Biology Reference
In-Depth Information
several times in 'Lectures on the Phenomena of Life' since it is
because of this autonomy that the parts of the organism act on each
other and can organise themselves so as to function.
“Thus differentiated and specialised, the anatomical elements live
their private lives in the place they are assigned, each according to
its nature. (…) It is by the mediation of the interstitial fluids,
forming what I have called the 'milieu intérieur', that the solidarity
of the elementary particles is established, and that each one receives
the repercussions of the phenomena that take place in the others.
The neighboring elements create for the one under consideration a
certain ambient atmosphere, and it feels the changes in it, which
regulate its life”
(LPL p. 260).
In ontophylogenesis, cells are autonomous and adapt to the
internal environment in which they are situated, which is itself
dependent on the external environment. From this point of view,
therefore, the two theories concur perfectly. Ontophylogenesis how-
ever also explains how organisms become more complex as they pass
through the three stages described by Bernard.
An organism always depends on the DNA, the environment and
the past borne by the structure, although the relative influence of
each of these factors will have been modified during evolution. The
initial cell which gave birth to the ontophylogenesis process will
have been subjected, during its history, to an endless accumulation
of selective constraints which have progressively adapted its struc-
ture to more and more diverse environments, a process making it
extremely complex and robust. The possibilities offered to the ran-
dom set of molecules will have been reduced, owing to restriction
on the number of potential molecular combinations caused by the
increasing importance of structuring the cells, to the point where
today's organisms are identically reproduced with a limited number of
possible variations that are nevertheless sufficient to allow the cell
differentiation necessary for forming tissues. Bertrand Laforge sug-
gested a very simple diagram, from which we will draw inspiration
here, to illustrate how constraints may force a mechanism to behave
