THE PHANTOMS BEHIND US 
always with us, but where are the myriad earlier 
forms that were the antecedents of the present animal 
life of the globe? True, the paleontologist finds a 
more or less disjointed record of them in the strati- 
fied rocks and sees in a measure the course evolu- 
tion has taken, but he does not actually see it at 
work as does the astronomer. More than that, the 
forces the astronomer deals with are mechanical 
and chemical, but the biologist deals with a new 
force called life that often reverses or defies me- 
chanical and chemical forces, but which is yet so 
identified and blended with them that we cannot 
conceive it apart from them. The stomach does not 
digest itself, nor gravity hold the blood in the lower 
extremities. The tree lifts up its weight of fluids 
and solids and holds aloft its fruit and foliage in 
spite of gravity; its growing roots split and lift the 
rocks; mosses and lichens disintegrate granite; vital 
energy triumphs over chemical and mechanical 
energy. 
Biological laws are much more subtle and difficult 
to trace and formulate than chemical and mechani- 
cal laws. Hence the student of organic evolution 
can rarely arrive at the demonstrable certainties in 
this field that he can in the sphere of chemistry and 
mechanics. It is very doubtful if life can ever be 
explained in terms of these things. Life works 
through chemical combinations and affinities, and 
yet is it not more than chemistry? It works with 
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