[i6] 
as it is nfcdfary, expand themfelves, and fly fwiftly 
into the flefliy Fibres ; and, having made their Impe- 
tus, recede into the Tendons, by turns. But, while 
thefe Animal Spirits pafs into the flefliy Fibres, at 
the proper InftinCt for performing the Motion, 
they meet with very a&ive Particles of another 
Kind fupplied by the Blood, which ferment toge- 
ther ,• lo that, from their Strife and Agitation, 
the flefliy Fibres, which were before lax and porous, 
are fill'd up, and are forced into Corrugations ; 
from which the Contraction of the Mufcle pro- 
ceeds. When the Contraction is finifh’d, the pure 
Spirits, which remain, recede, for the moft part, into 
the tendinous * Fibres, the other Particles remain- 
ing among the Flefh ; the Blood fupplying the Ex- 
pence of thefe, and the Nerves of the others. And 
as to the InftinCt or Difpofition to the Ordination 
of Motion, our Author thinks that to be produced 
by other Spirits , fent out from the Brain to the Muf- 
cles when Motion is requir’d, which, by their vari- 
ous Impulfe, ordain thofe Spirits, already placed in 
the Tendons, to different Motions either of Expan- 
fion or Recefs. This is the Scheme for the Perform- 
ance of Mufcular Motion, according to this learned 
Author; the chief Part of which is the Agency of 
Fermentation ; wherein there appears but very little 
Difference between this and the DoCtrine hid down 
by Dr. | Croune. There feems however fome Impro- 
priety 
* Here are clearly Dr. Croune’s three Kinds of Spirits ; thofe in 
the Mufcular Flejb , thofe of the Tendons , and thofe fent from the 
Brain ; befides the Fermentation they produce by meeting in the 
Belly of the Mufcle. 
