[33 1 
Thicknefs, when it abates in its Length ; and what 
Power can produce this Effect, but fuch a one as in- 
creafes the mutual Attraction between the condim- 
ent Particles £ 
LXXX. 
idly. Hence appears the Reafon, why the Belly of 
a Mufcle dwells during its Contraction, notwith- 
ftanding its Dimenfion in general is diminifh’d ,• for 
as the component Particles of each Fibre are more 
loofely join'd together about the Middle than to- 
wards its Extremities, which are generally tendinous, 
it is natural to fuppofe that the chief A&ion is between 
them ; that is, when a Fibre grows fhorter, fuch of 
its Particles which are mod at Liberty run nearer 
together, and as the Motion of all Bodies is ever 
in proportion to the Impuife they receive, and the 
Refidance they meet with, fo when the condiment 
Particles of the mufcular Fibres are drawn into a 
fhorter Compafs, by the means above-mention’d, 
the Middle of the Fibres mud dwell either inwardly 
or outwardly, or both, according to the Refiftances 
they meet with. 
LXXXL 
And laftly, Since the Coats of the mufcular Fi- 
bres do mod certainly grow thicker as they contrad 
in their Length, and yet the external Surface of the 
Mufcle in general is diminilhed 5 it manifedly fol- 
lows that their Cavities mud grow lefs, and their 
E & contain’d 
