344 ESSAYS any OBSERVATIONS 
the infenfibility with which this organ is 
affected *, 
(v) StncE opium foon puts a ftop to 
the vital motions of animals, which yet 
continue in time of fleep with little or no 
diminution of their vigour; fince it often 
eafes pain without bringing on fleep, and 
‘fince, by its topical action on the heart, 
it deftroys the motion of this organ after 
all communication between it and the 
origin of the nerves is cut off f; it fol- 
lows, that the effects of opium are not 
owing, as fome have thought, to its pro- 
ducing fleep: On the contrary, the fleep 
which it occafions, feems to be only a 
confequence of its impairing the fenfibi- 
lity of the whole nervous fyftem. 
THE other effects of opium may be al- 
fo deduced from the fame caufe, particu- 
larly its reftraining all evacuations that 
are 
*n frogs, into whofe ftomach and guts I had in- 
jected a folution of opium, | not only found the heart’s 
auricle, but alfo the great veins leading to it, much di- 
fended with blood. Vid, Eflay on vital motions, Xe. 
p. 371. and 372. 
'-} Vid. N° 42, 13. 17. 18, 19. & 20. above 
