146 COSMIC PHILOSOPHY. [pt. jl 



way that none of the transmitted motion is allowed to 

 escape laterally. Ease of transit is here witnessed at its 

 maximum. 



Making use of these theorems of transcendental physics, 

 and applying to the problem his vast and accurate know- 

 ledge of biological details, Mr. Spencer has propounded a 

 theory of the genesis of nervous systems of all orders of 

 complexity, which, whether entirely or only partially true, 

 must be regarded as one of his most brilliant achievements. 

 In the lately-published " Physical Synthesis," which con- 

 eludes the first volume of his " Principles of Psychology," 

 Mr. Spencer shows that the iiTitability which characterizes 

 the entire surface of the lowest animals, and which probably 

 consists in the isomeric transformation of colloidal clusters of 

 molecules distributed over the surface, must gradually be- 

 come concentrated in certain definite transit-lines, just as the 

 circulation of a nutritive tluid becomes confined to certain 

 channels : while the collision of waves which takes place 

 wherever two or more of these transit-fibres inosculate, 

 must result in such chemical changes, and in the gradual 

 formation of such a structure, as characterize nerve-centres. 

 But the exposition, when carried into details, ig altogether 

 too abstruse to be profitably presented here, nor is it neces- 

 sary for our present purpose. The explanation of the laws 

 of association only requires that, starting with some kind 

 of nervous system as already established, we should examine 

 the character of the nutritive changes set up within it by 

 environing agencies. 



The foregoing argument shows us that the most prominent 

 characteristic of such changes is the formation of transit- 

 lines between neighbouring cells ; and we have seen that 

 the more frequently a wave of molecular disturbance passes 

 along any such transit-line, the more easily will it pass, and 

 the more difficult will it be to divert it into any other transit- 

 line. Hence in any complex aggregate of cells and fibres 



