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INTRODUCTION. 7 
>i 
Life being the most important of all the properties of be- 
ae, and. the highest of all characters, it is not surprising that 
‘it has in all ages been made the most general principle of dis- 
tinction; and that natural beings have always been separated, 
into two immense divisions, the /iving and the znanimate. 
Of Living Beings, and Organization in general. 
If, in order to obtain a correct idea of the essence of life, we 
consider it in those beings in which its effects are the most 
simple, we quickly perceive that it consists in the faculty pos- 
sessed by certain corporeal combinations, of continuing for a 
time and under a determinate form, by constantly attracting 
into their composition a part of surrounding substances, and 
rendering to the elements, portions of their own. 
‘Life then is a vortex, more or less rapid, more or less com- 
plicated, the direction of which is invariable, and which always 
carries . along molecules of similar kinds, but into which indi- 
' vidual molecules are continually entering, and from which they 
are continually departing; so that the form of a living body is 
f more essential to it than its matter. 
As jong as this motion subsists, the body in which it takes 
dine! is living—i¢ lives. When it finally ceases, it dies. 
After death, the elements which compose it, abandoned.to the 
ordinary chemical affinities, soon separate, from which, more 
or less quickly, results the dissolution of the once living body. 
It was then by the vital motion that its dissolution was arrest- 
ed, and its elements were held in a temporary union. 
All living bodies die after a.certain period, whose extreme 
limit is fixed for each species, and death appears to be a ne- 
- cessary consequence of life, which, by its own action, insensi- 
bly alters the structure of the body, so as to render its conti- 
» nuance impossible. 
, In fact, the living body undergoes gradual, but continual 
changes, during the whole term of its existence. At first, it 
increases in dimensions, according to proportions, and within 
“limits, fixed: for each Species and for each one of its parts 5 it 
then augments in density in the most of its parts:—it is this 
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