[ 61 ] 
whereby they are reduced to oblong Forms, and the 
whole Mufcle is drawn beyond its Tone of Reft. 
XXIX. 
It is thus alone the (^/Equilibrium is altered be- 
tween two Antagonifts in an Inftant, without a Ne- 
ceflity of taking one Drop of Blood from the one 
to add to the other : And it is even fo far from it, 
that, during all this ACtion, the Quantity of Blood 
in both Mufcles, while one is contracted, and the 
other dilated, is nearly equal ; for altho’ the Blood 
is flopped in the aCting Mufcle, by the Mechanifm 
above explain'd, and the Veins are ail compreftfed, fo 
as to contain none during a violent Contraction ; yet 
the Arteries may be faid to contain a double Quan- 
tity, propelfd into them by the conftant Pulfe, as 
they are elaftic, while the Circulation is carried on 
pretty equally in the Antagonift ; and confequently 
both Arteries and Veins in this can contain no more 
than the very Arteries in that : Therefore a Mufcle is 
neither larger not lefs, in general, by Contraction 
or Extenfion, than when in a State of Reft, the Pro- 
portion being conftantly kept up; that is, when 
Ihorter, a little thicker ; when longer, a little more 
flender. 
XXX. 
Our Explanation of the Equilibrium between 
the interftitial Air, and the mulcular Cells , will ena- 
ble us to attempt accounting for the fwifreft gentle 
mufcular Motions that can be perform'd ; fuch as are 
ncceflary in an Allegro Part on an Inftrument of 
Millie, 
