498 JOHN HUNTER. 



make up the history of our planet, are directly 

 in proportion to the heating power of the sun, he 

 would have recognised caloric as the cause of 

 motion, and as the grand instrument of the Deity 

 in all the revolutions of matter from the forma- 

 tion of mountains to the aggregation of crystals, 

 and the more complicated organization of living 

 bodies. Or had he known that the vital energy 

 of animals is directly in proportion to their 

 standard healthy temperature, he would not have 

 inverted this fundamental law of physiology. 



In the observations of Hunter on the animal 

 economy, he recommends to the attention of 

 philosophers a comprehensive inquiry into the 

 laws of heat, as connected with all the ope- 

 rations of nature. And he observes in his Lec- 

 tures on the Principles of Surgery, that " heat 

 must be regarded as one of the first principles of 

 action in nature, which unlocks matter, and 

 allows it to act according to its natural pro- 

 perties ; that it is congenial with the vital prin- 

 ciple, which owes its vigour to a due supply of 

 heat ; that it is a sign of strength in the consti- 

 tution, whereas coldness arises from weakness of 

 the whole constitution."* But I have shewn that 

 heat is not only the agent which unlocks matter, 



* Following in the footsteps of Hunter, Sir Gilbert Blane ob- 

 serves, that " the combination of heat with the conservative prin- 

 ciple, forms the main constituent of simple life." (Medical 

 Logic.) But, like the vis insita of Haller, the vis medicatrix 



