t 37 1 
has not fo much made it his Bufinefs to account for 
the Manner in which this Fluid caufes the mufcular 
Fibres to increafe and fwell, in order to the Con- 
traction of the Mufcle, as to give the true Defcri- 
ption and Situation of the nervous Syftem ; than 
whom none has done it better. 
XL VII. 
And as to the Opinion of Dr. Robin fen concern- 
ing the <^/Ether, it can hardly give Satisfadion : For 
fuppofing this zyEther to be the Caufe of mufcular 
Motion, there mud be a Modus Adtionis to produce 
the necehary Effed; for it is not enough to fay a 
vibrating Motion caufes the Mufcle to contrad, with- 
out making fome Attempt to fhew in what Manner 
it does fo. We can underhand as much, by faying 
at once, The animal Spirits caufe the Mufcle to 
move 5 which was faid many Years ago. 
But, from a very natural and obvious Argument, 
one may venture to doubt, whether the z^/Ether 
can have any Share in mufcular Motion j for there 
can be no Motion, whatever, mechanically performed 
in One Body, without firfl receiving a certain Pro- 
pulfion from fomething elfe ; and the Body making 
that Propulfion ought to be endow’d with Qualities 
neceffary for fuch a Refinance, proportioned to the 
Body aided upon : Now', if the zyEther (as Philo- 
fophers have defin’d it) be a fubtile Matter pervading 
all fubhantial Bodies, of whatfoever Solidity, without 
Lett or Hindrance, it cannot be faid to caufe 
mufcular 
