CHAPTER I. 



THE PROBLEMS OF PHYSIOLOGY. 



265. THE questions to be treated under the above title 

 are widely different from those which it ordinarily expresses. 

 We have no alternative, however, but to use Physiology in 

 a sense co-extensive with that in which we have used 

 Morphology. We must here consider the facts of function 

 in a manner parallel to that in which we have, in the fore- 

 going Part, considered the facts of structure. As, hitherto, 

 we have concerned ourselves with those most general pheno- 

 mena of organic form which, holding irrespective of class 

 and order and sub-kingdom, illustrate the processes of 

 integration and differentiation characterizing Evolution at 

 large; so, now, we have to concern ourselves with the evi- 

 dences of those differentiations and integrations of organic 

 functions which have simultaneously arisen, and which 

 similarly transcend the limits of zoological and botanical 

 divisions. How heterogeneities of action have progressed 

 along with heterogeneities of structure that is the inquiry 

 before us; and obviously, in pursuing it, all the specialities 

 with which Physiology usually deals can serve us only as 

 materials. 



Before entering on the study of Morphological Develop- 

 ment, it was pointed out that while facts of structure may 

 be empirically generalized apart from facts of function, they 

 cannot be rationally interpreted apart; and throughout the 



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