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Experiment ift. On the 4th of March, 1767, a 
kitten a week old, had its head cut off betwixt the 
firft and fecond vertibre of the neck ; the thorax 
was opened with all expedition, and the heart laid 
bare to view and obferved for fome time, that any 
difference might be eafier and more certainly noticed. 
After the animal ceafed to move its limbs, I touched 
the fpinal marrow with a probe, immediately the 
extremities of the animal were all ftrongly convulfed; 
but the heart alone feemed unaffeded, and continued 
to move without acceleration, or any degree of al- 
teration whatever. 
Betwixt this time, and the 10th of April, I re- 
peated the fame experiment upon half a dozen kittens 
ftill younger than the firft ; upon opening the thorax, 
the heart beat near 70 ftrokes in a minute. 
When the heart beat only 40 in a minute, or there- 
abouts, 1 began gently to touch the fpinal marrow 
with the point of a probe, and the limbs were im- 
mediately convulfed, but the heart not in the leaft 
affeded. 
I flit open both the ventricles of the heart, fo as 
to let out all the blood they contained ; and inftantly 
the heart ceafed to beat (though its pulfation con- 
tinues otherwife very long in animals fo young) : 
but the auricles which were not opened, and there- 
fore were ftill ftimulated with the blood, beat on. 
In this fituation, in feveral of thefe animals, I 
thruft the probe into the fpinal marrow ; but the 
heart neverthelefs continued in perfed reft, and 
inadion ; though, when its fubftance was pricked 
with the point of a knife, it might ftill be made to 
contrad. _ 
But 
