Bauhaus-Universität Weimar

OTHER INVOLUNTARY MOTIONS. 99 
queftions will fcarce be anfwered fatisfadorily, upon any fcheme of 
fympathy depending wholely on tlie communication or connection of 
nerves ; but have no difficulty in them, if the motions now mention¬ 
ed be referred to the mind or fendent principle. 
When, therefore, in confequence of a difagreeable fenfation in the 
lungs, arifing from the difficult paffage of the blood through their 
veffeis foon after expiration is finifhed, the infpiratory mufcles are 
contracted ; we are not to afcribe this to any unknown fympathy ad- 
ing mechanically upon thefe mufcles or their nerves ; but to the 
MIND or fendent principle, which being affected by the uneafy per¬ 
ception in the lungs, is thereby excited to increafe the action of the 
nervous influence upon the intercoflal mufcles and diaphragm ; by 
which the cavity of the thorax being enlarged, and the lungs infla¬ 
ted with frefh air, the difagreeable fenfation in them is removed ; 
and confequently the extraordinary contraction of the infpiratory 
mufcles ceafes : hence, by the re-action of the elaftic cartilages of 
the ribs, abdominal mufcles,&c. the cavity of the thorax is leffened, 
i. e. infpiration is naturally followed by expiration ; which again 
mufl foon be fucceededby a new infpiration, on account of the par¬ 
ticular fenfation which begins to arife in the lungs. 
3. It does not appear, that any effort of the mind or fendent 
principle is neceffary to expiration ; for this naturally takes place as 
foon as the mufcles of infpiration ceafe to ad. The re-adion of the 
cartilages of the ribs and flretched pericardium and peritoneum, are 
wholely owing to the elaflicity of the parts, and not to any mufcular 
contradion or additional force communicated to them at this time ; 
nay, the re-adion of the abdominal mufcles in expiration, feems to 
be pretty much of the fame kind * altho’ it is not improbable, that 
the extenfion of their fibres, by the depreffion of the diaphragm 
in infpiration, may, as a very gentle ßimulus, excite .in them a true 
mufcular contradion *. However, this irritation prompting the 
N 2 abdominal 
* 
* The fame thing may be faid of the fternocoßal’ mufcles, which are generally thought 
to pull the ßernum and cartilages of the ribs downwards and backwards in expiration, but 
which feem fcarcely, if at all to a&, in ordinary and gentle expiration.
        

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