20 ^ HISrORT of the SOCIETK 



and inteftines, the cavity of the abdomen, &c. is found to produce 

 convuHions, it appears probable, that in the latter cafes, as in 

 the former, the convulfions do not proceed from any action of 

 the opium on the nerves of the part to which we apply it, but 

 from its being received into the fanguiferous fyftem, and im- 

 mediately applied to the brain. The experiments which follow, 

 in the treatife, confirm this conjedlure. On comparing toge- 

 ther all the experiments there related, and thofe alluded to in 

 the introdudion, it appears, that the various efFedls of opium 

 on living animals may be divided into three clalfes. The firft 

 comprehending its adtion on the nerves of the part to which it 

 is applied, not differing efTentially from that of any other local 

 irritation. The fecond comprehending its efFeds on the heart 

 and blood-veffels ; that of increafing their action, when applied 

 in a fmall quantity ; and that of impairing, or altogether deftroy- 

 ing their power of adtion, when applied to them more freely. 

 The third comprehending its effeds, when immediately applied 

 to the brain; which, when the dofe is moderate, are impaired 

 fenfibility, languor, fleep ; when applied more fully, convul- 

 fions and death. In all its effedls on the living animal body, 

 opium has much, in common with other fubflances, but at 

 the fame time fomething in each peculiar to itfelf. It may 

 appear an omiflion, Dr Wilson obferves, that he has not ranked 

 among the effeds of opium, received into the fyflem, thofe 

 which it feems to produce on the mufcles of voluntary motion. 

 In fome of the foregoing experiments, the irritability of thefe 

 mufcles was found much impaired after death, although the 

 opium was not applied diredly to the mufcles themfelves. But 

 it appears, both from an experiment related in the Treatife, and 

 others alluded to, that the impaired irritability of thefe mirf- 

 cles is owing, not to any dired adion of the opium on them, 

 but to the violent convulfions excited in them, in confequence 

 of the opium being applied to the brain. 



The 



