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The Body Electric
whole organism to the precisely engineered traceries of its microstruc-
ture. The DNA-RNA apparatus isn't the whole secret of life, but a sort
of computer program by which the real secret, the control system, ex-
presses its pattern in terms of living cells.
This pattern is part of what many people mean by the soul, which so
many philosophies have tried to explicate. However, most of the pro-
posed answers haven't been connected with the physical world of biology
in a way that offered a toehold for experiment. Like many attempts, the
latest major scientific guess, the morphogenetic field proposed by Paul
Weiss in 1939, was just a restatement of the problem, though a useful
one. Weiss conjectured that development was guided by some sort of
field projected from the fertilized egg. As the dividing cell mass became
an embryo and then an adult, the field changed its shape and somehow
led the cells onward.
The problem was that there were too many "somehows." Even if one
accepted Burr's largely ignored measurements of an electric L-field and
admitted that it might be the morphogenetic field (a possibility Weiss
dogmatically rejected), there was still no way of telling where the L-field
came from or how it acted upon cells. Nor was there an explanation of
how, if the field was an emanation from the cells, it could also guide them
in building an animal or plant. In applying the idea to regeneration,
biologists faced the related and seemingly insurmountable problem of
how a more or less uniform outflow of energy could carry enough infor-
mation to characterize a limb or organ. Given the complexity of biolog-
ical structures, this was even harder than imagining how a field could
"somehow" survive when the part it referred to was missing.
However, the morphogenetic field no longer has to account for every-
thing. Acceptance of dedifferentiation lets us divide regrowth into two
phases and better understand each. The first phase begins with the
cleanup of wound debris by phagocytes (the scavenger race of white
blood cells) and culminates in dedifferentiation of tissue to form a
blastema. Redifferentiation and orderly growth of the needed part con-
stitute the second phase.
Simplifying the problem in this way should give biologists an imme-
diate sense of accomplishment, for the first stage is now well under-
stood. After phagocytosis, while the other tissues are dying back a short
distance behind the amputation line, the epidermal cells divide and mi-
grate over the end of the stump. Then, as this epidermis thickens into
an apical cap, nerve fibers grow outward and subdivide to form individ-
ual synapselike connections the neuroepidermal junction (NEJ) - with
the cap cells. This connection transmits or generates a simple but highly