382 PHYSIOLOGICAL DEVELOPMENT. 



comes into relation with other nerves. And if there be any 

 parts of its peculiar molecular motion uncancelled by the 

 molecular motions it meets at this centre ; or if, as will prob- 

 ably happen, the average molecular motion which it there 

 unites to produce, differs from the average molecular motion 

 elsewhere; then, as before, there will arise a discharge along 

 another channel or nerve to another centre or ganglion, 

 where the residuary difference may be cancelled by the 

 differences it meets; or whence it may be still further 

 propagated till it is so cancelled. Thus there will be a ten- 

 dency to a general nervous integration keeping pace with 

 the differentiation. 



Of course this must be taken as nothing more than the 

 indication of initial tendencies — not as an hypothesis suffi- 

 cient to account for all the facts. It leaves out of sight the 

 origin and functions of ganglia, considered as something more 

 than nerve-junctions. Were there only these lines of easy 

 transmission of molecular disturbance, a change set up in 

 one organ could never do more than produce its equivalent 

 of change in some other or others; and there could be none 

 of that large amount of motion initiated by a small sensation, 

 which we habitually see. The facts show, unmistakably, that 

 the slight disturbance communicated to a ganglion, causes an 

 overthrow of that highly-unstable nervous matter contained 

 in it, and a discharge from it of the greatly-increased quantity 

 of molecular motion so generated. This, however, is beyond 

 our immediate topic. All we have here to note is the inter- 

 dependence and unification of functions that naturally follow 

 the differentiation of them. 



§ 309. Something might be added concerning the further 

 class of integrations by which organisms are constituted 

 mechanically-coherent wholes. Carrying further certain of 

 the arguments contained in the last chapter, it might be 

 not unreasonably inferred that the binding together of parts 

 by bones, muscles, and ligaments, is a secondary result of 



