352 ^^ onvM. 



Effects of Respecting the second series of experiments, they are So 



Kyjn^^l^ conti'ary to all that repeated experience has taught, so con- 

 trary to the observations of Haller, Whytt and Munro, 

 Avho, notwithstanding the difference of opinion they held, 

 on some points connected with the operation of opium, 

 unequivocally agreed on this head, (viz. that it destroyed 

 the irritability) that I cannot but conjecture, some unob- 

 served circumstances must have diverted the usual accuracy 

 of Fontana from its natural bias. 



The conclusion drawn from the third scries of experi- 

 ments rests partly upon the accuracy of the second, and 

 partly upon the supposition that the heart has not any 

 nertes, which is concluded because the knife of the anato- 

 mist has not discovered them ; but except this opinion is 

 maintained upon some other ground, it can be considered 

 only as a peiiiio prtncfpii; the want of detection prores 

 nothing either way, as it is nothing more than an argument 

 of non-existence drawn from invisibility. Further, the ex- 

 periment proves too much ; the animal died instantaneously, 

 on the injection of thQ solution into the jugular vein; the 

 circulation nuist of course be interrupted ; by what means 

 was this sudden, this momentary effect communicated to the 

 distant parts of the animal ? 



I hare thus stated the proofs and arguments founded upon 

 them, adduced by Fontana, as accurately and at as ranch 

 length, as the limits of this paper will allow; let us now see 

 how the case stands when reduced to the test of experiment. 



Does Opium act npon the Irritability of the Muscular Fibre ? 



Exp. 1.*" The heart of a frog was immersed into half 

 an ounce of an aqueous solution of opium, in the propor- 

 tion of half a dram and six grains of opium to one ounce 

 of water, of the temperature of 44°, whilst contracting 

 25 times in a minute. Two minutes after immersion, it 

 contracted only 15 times in a minute: after 8 minutes the 

 contractions had ceased, and could not be excited again by 

 any mechanical stimulus. 



Exp.^A The heart of a moderate sized rabbit whilst 



* Vid. p. 5, Inaugural. Dissertat. Exp. 1. 

 t Vid. iuaug. Dissert, p. 7. Exp. 4- 



contracting 



