TRACTS OF THE LATERAL COLUMN.
The tractus lateralis or the lateral pyramidal tract extends as a robust bundle in the dorsal part of the lateral column. The termination of the fibres is in the anterior horn of the same side of the cord.
The tractus dorsalis or direct cerebellar tract lies at the periphery, lateral to the pyramidal tract. The fibres arise from the cells of Clarke's column, extend upward within the lateral column and pass, as a constituent of the restiform body, to the cerebellum, where they end within the anterior superior worm.
The tractus ventralis or Gmers' tract also lies at the periphery of the lateral column, in front of the direct cerebellar tract, and likewise ends within the cerebellum. The fibres take their origin from cells, on the same and the opposite side, which lie in the lateral part of the anterior horn and in the central field of the gray substance. They ascend at first with the direct cerebellar tract, do not, however, enter the restiform body, but continue as far as the pons, then enter the superior cerebellar peduncle and pass backward to the cerebellum, where they end within the anterior part of the superior worm (Fig. 74, fibrae arciformes).
The tradus or triangular bundle of Helweg is an additional small tract, which lies at the periphery of the lateral column, ventral to Gowers' bundle, and establishes relations between the spinal cord and the inferior olivary nucleus in the medulla oblongata. The source of the fibres has not been positively determined. They form, perhaps, an ascending tract, arising within the gray substance of the cord and ending in the olive; according to other views, the bundle conveys both ascending and descending fibres. The entire area of the lateral column included between the foregoing
tracts and the gray substance, belongs to the lateral ground bundle or fasciculus laleralis firofirius. Within this again appear numerous endogenous fibres, long and short associ ation fibres, which bind together various higher and lower lying segments of the spinal cord. The short fibres lie close to the gray substance and form the lateral boundary zone. In addition, within the lateral ground bundle are found the following sets of fibres: the tradus or Monakow's bundle, whose fibres descend from the nucleus ruber of the opposite side and lie within the cord medial to the direct cerebellar and ventral to the lateral pyramidal tract, partly within the field of the latter. The tradus lateralis, from Deiters' nucleus, passes somewhat more ventral. Medial to Gowers' bundle lies the tractus The fibres of this path are the axones of the commissure-cells of the cord, which pass through the anterior commissure to the opposite lateral column and there turn upward. The termination of the path is in the thalamus. The tractus consists of a fibre-strand, that accompanies the spino-thalamic tract and ends in the region of the corpora quadrigemina. The entire path is, therefore, also called the tractus et thalamicus. Approximately within the same field, the tractus lateralis descends from the quadrigeminal region; likewise, in the vicinity of the spino-thalamic fibres, the tractus descends as a path from the thalamus.