THE LAWS OF LITE. 251 



resistance. An excess of force overcomes the cohesion, 

 and destroys thereby the power of resistance. Too 

 hard a blow breaks a solid body : an excess of elec- 

 tricity rends a non-conductor. So, too intense a che- 

 mical action destroys vitality. May not putrefying 

 matters and some poisons act in this way ? 



Again : the resistance remaining the same, a given 

 motion produces entirely different results, according 

 to its amount or intensity. Thus, if a bullet be 

 projected against an open door with very little force, 

 its motion is stopped, a certain amount of heat is 

 generated, but the door remains unmoved : if it be 

 fired from a pistol, it passes through the door, which 

 still remains unmoved; but if it be projected with 

 an intermediate degree of force, the door is moved 

 upon its hinges. Much that is similar to this takes 

 place in the living body. 



The mere passive decay of a tissue designed for 

 use produces no vital action ; an unused muscle 

 wastes ; excessive or morbid decomposition may 

 equally fail to be followed by the nutritive process, 

 as when death ensues from prolonged over-exertion, 

 or atrophy from inflammation. Only an intermediate 



