374 
DR. PHILIP ON THE POWERS OF LIFE. 
leading power, which is both capable of influencing and being influenced by every 
part of it, is the cause of that powerful sympathy which exists among all its parts, 
and which we have seen often essentially influences either system with but little 
disturbance to the other, on which many of the most important phenomena of disease 
depend. 
THE muscular power, which has its seat we have seen in the muscular fibre itself, 
and the powers of the living blood, which have their seat in the blood itself, perform 
subordinate parts. They are equally employed in both systems for the maintenance 
of their organs. The latter supplies the materials endowed with the principle of life 
on which the nervous power operates in the formation of the secreted fluids, the 
maintenance of animal temperature and the various more immediate functions of 
assimilation ; while the former, to which the vessels as well as the heart owe 
their power, supplies the means by which these materials are duly exposed to the 
operation of the nervous power, by which their necessary changes are effected; 
that is, to the influence of the extremities of the nerves, by which the nervous power 
operates in all these functions, as well as in the excitement of the muscles ; for as 
the brain and spinal marrow, as we have seen proved by direct experiment, are the 
only parts of the nervous system employed in preparing the nervous influence ; the 
minute extremities of the nerves are the only immediate organs of its functions ; as 
the extreme parts of the sanguiferous system, the capillary vessels, are the organs by 
means of which the blood is immediately exposed to its influence. 
That the capillary vessels may be, as little as possible, influenced by adventitious 
causes in functions of such importance in the animal economy, we find on the one 
hand, as appears from experiments above referred to, that the motion of their blood 
depends wholly on their own powers, the larger arteries which depend for their 
supply of blood on the heart, being only the reservoirs from which they draw their 
supply ; and that, on the other, they are not controlled by the nervous influence 
through the medium of the heart, but receive this influence directly from its source : 
and so correct are these positions, that even the removal of the heart, if effected 
without considerable loss of blood, produces no immediate effect either on the action 
of the capillaries, or the control which the nervous power exercises over them. 
SUCH are the individual powers of the living animal, their seat, the relation they 
bear to each other, and the manner in which their several functions are effected. 
BUT the most complicated functions, it appears from what has been said, depend 
on the relations which subsist between the two systems themselves, into which the 
functions of all these powers are arranged. 
They are related to each other, we have seen, by the nervous, the leading power in 
the vital system, in consequence of the control exercised over it by the sensorial, the 
