DOI Page / Citation link:
https://doi.org/10.11588/diglit.4812#0102
g2 OBSERVATIONS ON THE
We should then have admitted, that two causes, of a disferent nature,
were capable of producing exadly the same effed, which is not, in general,
agreeable to the laws of nature.
We mould find other consequences arise from such an hypothesis, which
tend to weaken the credibility of it. For instance, if, in a sound animal,
the vis nervea alone produces the contraction of the muscles, we will ask
what purpose the vis insita serves ?
»
If both operate, are we to suppose that the vis nervea, impelled by the
mind or living principle, gives the order, which the vis insita executes,
and that the nerves are the internuntii, and so admit two wise agents em-
ployed in every the most simple adion ?
But, instead of speculating farther, let us learn the effects of experiment,
and endeavour from these to draw plain conclusions.
i. When I poured a solution of opium in water under the skin of
the leg of a frog, the muscles, to the surface of which it was applied,
were very soon deprived of their power of contradion. In like man-
ner, when I poured this solution into the cavity of the heart, by opening
the vena cava, the heart was almost instantly deprived of its power of mo-
tion, whether the experiment was performed on it fixed in its place, or cut
out of the body.
2. I opened the thorax of a living frog, and then tied or cut its aorta,
so as to put a stop to the circulation of its blood.
I then opened the vena cava, and poured the solution of opium into the
heart, and found not only that this organ was instantly deprived of its
powers of adion, but that, in a sew minutes, the most distant muscles of
the limbs were extremely weakened. Yet this weakness was not owing to
the
We should then have admitted, that two causes, of a disferent nature,
were capable of producing exadly the same effed, which is not, in general,
agreeable to the laws of nature.
We mould find other consequences arise from such an hypothesis, which
tend to weaken the credibility of it. For instance, if, in a sound animal,
the vis nervea alone produces the contraction of the muscles, we will ask
what purpose the vis insita serves ?
»
If both operate, are we to suppose that the vis nervea, impelled by the
mind or living principle, gives the order, which the vis insita executes,
and that the nerves are the internuntii, and so admit two wise agents em-
ployed in every the most simple adion ?
But, instead of speculating farther, let us learn the effects of experiment,
and endeavour from these to draw plain conclusions.
i. When I poured a solution of opium in water under the skin of
the leg of a frog, the muscles, to the surface of which it was applied,
were very soon deprived of their power of contradion. In like man-
ner, when I poured this solution into the cavity of the heart, by opening
the vena cava, the heart was almost instantly deprived of its power of mo-
tion, whether the experiment was performed on it fixed in its place, or cut
out of the body.
2. I opened the thorax of a living frog, and then tied or cut its aorta,
so as to put a stop to the circulation of its blood.
I then opened the vena cava, and poured the solution of opium into the
heart, and found not only that this organ was instantly deprived of its
powers of adion, but that, in a sew minutes, the most distant muscles of
the limbs were extremely weakened. Yet this weakness was not owing to
the