Abstract
We have used retrograde transport of horseradish peroxidase to determine the distribution of the preganglionic cell bodies whose axons join particular rami of the thoracic spinal cord in a series of guinea pigs, and in a small number of hamsters and cats. In contrast to other recent studies, our results show that the neurons sending axons to a ramus are confined to a single segment at the corresponding spinal level. This segmental organization supports the idea that the rostro-caudal position of preganglionic cell bodies is one determinant of selective synapse formation between preganglionic axons and sympathetic ganglion cells.