240 THE PHENOMENA OF MOTION 



of heat, an accelerated change of matter in the cooled 

 part. 



The resistance of the living tissues to the action of 

 oxygen is weaker at the cooled part than in the other 

 parts ; and this, in its effects, is equivalent to an in- 

 crease of resistance in these other parts. 



The momentum of force of the vitality in the parts 

 which are not cooled is expended, as before, in me- 

 chanical motion ; but the whole action of the inspired 

 oxygen is exerted on the cooled part. 



If we imagine an iron cylinder, into which we admit 

 steam under a certain pressure, then if the force with 

 which the particles of the iron cohere be equal to the 

 force which tends to separate them, an equilibrium will 

 result ; that is, the whole effect of the steam will be 

 neutralized by the resistance. But if one of the sides 

 of the cylinder be movable, a piston-rod, for example, 

 and offer to the pressure of the steam a less resistance 

 than other parts, the whole force will be expended in 

 moving this one side, that is, in raising the piston- 

 rod. If we do not introduce fresh steam (fresh force), 

 an equilibrium will soon be established. The piston- 

 rod resists a certain force without moving, but is raised 

 by an increased pressure. When this excess of force 

 has been consumed in motion, it cannot be raised high- 

 er ; but if new vapor be continually admitted, the rod 

 will continue to move. 



In the cooled part of the body, the living tissues 

 offer a less resistance to the chemical action of the 



