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CHAPTER VIII. 



THE DOCTRINE OP FINAL CAUSES IN PHYSIOLOGY. 



Sect. 1. Assertion of the Principle of Unity 

 of Plan. 



WE have repeatedly seen, in the course of our 

 historical view of physiology, that those who 

 have studied the structure of animals and plants, 

 have had a conviction forced upon them, that the 

 organs are constructed and combined in subser- 

 vience to the life and functions of the whole. The 

 parts have a purpose, as well as a law ; we can 

 trace final causes, as well as laws of causation. This 

 principle is peculiar to physiology; and it might 

 naturally be expected that, in the progress of the 

 science, it would come under special consideration. 

 This accordingly has happened; and the principle 

 has been drawn into a prominent position by the 

 struggle of two antagonist schools of physiologists. 

 On the one hand, it has been maintained that this 

 doctrine of final causes is altogether unphilosophi- 

 cal, and requires to be replaced by a more compre- 

 hensive and profound principle : on the other hand, 

 it is asserted that the doctrine is not only true, but 

 that, in our own time, it has been fixed and deve- 

 loped so as to become the instrument of some of 



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