THE SEXSORY PATHS 535 



ing."* Its cells possess similar connections and are similar in 

 function to those of Clarke's column. 



About the cells of these nuclei the third division of the dorsal 

 root fibres have their terminal arborizations. The central neurone 

 of this path, sensory neurone of the second order, begins with the 

 cells of Clarke's column, and to a much less extent from those of 

 Stilling's nucleus ; their neuraxes pass obliquely outward and up- 

 ward to reach a point near the surface of the lateral white col- 

 umns. Here they form a thin ribbon-like superficial zone which 

 spreads forward from the dorsal nerve roots to a point opposite the 

 central grey commissure. This superficial fibre bundle is the 

 dorso-lateral or direct cerebellar tract, so called because of its loca- 

 tion in the spinal cord and because of the distribution of its fibres, 

 which pass directly cephalad to the medulla oblongata, and thence 

 through the superficial zone of the restif orm body of the same side to 

 the vermis of the cerebellum. It is therefore, as are all other paths 

 from the spinal cord to the cerebellum, an uncrossed or direct tract. 



Those fibres of the direct cerebellar tract which enter at the 

 lower levels naturally assume the more superficial position. More- 

 over, since Clarke's column is not found as a distinct nucleus above 

 the thoracic region, the direct cerebellar tract does not appreciably 

 increase in size above this level. The neurones of this path proba- 

 bly transmit impulses which are chiefly derived from the abdominal 

 and thoracic viscera, hence it receives few fibres in the cervical 

 portion of the spinal cord. 



In the vermis cerebelli the terminal arborizations of fibres 

 coming from the direct cerebellar tract are undoubtedly in relation, 

 either directly or by collaterals, with the cerebellar cortex. How- 

 ever, the majority at least of its impulses leave the cerebellum 

 through the superior cerebellar peduncles by means of neurones of 

 the third order, decussate in the mesencephalon, and in great part 

 terminate in the red nucleus of the opposite side. 



It is thought, however, that some of the neurones of the supe- 

 rior cerebellar peduncles extend beyond the red nucleus without 

 interruption. These uninterrupted fibres are joined by the nerve 

 fibres of those sensory neurones of the fourth order, whose cell 

 bodies lie in the red nucleus, and together they continue the path 

 through " Forel's field," enter the posterior limb of the internal 

 capsule in relation with the fillet tract, and travel thence through 

 the corona radiata to the cortex cerebri. 



Cassel, 1859. 



