Biology Reference
In-Depth Information
5.3
Biological holism
The different kinds of biological holism include neo-vitalistic theo-
ries and theories of self-organisation. Neo-vitalistic theories are not
really fashionable any longer but their authors have often raised
pertinent questions, even if the answers they provided are poor. We
will therefore tackle these two types of holism in succession. Our
review will not be exhaustive, any more than it was for philosoph-
ical holism, but we shall try to define their general characteristics
in order to assess their ability to resolve the problem of molecular
non-specificity.
5.3.1
The neo-vitalistic holism of Hans Driesch
Hans Driesch (1867-1941), one of the pioneers of experimental
embryology, supported a vitalistic theory (Driesch, 1908, 1914).
Another pioneer in embryology, Roux, had, in an experiment on the
frog, destroyed one of the two cells of the embryo after the first divi-
sion, thus succeeding in inducing the development of half an
embryo. This seemed to confirm the theory of August Weismann
(1834-1914), the forerunner of genetic determinism, which postulated
the existence of a highly organised microscopic material structure in
the germinal cells that he called 'germinative plasma'. This structure,
which foreshadowed DNA, was thought to control embryonic devel-
opment in a very precise way, with each of its parts determining a
part of the adult organism. Weismann also imagined that the germi-
native plasma was split at each division of the cell. As each embry-
onic cell only received a portion, it could therefore only form one
specific region of the adult organism
26
corresponding to the portion
of germinative plasma that it had received. This theory easily
explained Roux's experiment. The surviving cell must have contained
only half of the germinative plasma relating to half the organism.
26
Unlike DNA, which is present in its entirety in each cell of the organism.
