Bauhaus-Universität Weimar

16 
OF THE VITAL AND 
ly contracted and dilated, without our being able/ by any effort of 
the will, directly to hinder or promote its motions. 
17. The contraction of the heart is, therefore, not only involun¬ 
tary, but of a different kind from that of the fphincters and mufcles 
deprived of antagonifts ; and feems, as to its appearances, to agree 
with the contraction of mufcles from aßimulus [14.]. 
18. The mind may, by difufe, not only lofe its power of mo¬ 
ving even the voluntary mufcles, except in a particular way, but 
alfo of exciting them into contraction at all. Of the former we 
have an example in the uniform motions of the eyes ; and of the 
latter in the mufcles of the external ear, and of fuch members as 
have remained long without motion. 
* 
SECT. II. 
An examination of the opinions of fome of the mofi confderable authors 
concerning the motion of the heart. 
IT feems to have been the prevailing opinion among many of the 
ancient phyfcians, that the motion of the heart was owing to 
a vital principle particularly refiding in it. Galen thought motion 
as natural to the heart, as reff to the other mufcles. Des Cartes, 
much lefs verfed in phyfiology than in mathematics, attributed the 
motions of this organ, wholely, to the ebullition of the blood drop¬ 
ping into its ventricles ; and contended, that this fluid was not 
pufhed into the arteries by the mufcular contraction of the heart, 
but that it forced its way into them by its own explofive power. 
After Harvey’s dodtrine of the circulation was fully eftablilh- 
ed, the heart was allowed to be a mufcle, and its fyftole to be 
analogous to the contraction of other mufcles ; the vital fpirits of 
the nerves were fuppofed to flow alternately into its fibres, either 
on account of valves, which by turns admitted and denied them 
a
        

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