DR. PHILIP ON THE POWERS OF LIFE. 
367 
The latter evil can only be obviated by a careful study of the laws of sympathy in the 
vital system, and particularly by ascertaining what organs are most inclined to be af- 
fected by what others; for although the function of sympathy is, like other functions, 
influenced by causes peculiar to the individual, it is in a great degree regulated by 
principles, which more or less prevail in all*. 
From the facts just referred to we easily perceive the cause of the sympathy by 
which every part of each of the foregoing systems is capable of influencing every 
other. Each is regulated by a leading principle, and in consequence of this, under 
an influence by which the affection of anyone part tends to affect all others; because 
as all parts of each system both influence this principle, and are influenced by it, it 
necessarily follows that all must, through it, — that is, through the central organs of 
each system, which alone are the immediate organs of its leading principle,— feel the 
affections of each. Such, together with the laws I am now to consider, is the source 
of the function to which the term sympathy has been applied, a principle as I have 
just had occasion to observe, which perhaps more extensively than any other regulates 
the course of disease. 
As each of the preceding systems is formed into a whole by its leading principle* 
the relations which these systems bear to each other have a similar effect with 
respect to the whole frame ; for the affection of any one of its parts tends more or 
less, though much less powerfully than in the individual systems, to influence all 
others. The means by which the relation between the sensitive and vital systems, 
and consequently the most complicated functions are maintained, we are here to 
consider ; to some of them I have already had occasion to refer. 
WE have seen that the nervous power properly so called, the leading power in the 
vital system, is immediately under the influence of the sensorial power, the leading 
power in the sensitive system, and constitutes the medium through which all that 
part of our intercourse with the external world, by which the latter power influences 
it, is maintained. This therefore is the first bond of connexion to which I shall refer 
between the sensitive and vital systems. The second is the means by which the 
organs of both systems are maintained ; for, as I have already had occasion to observe, 
the sensorial has a dependence on the vital system, for the maintenance of its organs, 
as the vital, we shall find, has a more remote dependence on the sensorial system, 
for the maintenance of its organs ; the connexion thus established between them 
being increased by both systems equally depending for the maintenance of their 
organs on the muscular power and the powers of the living blood ; both of which 
are in their turn subjected to the nervous, and the former certainly, and the latter, 
we have reason to believe, through the nervous, also to the sensorial power. 
The sympathy which prevails through all parts of each system also contributes to 
the influence of these systems themselves on each other ; because the state of the 
* My Gulstonian Lectures. 
