( 1218 ) 
This will appear more plain, if we confider the circum- 
ftances of it, and its motion, as a Mufcle^ with refpeft to 
other Mufcles. That Contraftion is the proper Adtion,. 
and ftate of all Mafcles, is evident front Experience of 
Fad, as well as Reafon. For, if any Mufcle bp freed from 
the power of its Antagonift^ it is immediately contraciecl^ 
and is not by any aftion of the Will, or Spirits to be re- 
duced to a ftate of Dilatation. Thus, if the Mufculi Flexo- 
res of any Joint be divided, the Extenfores of that Joint 
being by that means freed from the contrary Aftion of their 
Antagonifis^ that Joint is immediately extended without 
any confent'of the Will, and in that ftate it remains 3 and 
io Flce verf^ if the Extenfores be divided. From whence it 
is plain, that the Mufcles have no reftitutive motion, but 
what they derive from the Aftion of their Antagonijls by 
which they are ballanc'd. Thus likewife th^ SpwBers of 
the GhI a, Ams ^nd Vefica, having no proper Antagonijis^ 
are always in a ftate of Contraction, and fufTer nothing to 
pafs'em, but what . is forced thro em by the contrary Afti- 
on, of fome ftronger Mufcles, which, tho not properly to 
Q2i\Vdi Antagonijis^ yQt on all necellary occafions per- 
form the office of fuch. 
That the Heart is a Mufcle, furnifli'd and inftruded for 
motion like other Mufcles, is (in my opinion at leaft) de- 
monftrated beyond contradiftion by Dr Lower and others.. 
Arid, as it is 1 Solitary Mufcle without any proper Antago- 
^ijl, and not diredly under the power of the Will, nor 
exercifing f^/^;;/^^r; motion, it approaches neareft to the 
SphwSer k\nd\, which only has thefe conditions in common 
with ir. But in conftant and regular alternations of Con- 
traftion-and Dilatation, it differs exceedingly from all the 
Mufcles of the Body. 
This reciprocal JEjlus ofthe Heart has given the Learned 
abundance of trouble ^ who, finding nothing peculiar in 
tlie ftrud^ra^ neceflarily occafion ir, nor any 
