THE SPINAL CORD AS A CONDUCTOR 491 



the outer and hinder part of the lateral columns (Fig. 

 155, Ch., CO.). The degeneration which marks its course 

 results solely from sections of the cord itself, and not of 

 any of the spinal nerve roots. It begins in tlie lower end 

 of the cord at the level of the second lumbar nerve, 

 passes straight up to the spinal bulb and then into the 

 cerebellum by means of the inferior peduncle (see p. 506) 



p m. . 



. P'^- 



asc.a.i.-' 



asc. a.L. 



AF 



Fig. 155. — Diagram to show the Position of Tracts o? Ascwtdino 

 Degeseratios is thk White Matter of the Spisal Cord at the 

 Level of the Fifth Cer%-ical Nerve. 



A.V, anterior fissure; P.F. posterior fissure; p.m., p7. the median 

 and lateral posterior tracts, or traut of fibres from the posterior roots of 

 the spinal nerves; Ch, Cb, the cerebellar tract; ate. a.l., asc. a.l. the 

 ascending antero-lateral tract. 



The grey matter of the cord is shaded black. 



ot«this part of the brain. The fibres in this tract originate 

 from processes of those cells in the grej' matter which 

 form a conspicuous group at the base of the dorsal horn, 

 and are known as Clarke's column. These cells are 

 seen most conspicuously in the thoracic, the upper cervical 

 and the sacral regions of the cord. Those from the sacral 

 region do not contribute to the Direct Cerebellar Tract. 

 (See Fig. 150, 3). 



(lii). The Ascendine: Antero-lateral Tract. — This tract, 

 like the cerebellar, can only he made evident as the 

 result of injury to the cord itself. Its fibres originate in 

 the cells of Clarke's column in the lower portion of the 

 spinal cord. It lies in the outer and anterior part of the 



