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 foregoing Part, considered the facts of structure. 

 As, hitherto, we have concerned ourselves with those most 

 general phenomena of organic form which, holding irre- 

 spective of class and order and sub-kingdom, illustrate the 

 processes of integration and differentiation characterizing 

 Evolution in general ; so, now, we have to concern ourselves 

 with the evidences 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 



