Development of the glycogen body through the whole length of the chick spinal cord.
The development of the glycogen body was studied throughout the entire length of the chick spinal cord. The glycogen body cells first appeared at stage 31 on each side of the ependymal septum from the 26th to 28th segments of the spinal cord. by stage 34 the paired primordia of the glycogen body extended from the 25th to 29th segments. In the middle of the structure described classically as the glycogen body (i.e., the portion restricted to the level of the spinal nerves 26-29), these primordia were fused dorsally at stage 34 and had fused completely by stage 37. The paired primordia extended from the cervical enlargement to the lumbosacral portion of the spinal cord by stage 36 and extended to the upper cervical segments by stage 38. They were totally fused throughout the entire length of the spinal cord by stage 42. The glycogen-containin cells, in the classical glycogen body level, appeared ventrolateral to the central canal at stage 35. Thereafter they increased in number and glycogen content, and extended rostrad and caudad from the classical glycogen body level. They fused to each other and then fused with the glycogen body. Therefore, the bilateral clusters of the glycogen containing cells are considered as the ventral paired primordia of the glycogen body. The development of the glycogen body is essentially the same pattern as in the classical glycogen body throughout the entire length of the spinal cord.