262 THEORY OF DISEASE. 



again rises ; that far more heat is removed by means 

 of ice than if we were to surround the head with a 

 bad conductor of heat. There has obviously been 

 liberated in an equal time a far larger amount of 

 heat than in the state of health ; and this is only 

 rendered possible by an increased supply of oxygen, 

 which must have determined a more rapid change 

 of matter. 



The self-regulating steam-engines, in which, to 

 produce a uniform motion, the human intellect has 

 shewn the most admirable acuteness and sagacity, 

 furnish no unapt image of what occurs in the animal 

 body. 



Every one knows, that in the tube which conveys 

 the steam to the cylinder where the piston-rod is 

 to be raised, a stop-cock of peculiar construction 

 is placed, through which all the steam must pass. 

 By an arrangement connected with the regulating 

 wheel, this stop-cock opens when the wheel moves 

 slower, and closes more or less completely when 

 the wheel moves faster than is required for a 

 uniform motion. When it opens, more steam is 

 admitted (more force), and the motion of the ma- 

 chine is accelerated. When it shuts, the steam is 

 more or less cut off, the force acting on the piston- 

 rod diminishes, the tension of the steam increases, 

 and this tension is accumulated for subsequent use. 

 The tension of the vapour, or the force, so to speak, 

 is produced by change of matter, by the combustion 

 of coals in the fire-place. The force increases (the 



