DR. PHILIP ON THE POWERS OF LIFE. 
361 
motion of the blood in the capillaries continues unimpaired, and only fails in propor- 
tion as the supply from the large arteries fails the cause of the emptiness of the 
latter some time after death. 
By such means the materials on which the nervous influence operates are supplied 
and presented to it ; and the means of supply, namely, the power of the heart and 
arteries, as well as that of the capillary vessels themselves, being, as we have seen, 
under the immediate influence of the same power which effects the chemical changes-^, 
the supply is proportioned to the demand under the various conditions of the ever- 
changing functions ; and under the same influence are the means of removal, whether 
of secreted fluids or solid parts become unfit for the purposes of life. Such are the 
circumstances above referred to, which render it necessary that the muscles, whether 
directly or indirectly, employed in these functions should be subjected to the same 
power on which depend the functions of secretion and assimilation, namely, all muscles 
of involuntary propulsion, that is, with a very few exceptions, all muscles of invo- 
luntary motion. 
It appears from some lately ascertained facts that the secreted fluids are formed 
from the blood while still in its vessels, and not in the act of their separation by the 
secreting organs. That such must necessarily be the case appears from what has been 
said. The act of separation must be posterior to the changes effected by the chemical 
powers of the nervous influence. It is only while the blood is still in its vessels that 
it can be exposed to their operation ; and we have reason to believe that it is only as 
the due changes have been effected, that is, only as the secreted fluid has acquired 
its due properties, that it applies the due stimulus to the vessels by which it is dis- 
charged : on the same principle that the due action of the intestines, by which they 
discharge their contents, is not excited if these contents have not acquired their due 
properties by the chemical processes which take place in the stomach and duodenum. 
Such are the nature and functions of the nervous power, and its relations to the 
muscular power and the powers of the living blood. When we turn to the sensorial 
system, we find ourselves in a new world. Here voltaic electricity, which we so 
successfully substitute for the nervous influence, can do nothing. The immediate 
organs of the sensorial power, we have seen, are as it were hedged in and defended 
from contact with any of the agents of inanimate nature. 
On the one hand, we find the nerves of sensation, which so far partake of the nature 
of the external world, that they are capable of receiving and propagating impressions 
from its agents, but in all other respects are allied to the organs with which they are 
associated. By their vital powers they influence the immediate organs of the sen- 
sorium, and the functions thence resulting are the effects of one vital organ influencing 
* See a paper on the powers of circulation in the Philosophical Transactions for 1831 republished in my 
Inquiry into the Nature of Sleep and Death. See also my Inquiry into the Laws of the Vital Functions, Part II. 
t See experiments detailed in the Philosophical Transactions for 1815 and 1822, and my Inquiry into, the 
Laws of the Vital Functions, Part II. 
3 A 
MDCCCXXXVI. 
