PHYSIOLOGICAL INTEGRATION IN ANIMALS. 375 



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 con- 

 stituted mechanically-coherent wholes. Currying 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 those same actions by which bones, muscles, and ligaments 

 are specialized. But adequate treatment of this division of 

 the subject is at present scarcely possible. 



AVhat little of fact and inference has been above set down, 

 will, however, serve to make comprehensible the general truths 

 respecting which, in their main outlines, there can be no 

 question. Beginning with the feebly-differentiated sponge, 

 of which the integration is also so feeble that cutting off a 

 piece interferes in no appreciable degree with the activity 

 and growth of the rest, it is undeniable that the advance 

 is through stages in which the multiplication of unlike parts 

 having unlike actions, is accompanied by an increasing inter- 

 dependence of the parts and their actions ; until we come to 

 structures like our own, in which a slight change initiated in 

 one part will instantly and powerfully affect all other parts 

 will convulse an immense number of muscles, send a wave of 

 contraction through all the blood-vessels, awaken a crowd of 

 ideas with an accompanying gush of emotions, affect the 

 action of the lungs, of the stomach, and of all the secreting 

 organs. And while it is a manifest necessity that along with 

 this subdivision of functions which the higher organisms show 

 us, there must be this close co-ordination of them, the fore- 



