on the Living St/stem. 11 



perlence has taught, so contrary to the obser- 

 vations of Ilaller, Whytt and Munro, who, 

 notwithstanding the difference of opinion they 

 held, on some points connected with the ope- 

 ration of opium, unequivocally agreed on this 

 head, (viz. that it destroyed the irritability) that 

 I cannot but conjecture, some unobserved 

 circumstances must have diverted the usual 

 accuracy of Fontana from its natural bias. 



The conclusion drjiwq from the third series 

 of experiments rests partly upon thp accuracy 

 of the second, gnd partly upon the supposition 

 that the heart has not any nerve§, which is 

 concluded because the knife of the, anatomist 

 has not discovered them; but except this 

 opinion is maintained upon some other ground, 

 it can be considered only as a petitio principli ; 

 the want of detection proves nothing either 

 way, as it is nothing more than an argument 

 of non-existence drawn from invisibility. Fur- 

 ther, the experiment proves too much; the 

 animal died instantaneously, on the injection of 

 the solution into the jugular vein ; the circu- 

 lation must of course be interrupted ; by what 

 means was this sudden, this momentary effect 

 communicated to the distant parts of the 

 animal ? 



I liave thus stated the proofs and arguments 

 founded upon them, adduced by Fontana, as 



B2 



