( 1222 ) 
denary Atttty is a fort of Qeck or Couttterpolfe to it, and 
prevents an endeavour towards two contrary Aftions at 
once, which muft neceflarily fruftrate both^ For the Heart 
being a Springy, Comprejftble Body, whofe proper Aftion, 
which is Coatraftion, depends on the influx of certain Flu- 
ids into its Fibres, or Subftance 5 and containing befides a 
Fluid in its Ventricles^ or great Cavities, in one of which is 
the Mouth of this Artery, the aftion of this Veffel muft in 
great meafure refemble that of a Syringe^ whofe extremity 
is immersed in Water, the Enlargement or Expanfion of the 
Channels of the Artery ^^nfwering the drawing of the Em- 
i&(7///;5^, as the Conftriftive Motion of the Mufcle of the 
Heart does the Preffure of the Atmofphere upon the Surface 
of the Water, the one making way for the fluid, and the 
other forcing it to follow, where the refinance is leaft. In 
this fenfe we may allow a fort of Attraftion to the Puhio- 
nary Artery, depending wholly upon the Aftion of the 
iercojial Muibks and Diaphragm, which we mufl: therefore 
confefsto be very ferviceable and inftrumental in promoting 
the Syjiole of the Heart. 
But if the Learned Author be deficient in his account of 
the S)i(lok that is, if he has not obferv'd all the Mecha- 
nifm and Contrivance of Nature for the Contraftion of the 
Heart 5 much lefs fufEciently has he accounted for the Dia- 
ftole, or Dilatation of it, which he afcribes to a Motion of 
rejiimion of the over-ftrainU Fibres, which yet he con- 
felTes are made for ConJlriBion only. 'Tis true, he im- 
mediately after joyns the influx of the Blood as a concur- 
rent caufe 5 but from the flight notice that he takes of it, 
'tis plain, that he did not fo much as dream of any great 
fliare it had in that adion. His words are thefe. 
DeCorde ^iu (ut ohtter hoc moneam) cum omnk motus contraBi-- 
7^ oneperficiatur,&* Cordis Fihr£ ad conJlriSionem folumfa&a jint, 
apparet quoque Cordis motumiotxxm in Sy{!iQ\QpojitHm effe x^cumqi^ 
Fihr<ie ultra tonum fuum in omni conjlri^ione ejus tendantur^ 
idcirco uhi nixus ijle abfolvitur^ motu quafi reftitutionis Cor 
iter urn 
