UPON VITAL PHYSICS- 



No writer has more correctly expressed the usually re- 

 ceived opinions of physiologists, concerning vital forces, 

 than Dr. J. Hughes Bennett, in his " Outlines of Physiology" 

 (page 44) : 



" In studying the different phenomena (whether physical 

 or vital), physiologists are in the habit of using the term 

 force much in the same manner as it is used by the general 

 cultivators of science. Mechanics has its forces, such as 

 that of the lever ; Chemistry has its forces, like that of 

 affinity ; and Physical Sciences has its forces, like that of 

 attraction. Physiology, also, has its forces. It has been 

 supposed that, in the same manner, we have physical 

 attractions and repulsions. Then we have contractile, 

 nervous and generative forces. The idea of force, whether 

 in physics or physiology, as explanatory of phenomena, 

 must be regarded only as a theory, as a mental creation, 

 which we employ as a convenient term to satisfy that 

 intense desire of arriving at definite causes which is instinc- 

 tive in man. On the other hand, it is often employed to 

 express action which may be demonstrated and often 

 measured. In this sense, it is as applicable to the action 

 of the stomach, or of the liver, as it is to that of an electric 

 telegraph, or a steam-engine." In short, vital force is often 



