[ St ] 
how the feveral Principles juft laid down are appli- 
cable to it. 
XX, 
The Force of the inflating Matter contained in 
the Cells , is only equal to the Force of the inter • 
ftitial Air , while the Mufcle is at Reft. This may- 
be called the peculiar (^/Equilibration of a Mufcle in 
itfelf j but, by the Impulfe of the Will on the Nerve, 
an additional Inflation is made to the Cells, and then 
their Force becomes fuperior to the interflitial Air 
Globules j and again becomes equal when that Im- 
pulfe ceafes, and the Mufcle is at Reft. But if, 
upon the Ceflation of that Impulfe in one Mufcle, 
there is an Impulfe made on the Antagonift at the 
fame time, in order to move it, then the Force of 
this interflitial Air in the ceaftng Mufcle, exceeds 
that of the inflating Matter in the Cells, comprefling 
their Sides, whereby they are lengthened beyond 
their Tone of Reft ; as we fhall more fully explain 
it, when we fpeak of the ^Equilibration between 
antagoniftic Mufcles. 
XXL 
From this Inflation , which is perform’d as quick 
as Thought, the Cells inftantly increafe in Diameter, 
and grow fhorter, comprefs the venal Canals, and 
obftruft them. Hence the Blood flops, and the 
Arteries, by Propulfion from the Heart, increafe in 
their 
