“Life is a wave,” says Tyndall, but does not one conceive of something, some force or impulse in the wave that is not of the wave?  What is it that travels along lifting new water each moment up into waves?  It is a physical force communicated usually by the winds.  When the wave dies upon the shore, this force is dissipated, not lost, or is turned into heat.  Why may we not think of life as a vital force traveling through matter and lifting up into organic life waves in the same way?  But not translatable into any other form of energy because not derivable from any other form.

Every species of animal has something about it that is unique and individual and that no chemical or physiological analysis of it will show—­probably some mode of motion among its ultimate particles that is peculiar to itself.  This prevents cross-breeding among different species and avoids a chaos of animal and vegetable forms.  Living tissues and living organs from one species cannot be grafted upon the individuals of another species; the kidney of a cat, for instance, cannot be substituted for that of a dog, although the functions and the anatomy of the two are identical.  It is suggested that an element of felineness and an element of canineness adhere in the cells of each, and the two are antagonistic.  This specific quality, or selfness, of an animal pervades every drop of its blood, so that the blood relationship of the different forms may be thus tested, where chemistry is incompetent to show agreement or antagonism.  The reactions of life are surer and more subtle than those of chemistry.  Thus the blood relationship between birds and reptiles is clearly shown, as is the relationship of man and the chimpanzee and the orang-outang.  The same general fact holds true in the vegetable world.  You cannot graft the apple upon the oak, or the plum upon the elm.  It seems as if there were the quality of oakness and the quality of appleness, and they would not mix.

The same thing holds among different chemical compounds.  Substances which have precisely the same chemical formulae (called isomers) have properties as widely apart as alcohol and ether.

If chemistry is powerless to trace the relationship between different forms of life, is it not highly improbable that the secret of life itself is in the keeping of chemistry?

Analytical science has reached the end of its tether when it has resolved a body into its constituent elements.  Why or how these elements build up a man in the one case, and a monkey in another, is beyond its province to say.  It can deal with all the elements of the living body, vegetable and animal; it can take them apart and isolate them in different bottles; but it cannot put them together again as they were in life.  It knows that the human body is built up of a vast multitude of minute cells, that these cells build tissues, that the tissues build organs, that the organs build the body; but the secret of the man, or the