic crystals grow and 
ha multiply and reproduce their like, given a supply of the 
living and requisite pabulum. In most cases for each kind of crystal 
poe ving there is, as with living organisms, a limit of growth which 
; is not exceeded, and further increase of the crystalline 
matter results not in further increase in size but in multiplication of 
similar crystals. Leduc has shown that the growth and division of 
artificial colloids of an inorganic nature, when placed in an appropriate 
medium, present singular resemblances to the phenomena of the growth 
and division of living organisms. Even so complex a process as the 
division of a cell-nucleus by karyokinesis as a preliminary to the multi- 
plication of the cell by division—a phenomenon which would primd 
facie have seemed and has been commonly regarded as a distinctive 
manifestation of the life of the cell—can be imitated with solutions of 
a simple inorganic salt, such as chloride. of sodium, containing a 
suspension of carbon particles; which arrange and rearrange themselves 
under the influence of the movements of the electrolytes in a manner 
indistinguishable-from that adopted by the particles of chromatin in a 
dividing nucleus. And in the process of sexual reproduction, the 
researches of J. Loeb and others upon the ova of the sea-urchin have 
proved that we can no longer consider such an apparently vital 
phenomenon as the fertilisation of the egg as being the result of living 
