770 THE NERVOUS SYSTEM 



their descent of the cord. The crossed pyramidal fibres course in the lateral column 

 ventral to Lissauer's zone, and lateral to the lateral fasciculus proprius, and form 

 the lateral cerebro-spinal fasciculus (crossed pyramidal tract). It is a large fas- 

 ciculus, oval shaped in transection, and since its axones terminate in the grey column 

 of the cord all along its length, it decreases in bulk as the cord is descended. 



In addition to the three dispositions of the dorsal root axones given above, cer- 

 tain of them, either by collaterals or terminal twigs, form end-brushes about the 

 cells of the nucleus dorsalis (Clarke's column). The axones given off by these cells 

 pass to the dorso-lateral periphery of the lateral funiculus, and there collect to form 

 the cerebello-spinal fasciculus (direct cerebellar tract of Flechsig). As such they 

 ascend without interruption, and in the upper level of the medulla oblongata pass 

 into the cerebellum by way of the inferior cerebellar peduncle or restiform body. 

 Necessarily, this fasciculus is not evident in levels below the extent of the nucleus 

 dorsalis. 



Also situated superficially in the lateral funiculus is another ascending conduc- 

 tion path, and, like the cerebello-spinal fasciculus, to which it is adjacent, it is also 

 in part at least a cerebellar connection. Its position suggests its name, super- 

 ficial ventro-lateral fasciculus (Cowers' tract). This tract at present does not 

 include as great an area in transverse section as when originally described. The 

 more internal portion of the original Gowers' tract is now given a separate signifi- 

 cance, and will be considered separately. While the exact location in the grey 

 column of all the cell-bodies giving origin to the superficial antero-lateral fasciculus 

 is uncertain, it is known that certain ventral horn cells contribute their axones to it. 

 Many of its cells of origin are scattered in the area immediately ventral to the 

 nucleus dorsalis, others in the intermediate and mesial portion of the lateral group 

 of ventral horn cells. In the lumbar region these cells are quite numerous, and, 

 therefore, the fasciculus begins at a lower level in the spinal cord than does the 

 direct cerebellar tract. In degenerations it becomes visible in the upper segments 

 of the lumbar region, and has been proved to increase notably in volume as the 

 cord is ascended. Its axones arise for the most part directly from cell-bodies of 

 the same side of the cord, though it has been shown by several investigators that 

 some of its axones come from the grey substance of the opposite side by way of 

 the ventral white commissure. Terminal twigs and collaterals of the posterior root- 

 fibres, mostly of the same side, but occasionally from the opposite side, terminate 

 about its cells of origin. At one time Gowers' tract was considered an entity, but 

 now, even in the more limited area it occupies, it must be considered a mixture of 

 axones of several terminal destinations or distinct neurone systems. The destina- 

 tion of some of its axones has not been determined with certainty. A portion go 

 to the cerebellum, and there have been traced to the cortex of the superior vermis. 

 Most of these reach the cerebellum not by way of the restiform body, as does the 

 lateral cerebello-spinal tract, but pass on in the brain-stem to the level of the infer- 

 ior corpora quadrigemina, and there turn back to join the brachium conjunctivum 

 or superior cerebellar peduncle. (Auerbach, Mott, Hoche.) Only a few of its 

 axones leave the fasciculus lower down in the medulla, to enter the cerebellum 

 by way of the restiform body, in company with the lateral cerebello-spinal tract. 

 (Rossolimo, Tschermak.) Another portion of its axones are thought to reach 

 the cerebrum, probably the nucleus lentiformis, though it has not been positively 

 traced further than the superior corpora quadrigemina. Many axones in Gowers' 

 tract of the cord correspond to those of the fasciculi proprii, and merely run 

 varying distances in the cord, to turn again into its grey substance. Schaeffer 

 followed some of these from the lumbar region up to the level of the second cervical 

 nerve. 



In the ventral border of Gowers' tract and immediately upon the periphery, 

 near the anterior lateral sulcus (exit of ventral nerve-roots), there is found in the 

 higher segments of the cord a small oval bundle, the olivary fasciculus or Helweg's 

 (Bechterew's) bundle. The functional direction of its fibres has not been settled. 

 It is asserted to be a connection of the olive in the medulla oblongata, and in the 

 cord is believed to be connected with the cells of the ventral column of grey sub- 

 stance, probably those of the lateral horn. By some observers it has been traced as 

 far down as the mid-thoracic region; by others, however, only as far as the third 

 cervical segment. The olives being nuclei largely concerned with cerebellar con- 

 nections, Helweg's fasciculus is probably an indirect cerebellar connection with the 



