NOT THE SOURCE OF ANIMAL HEAT. 31 



gastric juice are arrested, and an immediate check is 

 thus given to the process of digestion, so the paraly- 

 sis of the organs of vital motion in the abdominal 

 viscera affects the process of respiration. These 

 processes are most intimately connected ; and every 

 disturbance of the nervous system or of the nerves of 

 digestion re-acts visibly on the process of respiration. 



The observation has been made, that heat is pro- 

 duced by the contraction of the muscles, just as in a 

 piece of caoutchouc, which, when rapidly drawn out, 

 forcibly contracts again, with disengagement of heat. 

 Some have gone so far as to ascribe a part of the 

 animal heat to the mechanical motions of the body, 

 as if these motions could exist without an expendi- 

 ture of force consumed in producing them ; how 

 then, we may ask, is this force produced ? 



By the combustion of carbon, by the solution of 

 a metal in an acid, by the combination of the two 

 electricities, positive and negative, by the absorption 

 of light, and even by the rubbing of two solid bodies 

 together with a certain degree of rapidity, heat may 

 be produced. 



By a number of causes, in appearance entirely dis- 

 tinct, we can thus produce one and the same effect. 

 In combustion and in the production of galvanic 

 electricity w^e have a change of condition in material 

 particles ; when heat is produced by the absorption 

 of light or by friction, we have the conversion of one 

 kind of motion into another, which affects our senses 

 differently. In all such cases we have a something 



