Study on the segmental supply of the sensory neurons and the origin of sympathetic postganglionic neurons innervating the meridian relative area is very helpful in elucidating the relation of meridian and viscera

in directing the clinical practice

and in studying on the essences of meridian. The distributions of cardiac afferent nerve have been more reported

but little is reported about the segmental nerve distribution over heart and pericardium meridian relative areas. In order to observe the orgins of innervation in the heart and pericardium meridian relative areas

we injected the 2o% HRP solution into some points of these two meridians in the upper extremities of l8 rabbits and lO Wistar rats. The results obtained were as follows. (1) The sensory labelled cells in these meridian relative areas were found between C5 and T2 spinal ganglions. The labelled cells innervating heart meridian relative area were comparatively concentrated in C7 - T1 spinal ganglions

and the labelled cells innervating the pericardium meridian relative area were comparatively concentrated in C6 - T2 spinal ganglions. These results indicated that the origins of these two meridian sensory innervation were roughly the same to the cardiac SegYnental innervation but had a relative differene. (2) The nember of the large labelled cells innervating these rneridian relative areas was evidently less than that of middle and small labelled cells. These resuIts show that the main afferent fibers distributing these two meridian areas are thinner nerve fibers

which innervate mainly vessels. It is suggested that the vessels and the nervous apparatus distributing vessels play an important role in somatic PSM. (3) The labelled sympathetic postganglionic neurons were mainly located ln the first two ganglions of the thoracic sympathetic trunk. This distribution was similar to the cardiac distribution of sympathetic Postganglionic neurons. These may be the therapeutic mechanism of acupuncture at the points of these meridians in the cardiac diseases.