HUMAI PHYSIOLOGY. 



BOOK SECOND. 



DYNAMICAL PHYSIOLOGY. 



COURSE OF LIFE. 



CHAPTER I. 



OF THE PRINCIPLE OF ORGANIZATION, OR PLASTIC POWER. 



Remarks on the Subdivision of Physiology. 



Career of an Organic Form. Three Modes of Development. 



Inquiry respecting the special Principle of Organization. Illustration from the Growth of a Plant 

 in Darkness and Light. Inference respecting Plastic Power : its Nature and Properties. 

 Of the ordinary Growth of a Plant, and the Sources from which its Materials are derived. 



Relation of all Organisms to each other. 



Correction of the Doctrine of a Plastic Power, from Considerations regarding the Individuality 

 of a Plant. Plants are Operations, not Individuals. Physical Illustration of this View. 



Conclusion respecting the Nature of the Plastic Power : that it is a continued Manifestation of an 



REGARDING physiology as a branch of natural philosophy, I have been 

 led in this work to introduce the methods of considering it Divisions of 

 which are familiar to writers on mechanics ; for, as there are physiology, 

 two distinct divisions of that subject, according as we treat of the equi- 

 librium or the motion of inorganic bodies, so likewise there must be in 

 physiology a statical and dynamical branch, the one including the con- 

 ditions of equilibrium of an organized form, the other those of its devel- 

 opment development being no more than its motion. 



If we establish this subdivision in physiology, similar advantages will 

 doubtless be obtained for this science as those which so Advantages of 

 quickly accrued to mechanics after Galileo had formally in- this division. 

 troduced the same partition therein. Moreover, in this case there are 

 collateral reasons not applying to that. Whatever may be the views 

 which the advance of science causes us to take of the various functions 

 maintaining a living animal in its normal state whatever may b the 



