14 
THE CHANGES OF COMPOSITION WHICH TAKE PLACE IN BODIES. 
certain circumstances, shall be designated 
Dvovisionally, under the name of aptitude for 
life or plasticity. It is only extinguished 
when these matters are reduced to their ele- 
ments, as whenever fire is made to act upon 
them. Thus, when the manifestations of 
activity, called life, are done away with in the 
matters of the peculiar kind appertaining to 
organic bodies, and the chemical operations 
of the special nature which occur in them 
after deatli, that is, putrefaction and fermen- 
tation are established, these matters do not en- 
ter completely into the inorganic kingdom, but 
retain the power of putting on a new form, and 
of showing themselves adapted to the enjoy- 
ment of life. Death, then, or the extinction of 
the manifestations of life only bears upon or- 
ganic individuals, whilst the organic matters 
entering into the composition of these beings 
continue to be cajiable of taking on form and 
receiving life. 
XIX- The principal result of the com- 
parisons made between the composition of 
organic bodies and those of inorganic bodies, 
which comparisons are founded on observa- 
tions and researches in the chemical composi- 
tion of these bodies hitherto pursued, is that 
the former have peculiar matters, whicli we 
call organic, for their basis. The changes of 
composition which take place in bodies en- 
dued with life, ai-e not simply the effects 
of afSnities similar to those observed in brute 
or inorganic bodies ; they are the effects of 
affinities and forces of a special nature. Or- 
ganic matters are the only ones which exhibit, 
and for the greater period of time in a par- 
ticular state of aggregation and form called 
organization, the manifestations of activity 
which we designate by the name of life. They 
are accumulated at one time in bodies actually 
living, and life is manifested in them ; at 
other times they are exterior to living bodies, 
mixed with inorganic matters, and then only 
capable of living. In this latter state they 
may return to domain of living bodies, and 
into the tide of life, either in the shape of ali- 
ments, or, in a direct manner, by the aid of 
certain circumstances, as happens in sponta- 
neous generation. Purely chemical affinities, 
or the action of simple chemical forces, ap- 
pear, in the present state of our planet, to 
produce no organic combination or matter, 
such as albumen, gelatin, starch, gluten, &c. ; 
at least we possess no facts which go to sup- 
port the contrary opinion. None but organic 
bodies themselves are capable of introducing 
inorganic matters into organic combinations, 
of which respiration in particular and the 
nutrition of plants are examples. 
XX. If we extend our researches still fur- 
thei-, a question presents itself, namely, how 
organic matters, their different combinations 
and living bodies, are formed in our planet ? 
The solution of this problem passess the limit 
of our experience. Should we, however, wish 
to hazard an answer to it, we fall into the 
waste of conjecture, and are forced to erect 
hypotheses, which are but probable, and not 
at all certain. We suppose that organized 
bodies have existed in our planet from its 
commencement ; or else we admit that organic 
matters and living bodies have been produced, 
under certain circumstances, together with 
the elements and organic matters, by the ac- 
tion of general physical causes ; or. lastly, 
we conjecture that the substance of living bo- 
dies was primatively contained in water, as 
primitive organic matter, having the pro- 
perty of taking on the organic form, that it 
gave origin to organic bodies of very simple and 
varied kinds in consequence of circumstances, 
and that these bodies have passed successive - 
ly to more complicated forms, until at length 
the generative organs and their manifestations 
of activity having appeared in them, they were 
endowed with the faculty of preserving them- 
selves in a continuous manner, by means of 
generation, as separate species. 
XXI. Geology is opposed to the first hy- 
pothesis of the existence, in our jdanet, of 
living bodies from the first moments of its 
creation. Fossils are found only in the 
exterior crust, that is to say, in the su- 
perficial layers of the earth, the formation 
which is most recent, whilst there are none at 
all in the primitive earths. Consequently 
there was a time when no living being existed 
on the globe. Even supposing we admitted 
this hypothesis, we should still leave un- 
touched the question, how living bodies were 
formed! in as much as we could say nothing con- 
cerning the mode of origin of our planet and of 
the bodies which constitute it. In reference 
to this question, it matters little whether we 
declare for vulcanism, orneptunisrn, since the 
geologists are under the necessity of leaving 
the origin of fire and water without explana- 
tion, and the biologist is still less able to pro- 
nounce any opinion on that of living bodies. 
XXII. The dilliculties which occur in the 
second hypothesis, of the dependence of the 
production of organic matters and living bodies 
on the action of general physical forces, are 
that we are actually in want of facts which 
would authorize us to conclude analogically 
that organic matters and living bodies can 
proceed from inorganic matters, never having 
observedany thing similar, at least up to this 
day. Far from this being the case, living bodies 
are unable to produce, with inorganic sub- 
stances, the greater number of the materials 
which enter into their composition, and for such 
end they require the matter of other organic 
bodies,* which they introduce into themselves. 
Plants are nourished principal ly by the remains 
of dead vegetables or animals : animals like- 
wise presei've their existence by means of ve- 
getables, and even of other animals. 
XX III. 4’he most probable hypothesis is 
the third, viz., that the substance of organic- 
bodies existed primatively in water, as a mat- 
ter of a particular kind, and that it was there 
endowed w ith the plastic faculty, that is to say, 
with the power of acquiring, by degrees, dif- 
ferentsimple forms of living bodies, with the 
concurrence of the general influences of light, 
heat, and perhaps also of electricity, &c., and 
of then passing IVoin the simple forms to_ other 
more complicated, varying in proportion to 
the modification occurring in the external in- 
fluences until the point when each species 
acquired duration by the production and ma- 
nif estation of activity of the genital organs. 
