( 12tS ) 
Some great Pliyficians obferving this, and that deprived 
by whatfoever Means of Communication with the external 
Air, we became inftantly extinft, have imagined, that in 
the Aftt of Infpiration certain purer parts of the Air mixed 
with the Blood in the Lungs, and was conveyed with it to 
the Heart, where it nourifh'd a fort of Vital Flame, which 
was the caufe of this, reciprocal MJius of the Heart. Others 
not quite fo grofs, rejefting an AUual Flame, have fancied 
that thefe fine Parts of Air mixing with the Blood in the 
Ventricles ot the Heart, produced an Ejfervefcence which 
dilated it. But thefe Fancies have been long fince exploded 
and condemned upon ample Gonvidion, and 'tis a Point 
yet undetermin d, whether any Air does mix with the Blood 
at all in the Lungs, ornot. 
But fuppofing that fome Air may iqfinuate it felf into 
the Pulmonary Vein, it can no other way dilate the Heart 
than by an Effervefcence in the Left Ventricle, which 
woud not dilate the Right. But this opinion is contra- 
dicted by Autopfe^ and too laborioufly confuted by others^ 
to be brought upon the Stage again here. 
There remains therefore only the grofs Body of the Ar^ 
moffhere toht CQn^iAtidi, which is undoubtedly the true 
, Autagonlfl to all thofe Mufcles, which ferve for ordinary 
Infpiration and the Conftridion of the Heart. This will 
appear more evidently, if we confider not only the Power, 
but the neceffity of its A&ion upon Animal Bodies^ as well 
as the want of other fuflScient Agents. 
The Heart is a Solitary Mufcle of very great ftrength, 
and the Inter coftal Mufcles and Diaphragm, which like wife 
have no Antagonifts, are a vaft additional Force, which 
muft be ballanc'd by the contrary aftion of fome equiva- 
lent Power or other. For, tho the Adion of the Inter- 
' Mufcles be voluntary, that does not exempt em from 
the condition of all other Mufcles ferving for voluntary 
Motion, which wou'd be in a State of perpetual contracti- 
on, notwithftanding any Influence of the Will, were it not 
for 
