Reconstruction of axonal trajectory of individual neurons in the spinal cord using Golgi-stained serial sections

A procedure bringing the axonal and dendritic cut ends found in the confronting planes of the serial sections face to face by means of serial photomicrographs provides a means for precisely reconstructing individual Golgiimpregnated neurons. Utilizing this method, it was possible to follow at the caudal level of a kitten's spinal cord the total course of the axons and dendrites of sixteen intramedullary neurons. The neurons located in the dorsal horn (laminae IV and V) send their long ascending axon into the lateral funiculus of the ipsi- or contralateral side, and, in one case, into the anterior funiculus of the ipsilateral side, giving off on the way several collaterals to the dorsal half of lamina VII of the ipsi- or contralateral side. Some of the neurons found in the intermediate region and the ventral horn (laminae VII, VIII and X) distribute their axonal branches in the intermediate region or the ventral horn of the ipsi- or contralateral side or both sides, running throughout their course in the grey matter, while the others act in the same manner by way of the lateral or anterior funiculi. Axonal and collateral endings terminate with small terminal knobs. The total axonal length of the neurons observed, with the exception of some with a long ascending trajectory, varies from 1,680 mum to 6,480 mum.