Galen: On the Natural Faculties by Galen
Chapter VIII
Erasistratus denies that the stomach exerts any pull in
the act of swallowing. That he is wrong, however, is
proved by the anatomical structure of the stomach--its
inner coat with longitudinal fibres obviously acts as a
_vis a fronte_ (attraction), whilst its outer coat
exercises through the contraction of its circular fibres
a _vis a tergo_ (propulsion); the latter also comes into
play in vomiting. The stomach uses the oesophagus as a
kind of hand, to draw in its food with. The functions of
the two coats proved also by vivisection. Swallowing
cannot be attributed merely to the force of gravity.