286 
CONTAGION AND MIASMS. 
mere reproduction, namely, the idea of an active power, 
exercised by virtue of a def?iite form , and production and 
generation in a definite form. By chemical agency, we can 
produce the constituents of muscular fibre, skin, and hair, 
but we can form by their means no organized tissue, no 
organic cell. The production of organs, the co-operation of a 
system of organs, and their power not only to produce their 
component parts from the food presented to them, but to 
generate themselves in their original form, and with all their 
properties, are characters belonging exclusively to organic 
life, and constitute a form of reproduction independent of 
chemical forces which are subject to it. The vital principle 
is only known to us through the peculiar form of its instru- 
ments, that is, through the organs in which it resides. 
Hence, whatever kind of energy a substance may possess, if 
it is amorphous and destitute of organs from which the 
impulse, motion, or change proceeds, it does not live. Its 
energy depends, in this case, on chemical action. Light, 
heat, electricity, and other influences may increase, diminish, 
or arrest this action, but they are not its efficient cause. In 
the same way, the vital principle governs the chemical powers 
in the living body. All substances used for food are chemical 
compounds, and it is only, therefore, the chemical powers by 
which their constituents are held together, that the vital 
principle has to overcome. It opposes to the continual action 
of the atmosphere, moisture, and temperature upon the 
organism, a resistance which is, in a certain degree, invincible. 
It is by the constant neutralization and renewal of these 
external influences that life and motion are maintained. 
“ The greatest wonder in the living organism is the fact that 
an unfathomable wisdom has made the cause of a continual 
decomposition or destruction, namely, the support of the 
process of respiration, to be the means of renewing the 
organism and of resisting all the other atmospheric influences, 
such as those of moisture and changes of temperature. 
“All the supposed proofs of the vitality of contagions, are 
merely ideas and figurative representations, fitted to render 
the phenomena more easy of apprehension by our senses, 
without explaining them. These figurative expressions with 
which we are so willingly and easily satisfied in all sciences, 
are the foes of all inquiries into the mysteries of nature ; they 
are like the fata morgana , which show us deceitful views of 
seas, fertile lands, and luscious fruits, but leave us languishing 
when we have most need of what they promise.” — From 
Food's Lectures on Chemistry . 
