614 IMPORTANT QUERIES. 



use of animal heat ? Is it not the essential cha- 

 racter of a vera causa, that its power should be pro- 

 portional to the effects it produces, and that the 

 latter should cease in its absence ? Is it philoso- 

 phical to assume the existence of any more causes 

 than are sufficient to explain the phenomena? 

 Or if an immaterial and unknown principle of 

 life be still admitted, will it explain anything in 

 the absence of caloric ? It is impossible to blink 

 these questions, or to resist the conclusion they 

 naturally force upon the common sense of every 

 unbiased mind, that caloric is not only the cause 

 of all excitement, but directly or indirectly, of 

 excitability that it is not only the most potent 

 and universal stimulant in nature, but the cause 

 of stimulability. 



Let us now proceed to trace the natural order 

 in which the different functions depend on each 

 other, and the manner in which all the organs are 

 united into one harmonious system. As it is al- 

 ready understood that the action of the heart is 

 owing to the same cause on which all the moving 

 powers of the animal economy depend, I shall 

 proceed to shew that it is derived from the lungs 

 by respiration, to which all the other functions 

 are subordinate, and not from an inherent pro- 

 perty of the muscular fibre, as maintained by 

 Haller ; nor from an inherent propulsive force, as 

 maintained by Tiedemann. 



It was long ago ascertained by Hunter, that 



