22 THE DOCTRINE OF DESCENT. 
aversion in the higher consciousness of man and of the 
superior animals, till we see all reaction to external ex- 
citation dwindle into the scarce perceptible motions of 
the simplest protoplasmic animalcule, it is evident that 
there can be no question here of either consciousness 
or will, We cannot then separate the idea of those 
sensations of desire and aversion, by which mo- 
tions are excited, from the elementary attributes of 
matter, as we are wont to do with regard to the 
higher animals.’ 
In precisely the same sense, it was said some years 
ago by one of the most talented investigators of lan- 
guage—Lazarus Geiger, now unfortunately deceased :& 
“But how is it, if further down, below the world of 
nerves, a sensation should exist which we are not capa- 
ble of understanding? And it probably must be so. 
For as a body that we feel could not exist unless it 
consisted of atoms that we do not feel, and as we could 
not see a motion were it not accompanied by waves 
of light which we do not see, neither could a complex 
living being experience a sensation strong enough for 
us to feel it also, in. consequence of the motion by 
which it is manifested, if something similar, though far 
weaker and imperceptible to us, did not occur in the 
elements, that is to say, in the atoms. If we only con- 
sider that we are as little capable of knowing that the 
falling stone feels nothing, as that it does feel; it is 
fully open to us to decide, in accordance with the 
greatest probability, that the world is susceptible of 
explanation.” 
We have examined the limits which the investigation 
of nature has prescribed for itself. The organic world, 
