784 THE NERVOUS SYSTEM 



pyramids.' The remainder retain their ventral position in their descent decussating gradually 

 in the cord itself. The pyramidal fibres which cross in the medulla course in the lateral column 

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

 cerebrospinal fasciculus (crossed pyramidal tract). It is a large fasciculus, 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, 

 certain of them, either by collaterals or terminal twigs, form telodendria about the 

 cells of the dorsal nucleus (Clarke's column), which nucleus extends from about 

 the seventh cervical to the third lumbar segment of the cord. The axones given 

 off by these cells pass to the dorso-lateral periphery of the lateral funiculus, and 

 there collect to form the dorsal spino-cerebellar 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 con- 

 duction path, and, like the dorsal spino-cerebellar fasciculus, to which it is ad- 

 jacent, it is also in part at least a cerebellar connection. Its position suggests its 

 name, superficial ventre -lateral spino-cerebellar fasciculus (Gowers' 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 sig- 

 nificance, and will be considered separately. While the exact location in the grey column of all 

 the cell-bodies giving origin to the superficial ventro -lateral spino-cerebellar fasciculus is un- 

 certain, 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 seg- 

 ments 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 many 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 dorsal 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 destination of some of its axones has 

 not been determined with certainty. A portion, the spino-cerebeUar fasciculus proper, 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 dorsal spino-cerebellar tract, 

 but pass on in the brain-stem to the level of the inferior 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 dorsal spino-cerebellar 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 tliese from the lumbar region up to the level 

 of the second cervical nerve. 



In the ventro-mesial border of Gowers' tract and immediately upon the 

 periphery, near the antero-lateral sulcus (exit of ventral nerve-roots), there is 

 found in the higher segments of the cord a small oval bundle, the spino-olivary 

 fasciculus or Helweg's (Bechterew's) bundle. The functional direction of its 

 fibres has not been settled. 



It is asserted to arise from ceU-bodies of the ohve in the medulla oblongata, and in the cord 

 is believed to be associated with the ccUs of the ventral column of grey substance, probably 

 those of the lateral) horn. More recent claims assert that it arises fron cell bodies in the cord 

 and thus is spino-olivary. 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 connections, Ilelwcg's fasciculus is probably an indirect 

 cerebellar as.sociation with the spinal cord neurones. It is composed of axones of relatively very 

 small diameter, and it is one of the last fasciculi of the si)inal cord to become meduUated. 



Situated between the superficial ventro-lateral s]:)ino-cercbellar fasciculus and 

 the lateral fasciculus proprius is an area which, in transverse sections, may be, by 

 position, referred to collectively as the intermediate fasciculus. So intermingled 

 are the axones comprising it that it has been called the mixed lateral zone. It 

 contains fibres of at least five functional varieties: 



