This series of concise essays on Enteroceptors is designed to interest
the gradu- ate student and to stimulate research. Even before the advent
of electrophysiological studies, classical physiological techniques had
shown the essence of the role of many of the enteroceptors. Thus the
monitoring influence of the cardiovascular mechanoreceptors on the heart
and on the systemic vascular resistance, the role of the arterial
chemoreceptors in hypoxia and the influence of the so-called Hering
Breuer stretch receptors on breathing had all been documented. The
pioneering work of ADRIAN, BRONK, ZOTTERMAN and others using
electroneurographic methods gave a remarkable impetus to the study of
the enteroceptors themselves. Nowhere is this better exemplificd than in
the case of the afferent end organs of the heart, the respiratory tract
and the abdominal and pelvic viscera. The remarkable development of our
knowledge of the multiplicity of types of nerve endings from the
thoracic and abdominal viscera acquired from electrophysiological
studies has refocussed our attention on the histological details of the
sites of such receptors. Once more research on the structural side has
been accelerated by the question raised by evidence obtained from
functional studies. This is well illustrated in the case of the carotid
body, where the long cherished belief that the innervated epithelioid
cells constitute the chemoreceptor complex is now under attack. The
detailed consideration of the functional characteristics of each entero-
ceptor considered has not occupied our whole attention.