352 
DR. PHILIP ON THE POWERS OF LIFE. 
world, and the same method which leads to a knowledge of other sciences must 
guide us here. There are no means but a study of its phenomena by which we can 
attain a knowledge of life, that is, of its properties, the only knowledge we can attain 
of any principle of action. But if our object be to attain a correct knowledge of it, 
we must first determine with accuracy what are the phenomena of life ; for, in the 
complicated functions of the living animal, it requires not a little patience, labour and 
circumspection to distinguish what part depends on vital powers properly so called; 
and what, on a modification of the powers of inanimate nature. Even the most cursory 
view must convince us that many of the functions of the living animal partake of the 
latter powers. 
Respiration is performed, that is the air is drawn into and expelled from the lungs, 
by means which act on the same principle as the bellows. The blood in the circula- 
tion moves on the same principle as the water in a set of water-pipes. It obeys a 
propelling force, and is subjected to the same laws of gravitation. The motion of 
our limbs is effected by the same mechanical laws, by which bodies are put in motion 
in the external world. Here, as in inanimate nature, velocity can only be obtained by 
the sacrifice of power. Similar observations apply to the various processes of secre- 
tion and assimilation. We can trace in these processes, the same chemical laws 
which obtain in the laboratory of the chemist ; but there is at the same time in all 
the foregoing functions something more in operation, analogous to which we find 
nothing in inanimate nature. 
The force indeed by which the air is drawn in and expelled in respiration operates 
on the same principle as in the bellows ; but the powers by which the machinery is 
worked are the contractile power of the muscular fibre, and the power of the nerves 
by which it is excited. The motion of the blood depends on the same principle as 
that of the water in its pipes, but it is the contractility of the muscular fibre which 
supplies the moving power. The same observation applies to the motion of the 
various members of our body. 
In like manner in the processes which maintain the organs of all these functions, 
and effect the separation of those parts of them which have become useless, and there- 
fore noxious, while we trace the same chemical laws which operate in other parts of 
nature, we can perceive that they are constantly modified by the powers peculiar to 
the living animal ; for it is not only impossible by any chemical arrangement to pro- 
duce the same results in inanimate nature, but even by the principles which regulate 
its phenomena, to trace all the steps by which they are effected. We can neither, for 
example, imitate the process by which the temperature of living blood is raised above 
that of the surrounding medium, nor, on the principles of the chemistry of inanimate 
nature, trace all its steps. No position can be more erroneous than that the chemical 
processes of the living animal depend alone on the same laws with those of inanimate 
nature. The properties of life are as peculiarly its own as the properties of gravi- 
tation. 
