1890.] The Persistence of Plant and Animal Life. 527 
effort to detect them, so that it is not at all unreasonable to con- 
clude that practically the whole category of elements forming the 
superior part of the earth’s crust, or floating as gases in the at- 
mosphere, is represented in this material. 
Under the conditions of temperature, actinism (or the chemi- 
cal effect of the sun’s rays), barometric pressure, and constitution 
of the atmosphere and soil, the organic beings of our globe draw 
on their protoplasm for certain elements in excess of others, be- 
cause under these conditions the decompositions and recomposi- 
tions which take place are suited to maintaining life ; but, should 
any or all of these conditions change ; should the barometric pres- 
sure caused by the attraction of gravitation increase or diminish ; 
should the proportion to each other of the constituents of the at- 
mosphere suffer any marked variation; in any of these cases the 
present equilibrium would be disturbed; the oxidation and de- 
oxidation of the materials now employed as the bases of organic 
structure would evolve and absorb too many or too few heat-units 
for the present system of life, and either this latter would change, 
giving rise to new animals and plants, or the materials which 
would be selected from the protoplasm for assimilation would be 
other than carbon and hydrogen, thus giving rise to different struc- 
tures, composed of different materials, and behaving differently to 
heat and cold and chemical reagents. 
In a paper on Animal Protoplasm, read before the Am. Phil. 
Soc., and printed in the AMERICAN NATURALIST in 18709, I con- 
sidered the effect of changes of this kind on animals, pointing 
out that life being incomprehensible except as we could measure 
or weigh the phenomena which accompanied it, and these phe- 
nomena being such as would naturally occur among the substances 
by which we are surrounded, there was nothing to preclude the 
idea of living things colder than frozen mercury or hotter than 
molten platinum. This is true of the plant as well. As long as 

9 It would be apposite here to refer to Crooke’sb iful 1 hypothesis a the evolasion o of 
the elements to show that each so d el 
tion of the same matter, made permanent by the peculiar conditions which Wna it | 
at its genesis, and that therefore in any 
single matter which constitutes all things. But this would lead us astray from he's argu- 
ment in 


