220 
The Applications of Phijsiology 
I shall;, tliercfore, consider the subject more in detail, and base 
iny arguments, not on theoretical deductions, but upon facts oc- 
curring in your every-day experience. 
If I succeed in convincing you of the truth of these theories, 
then you are in a position to examine your own practice. If they 
do nothing more than explain the prmciples of your practice, this 
will still be of much benefit; for these principles being once 
known, you will be enabled to regulate it in a way best adapted 
for the purposes intended. Blindfolded Ignorance gropes with 
hesitating steps through " pastures new ;" but Knowledge steps 
boldly Ibrth, carrying along with her the lamp of Science to light 
her on her way. The duty of scientific men is only to show how 
practical applications may be made ; it is the duty of practical 
men to discover and make those applications. 
We have already explained that the heat of the animal body is 
supported by a combustion, or union with oxygen, of those con- 
stituents of food from which nitrogen is absent. But we have not 
yet considered the nature of the forces which exist in the body 
and produce its increase of mass, as well as occasion that waste 
for the restoration of which food is taken. It cannot be to sus- 
tain the heat of the body alone that a supply of food is requisite, 
for there exist in it other substances unfitted for the support of 
respiration, except under peculiar circumstances. What, then, 
are the ruling forces in the body by which its substance is in- 
creased or destroyed ? 
In every part of the animal organism resides the peculiar 
principle named Vitality. It is the cause of life, and is quite dis- 
tinct from the divine essence — the mind. Vitality is a power 
subject to laws such as govern other forces in the material world. 
For example, we can act upon the vitality of the finger by a 
blister or a hot iron, and can thus increase or diminish its intensity. 
The purpose for which this mysterious principle is implanted 
in the organism of an animal is to protect the matter of which its 
parts are composed from the action of the chemical forces. Matter 
is placed under the dominion of chemical affinity, whose constant 
aim is to produce new changes. It has a great desire to effect 
the total destruction of the Organic kingdom of nature, by making 
it pass into the Inorganic kingdom. Vitality is, therefore, im- 
planted in the animal organism to stand in antagonism to this 
power. 
The object of vitality is to sustain and increase the ma,;s of the 
body in which it resides; the object of the chemical forces is to 
destroy and waste that body. Vitality resides in every pait of the 
fortress which it has to defend : the chemical forces are encamped 
in the atmosphere which everywhere surrounds it. In fact, the 
chemical power is the gas oxygen, one of the principal constitu- 
