ON OPIUM, 351 



2dly. Again,* Fontana immersed the hearts of various Effects of 

 animals immediately taken from the thorax, into a strong uvin^system^ 

 aqueous solution of opium, infusion of bark and simple 

 water, of equal temperatures, and found that these organs 

 were deprived of irritability, and that they ceased to con. 

 tract, or to be capable of being excited to contract, equally 

 soon on immersion into water as into a solution of opium 

 or infusion of bark. 



Sdly. He next injected an aqueous solution of opium into 

 the jugular vein of several rabbits, and found that it pro- 

 duced death instantaneously ; from this he concludes, as the / 

 heart is not furnished with nerves, and having proved that 

 the solution of opium does not exhaust the irritability of 

 the heart, that it must occasion death only by producing an 

 alteration in the condition of the fluids. 



The experiments with the 300 frogs, as related by Fon- 

 tana, I repeated, though upon a smaller scale, yet sufficient 

 to ascertain the truth of it. I followed the method de- 

 scribed by Fontana, and I found the fact to be correctly as 

 he relates it; the divided extremity of the crural nerves, 

 bared for the space of half an inch, and immersed in solu- 

 tions of opium of various degrees of strength, was not more 

 affected than if the same nerves had been immersed in water, 

 and the irritability of the muscles, to which they were dis- 

 tributed, was not in the least degree more altered. 



Although I admit the accuracy of these experiments, I 

 am inclined to call in question the sufficiency of them for the 

 purpose they were designed. There is a considerable differ- 

 ence betwixt the sentient and the divided extremity of a 

 nerve. This operation, even if the structure of the di- 

 vided part was capable of receiving and communicating im- 

 pressions, must in a great measure have had the effect of 

 destroying its sensibility, and though the solution was not 

 only applied to the divided extremity, but also enveloped 

 the surface of the nerve for a considerable distance, this 

 surface must also have lost in consequence of being sepa- 

 rated from the muscles by " scissars and pincers" so much 

 of the usual quantum of sensibility as to be unequal to 

 transmit any eifect produced upon it. 



* Fontana on Poisons, Vol, II. p. 352-364. French edition. 



Respecting 



