[ 38 I 
LXXXV1IL 
That the Will does exert itfelf after this manner, 
is in a good meafure -proved by Dr. Stuart’s * Ex- 
periment upon a Frog, where a proper Impuife be- 
ing given to the Medulla fpinalis did excite Motion 
in the voluntary Mufcles, though the Head was fe- 
ver'd from the Body, 
LXXX1X. 
Hence alfo it appears, that the Nerves arc always 
replete with a fubtil Eluid capable of contra&ing 
the Mufcles, or other wife fuch an Impuife on the 
Beginning of the Nerves, could not have excited 
Motion after the Head was cut off. 
XC. 
And again, common Experience allures us, that 
tho* the Nerves are always replete with an athereal 
Medium ^ et this Medium, in a State of Health, never 
flies out at their Extremities, into the mufcular Fibres, 
without fome Impuife by the Direction of the Will*: 
Whenever it happens to do fo, Convulfions and 
Cramps are the natural Confequences. 
XCL 
* lectures on Mufcular Motion, 
