The anterior external arcuate fibers (ventral external arcuate fibers) vary as to their prominence in different cases: in some they form an almost continuous layer covering the pyramid (brain stem) and olivary body, while in others they are barely visible on the surface.
They arise from the cells of the gracile and cuneate nuclei, and passing forward through the formatio reticularis, decussate in the middle line.
Most of them reach the surface by way of the anterior median fissure, and arch backward over the pyramid.
Reinforced by others which emerge between the pyramid and olive, they pass backward over the olive and lateral district of the medulla oblongata, and enter the inferior peduncle.
They thus connect the cerebellum with the gracile and cuneate nuclei of the opposite side.
As the fibers arch across the pyramid, they enclose a small nucleus which lies in front of and medial to the pyramid.
This is named the nucleus arcuatus, and is serially continuous above with the nuclei pontis in the pons; it contains small fusiform cells, around which some of the arcuate fibers end, and from which others arise.
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