66 Dr. Philip’s experiments to ascertain the principle 
depends as immediately on the brain, as that of the latter does 
on the heart, others maintain, that the nervous power may be 
wholly destroyed without impairing the vigour of this organ. 
This point it is necessary to determine, before we can trace 
with precision the modus operandi of poisons. The following 
inquiry therefore may be divided into two parts. In the first, 
I shall endeavour to ascertain how far the power of the heart 
is influenced by the state of the nervous system ; in the other, 
by what steps certain poisons destroy the powers of both. 
This I shall reserve for another paper, and here confine my- 
self to the first part of the subject. 
Till the time of Haller, it seems to have been the general 
opinion, that the muscles derive their power from the nervous 
system. He taught, that the power of the muscles depends 
on their mechanism, that the nervous influence is merely a 
stimulus which calls it into action, and consequently that those 
muscles, the heart for example, which act only by the appli- 
cation of one peculiar stimulus, unconnected with the nervous 
system, are wholly independent of it. This opinion seemed 
confirmed by its being generally admitted, that the action of 
the heart continues after it is removed from the body, and 
that it cannot be influenced by stimulating the brain, or 
spinal marrow, or the nerves which terminate in it. Haller 
and his followers maintain, that there are two distinct vital 
powers, one of the nervous and another of the sanguiferous 
system. 
The supporters of Haller’s doctrine however, found many 
difficulties to contend with. The evident objections to it are, 
that the heart is influenced by affections of the mind, and that 
it is supplied with nerves. Various hypotheses have been 
