340 ESSAYS anp OBSERVATIONS 
cles or vi/cera of a frog, would not puta ftop 
to the heart’s motion fooner, or indeed fo 
foon, as decollation and the deftrudtion 
of its fpinal marrow, (No 4. and §. com- 
pared with No 8. and io.) Opium there- 
fore does not produce its effects, folely, ° 
by putting a ftop to the funtion of the 
brain and {pinal marrow, but its influence 
"reaches to the fibres of the mufcles them- 
felves, or to the extremities of the ner- 
vous filaments which terminate in them. 
WHEN I fay the influence of opium 
reaches to the nervous filaments which 
terminate in the mufcular fibres, it is not 
meant, that any effluvia or fubtile parts 
of the opium are tranfmitted to them 
(See mand o above), but that it deftroys 
their powers, by means of that fympathy 
which they have, through the brain or 
fpinal marrow, with the nerves to which 
the opium is immediately applied. 
(/) From the above experiments we 
may infer, that not only the power of vo- 
luntary motion in the mufcles, but alfo 
their irritability or power of motion, when 
{timulated, proceeds from the nerves, or 
is 
