THE PROBLEMS OF PHYSIOLOGY. 243 



more conspicuous and important differentiations of functions 

 have arisen, it is as much as can be expected. 



§ 267. It will be best, for brevity and clearness, to deal 

 with these physiological problems as we dealt with the 

 morphological ones — to carry on the inductive statement and 

 the deductive interpretation hand-in-hand: so disposing of 

 each general truth before passing to the next. Treating 

 separately vegetal organisms and animal organisms, we will 

 in each kingdom consider: — first, the physiological differen- 

 tiations and accompanying changes of structure which arise 

 between outer tissues and inner tissues; next, those which 

 arise between different parts of the outer tissues ; and, finally, 

 those which arise between different parts of the inner tissues. 

 What little has to be said concerning physiological integra- 

 tion must come last. For though, in tracing up Morpho- 

 logical Evolution, we have to study those processes of inte- 

 gration by which organic aggregates are formed, before 

 studying the differentiations that arise among their parts; 

 we must, contrariwise, in tracing up Physiological Evolution, 

 study the genesis of the different functions before we study 

 the interdependence that eventually arises among them and 

 constitutes physiological unity. 



