Bauhaus-Universität Weimar

tpr- OF THE V I f A L AND 
tradlioiï, then indeed it might be fufpedled, that fuch motions were 
no more than a neceiTafy confeqitence of the mechanical action of 
thofe ßitnult upon the mufcukr fibres : but as we find the mufcles 
of animals brought into addon without any irritation of their fibres, 
whenever a ftimulus is applied to the coats or membranes covering 
them, to the nerves which are lent to them, or to fome neighbour¬ 
ing or even diftant part, it feems unreafonable to afcribe fuch mo¬ 
tion to tne mechanical addon of the ßitnulus upon the fibres of the 
mufcle, and not to the impreffion it makes on the fentient principle. 
Thus the contradlion of the fphinbler pupillæ arifing from the addon 
of light on the retina, with which it has no communication of 
nerves, cannot be explained mechanically, but mufl be owing to 
fome fentient principle in the brain, which, excited by the uneafy 
fenfation, increafes the addon of the nervous power upon that mu- 
fcle. The fame thing is alfo true of the various motions of the 
mufcles of the malleus and ftapes from different founds firiking 
upon the auditory nerve ; and of the motions of the eye-lids as of¬ 
ten as any thing irritates the cornea, be it ever fo gently. The con¬ 
tradlion of the diaphragm and intercoftal mufcles, in confequence 
of an uneafy fenfation in the lungs, mufl alfo be owing to the mind 
or fentient principle adling at the origin of the nerves, and not to 
any change wrought mechanically upon the fibres of thefe mufcles, 
by the difficult paffage of the blood through the pulmonary veffels. 
The violent addon of the diaphragm and abdominal mufcles in a 
ienefmus or flrangury is to be explained in the fame way. If a fpark 
from the fire, or a drop of boiling water falls upon one’s foot, the 
leg is inflantly drawn in towards the body ; but as the mufcles em¬ 
ployed in this adlion are thofe which run along the thigh, and are 
infected about the head of the tibia, it is manifefl that this flimulus 
cannot excite thofe mufcles into contradlion in confequence of any 
mechanical adlion upon them ; and if the fympathy of the nerves, 
or continuation of membranes, fhall be affigned as the caufe of this 
motion, it may be juflly afked, why the mufcles which run along 
the leg, and are inferted into the foot, are not more moved than 
thofe of the thigh, fince they have a nearer eonnedlion with that 


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