Biology Reference
In-Depth Information
In the treatise
On the Nature of the Child
, Hippocrates also puts
forward a theory of embryogenesis which complements his theory of
heredity. In the first phase of embryonic development, purely phys-
ical and chemical processes are in action. Breath and heat, as he
understands them, play a preponderant role. After coitus therefore,
the seed from the two parents mixes “
…and gathers into one mass
which condenses as a result of the heat. Next, it acquires breath,
since it is in a warm environment”
(ONC 12.1)
.
The seed thus
acquires its own ability to respire. It is heated and “
As it inflates,
the seed forms a membrane around itself; for its surface, because of
its viscosity, stretches around it without a break, in just the same
way as a thin membrane is formed on the surface of bread when it
is being baked…
” (ONC 12.6). In the second phase, the tissues and
organs differentiate from this primitive embryonic structure by a
principle of spontaneous organisation. Attraction between like and
like draws identical parts together and unites them.
“As the flesh grows it is formed into distinct members by breath.
Each thing in it goes to its similar — the dense to the dense, the
rare to the rare, and the fluid to the fluid. Each settles in its appro-
priate place, corresponding to the part from which it came and to
which it is akin”
(ONC 17.1).
Finally, these theories of reproduction and embryogenesis cul-
minated in an approach to human physiology based on the princi-
ple of balance between the four humours. Hippocrates made
frequent use of botanical analogies. Each of the four humours has
its own source: the head for phlegm, the heart for blood, the gall
bladder for bile, and the spleen for water, and in the same way that
any plant draws its specific humour from the earth, each of the
sources draws its own humour from the stomach. The humours cir-
culate between their reservoirs and the body as needed and equi-
librium is established according to the principle of communicating
vessels. Disease arises from an imbalance in this relationship.
In this Hippocratic concept, the material continuity of the body
is ensured by cyclic processes alternating phases of sublimation of
