Bauhaus-Universität Weimar

OTHER INVOLUNTARY MOTIONS. 8r 
if this were the cafe, why fhould not all the mufcles of the malleus 
be equally contracted by the fame found ? And why fhould thofe 
which ferve to flretch the membrane of the drum be excited into 
motion by acute founds, while the mufcle which relaxes it is only 
brought into action by grave ones ? As brute animals, upon the firfl 
perception of any noife, turn their external ears towards the place 
from whence it comes ; fo, at the fame time, they adapt their inter¬ 
nal ear to it ; the firfl of thefe motions cannot be denied to flow 
from their fentient principle actuated by the found > why then 
fhould we doubt that the latter proceeds from the fame caufe ? 
The motions of the mufcles of the internal ear, inconfequence of 
various founds, are not only unattended with any confcioufnefs of 
volition, but are altogether involuntary ; for we cannot move them 
except when found flrikes the ear, nor hinder them to acül when it 
does. 
SECT. VIIL 
Of the alternate motions of refpiration. 
RESPIRATION is that aélion whereby a certain quantity of air 
is alternately received into the lungs and expelled out of them: 
it confifls of infpiration and expiration. Infpiration, or the recep¬ 
tion of air into the lungs, is owing to the contraction of the inter- 
coflal mufcles and diaphragm, whereby the cavity of the thorax is 
both lengthened and widened ; for as the lungs, together with the 
heart, éfc. perfectly fill the cavity of the breafl, and as their exte¬ 
rior furface is every where contiguous to the pleura and diaphragm 
L it 
* Some authors contend, that the lungs are not contiguous to the pleura, and that, in the 
fpace between them, there is contained what they call internal air, the ufe of which in refpi¬ 
ration they endeavour to fhew ; but the arguments, upon which this opinion is founded, do 
not appear to be conclufive, and which I think 1 could eafily ihew, were it not foreign to our 
prefent defign ; nor is the authority of the illuftrious Morgagni fufficient to fupport that 
doâxine(tf), fince the belt anatomift may be deceived in making a fingle experiment, and fince 
we have the repeated experiments of fome of the other great anatomifts againfl him ; nay, 
in every dead body, where the integuments and intercoftal ~ufctes are carefully taken off, the 
lungs may be feen contiguous to the pleura. 
(<0 Adverfar. anat. $, animadver, 33. $.46, 
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