This study of the arterial blood of the spinal cord indicates that, of the 62 radicular branches (rami radiculares), at the most seven or eight truly participate in the vascularization of the spinal cord. The authors have observed that the situation and distribution of these branches enable the distinction of three large arterial areas: cervicothoracic, midthoracic, and thoracolumbar. The fixed nature of the intramedullary arterial distribution contrasts with the variability of the afferent arterial supplies. No demarcation permits separation of the vascularization of the spinal cord into anterior and posterior parts. The anastomotic systems situated on the arterial pathways are potentially valuable, but their functioning is problematical. The anterior spinal artery is not continuous, for in the midthoracic region there exists a critical narrow zone. The perimedullary anastomotic system appears insufficient while intramedullary anastomoses are without functional value.