The development of the dorsal funiculus in the human spinal cord.

1. The development of the dorsal funiculus of the human cord is described from the second month to the end of the fourth. 2. The fasciculus cuneatus arises as a distinct bundle of fibres near the mid-line in the ninth week. This gradually spreads laterally, and to it is joined the more medial fasciculus gracilis. 3. The original embryonic dorsal marginal layer is displaced laterally, and may possibly become the dorsolateral tract adjacent to the dorsal horn. 4. The appearance of the future 'epicritic' pathway is accompanied by a marked wave of differentiation in cervical and thoracic ganglia. 5. The implications of these findings are discussed in relation to the problems of peripheral and central factors in nervous development.