on Mufcitlar Motion. 2 $ 
mention the increafe at times of the circulation, and all the 
motions of the fluids without the leaft new motion in the fur- 
rounding bodies, or interference, or even knowledge of the 
mind. This motion muft therefore be original, and not com- 
municated. 
In communicated motion, if one body be at reft, and a mo- 
tion be communicated to it by another, the power of the whole 
motion fhall not be greater than that in the communicating 
body at the time of the communication. If I take out the 
heart of an animal, cut oft' the auricles, it will in many cafes 
continue to contraCt and dilate for fome time. If it be left to 
come to reft, and if foon after a needle be introduced into the 
ventricle, placed tranfverfely, and if the interior furface of the 
ventricle be pricked gently by the needle, the ventricle will 
contract with fuch power as to force the needle deep into it : 
in this cafe, the force of the contraction of the ventricle is 
much greater than the power with which it was pricked by 
the needle; this contraction was therefore not communicated 
to it by the moving needle, but was generated, and therefore 
an original motion. 
In all communicated motion, by which two bodies at a dis- 
tance are brought near to one another, there muft fublift fome 
other matter, by which they may be drawn, or forced, nearer 
to one another ; but in original motion, it is not at all neceflary 
that any other matter fiiould exift at all. Two particles, 
placed at as great a diftance from one another as the fun is from 
the earth, as has been already obferved, although at perfeCt 
reft, would begin to move nearer one another, by the attraction 
of gravitation, if all other matter whatever were annihilated. 
Moft authors who have treated on mufcular motion have 
fuppofed, that it was a communicated motion ; and that it was 
You LXXVIII. E produced 
