THE BIOLOGICAL SCIENCES AXD MEDICINE. 335 



can be drawn between the two classes of phenomena. 

 ~No one can say where anatomical variations end and 

 tumours begin, nor where modification of function, which 

 may at first promote health, passes into disease. All 

 that can be said is, that whatever change of structure or 

 function is hurtful belongs to pathology. Hence it is 

 obvious that pathology is a branch of biology ; it is the 

 morphology, the physiology, the distribution, the setio- 

 logy of abnormal life. 



However obvious this conclusion may be now, it was 

 nowise apparent in the infancy of medicine. For it is 

 a peculiarity of the physical sciences, that they are in- 

 dependent in proportion as they are imperfect ; and it 

 is only as they advance that the bonds which really 

 unite them all become apparent. Astronomy had no 

 manifest connection with terrestrial physics before the 

 publication of the " Principia ; " that of chemistry with 

 physics is of still more modern revelation ; that of phys- 

 ics and chemistry with physiology, has been stoutly de- 

 nied within the recollection of most of us, and perhaps 

 still may be. 



Or, to take a case which affords a closer parallel with 

 that of medicine. Agriculture has been cultivated from 

 the earliest times, and, from a remote antiquity, men 

 have attained considerable practical skill in the cultiva- 

 tion of the useful plants, and have empirically estab- 

 lished many scientific truths concerning the conditions 

 under which they nourish. But, it is within the mem- 

 ory of many of us, that chemistry on the one hand, and 



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