210 THE INDUCTIONS OP BIOLOGY. 



power of perceiving, through his general sensations, those 

 neighbouring concussions of which the ears ordinarily give 

 notice. Blind people make hearing perform, in part, the 

 office of vision. Instead of identifying the positions and 

 sizes of neighbouring objects by the reflection of light from 

 their surfaces, they do this in a rude way by the reflection of 

 sound from their surfaces. 



We see, as we might expect to see, that this power of per- 

 forming more general functions, is great in proportion as 

 the organs have been but little adapted to their special func- 

 tions. Those parts of plants which show so considerable an 

 ability to discharge each others' offices, are not widely unlike 

 in their minute structures. And the tissues which in ani- 

 mals are to some extent mutually vicarious, are tissues in 

 which the original cellular composition is still conspicuous. 

 But we do not find evidence that the muscular, nervous, or 

 osseous tissues are able in any degree to perform those pro- 

 cesses which the less differentiated tissues perform. Nor 

 have we any proof that nerve can partially fulfil the duty of 

 muscle, or muscle that of nerve. We must say, therefore, that 

 the ability to resume the primordial community of function, 

 varies inversely as the established specialization of function; 

 and that it disappears when the specialization of function 

 becomes great. 



61. Something approaching to a priori reasons may be 

 given for the conclusions thus reached a posteriori. They 

 must be accepted for as much as they seem worth. 



It may be argued that on the hypothesis of Evolution, 

 Life necessarily comes before organization. On this hypo- 

 thesis, organic matter in a state of homogeneous aggregation 

 must precede organic matter in a state of heterogeneous 

 aggregation. But since the passing from a structureless 

 state to a structured state, is itself a vital process, it follows 

 that vital activity must have existed while there was yet 

 no structure: structure could not else arise. That 



