26 INTRODUCTION. LECT. I. 



Conclusions. We conclude, therefore: 



1st. That living beings have the general properties of all 

 the bodies of nature ; that these properties are influential 

 in the production of the phenomena proper to them ; and 

 that, consequently, we must not neglect or disregard them 

 when we attempt to explain these phenomena. 



2dly. That the great physical agents, caloric, light, elec- 

 tricity, and molecular attraction, act on living beings as well 

 as on all the bodies of nature, and that their action must 

 necessarily be influential in the production of the functions 

 peculiar to these beings. 



3dly. That these forces, when acting on organized mat- 

 ter, sometimes have their general mode of action modified, 

 and that this difference is owing to a diversity in the struc- 

 ture and chemical composition of organized bodies. 



4thly. That there are also in living beings phenomena 

 which we call vital ; that these are numerous and of the 

 highest importance, and that, in the present state of science, 

 we are unable to explain how their production can be in- 

 fluenced by physical agents, though the action of these be 

 modified by the organism. This is the reason that we have 

 a study, a science whose object is the physico-chemical 

 phenomena of living bodies ; as there is one for experimen- 

 tal physiology. The intimate and necessary connexion is 

 found in the third class of facts which we distinguished. 

 Organization modifies the action of physical agents, and 

 the study of these modifications requires the co-operation of 

 physics and experimental physiology. Do not forget that 

 we have formed a fourth class of phenomena of living beings, 

 which we have called vital. I term them vital phenomena 

 not vital forces, and indeed the difference is truly vital. 



If Newton had called the force which rules the wondrous 

 system of the celestial machine merely attraction, or attrac- 

 tive force, his name would long since have fallen into ob- 



