D. C 



GREY AND WHITE MATTER IN THE SPINAL CORD 839 



(3) A tract of scattered degeneration lying along the margin of the 

 cord in the anterior portion of the antero-lateral column, and partly 

 overlapping the tract of Gowers. It is called the antero-lateral 

 descending tract, or tract of Loewenthal, or the vestibulo-spinal tract. 



(4) The prepyramidal (or rubro- spinal) tract, or Monakow's tract 

 (also called the fasciculus intermedio-lateralis) , lying immediately in 

 front of the crossed pyramidal tract. 



(5) A small, comma-shaped island of degeneration (comma tract] 

 can be followed downwards for a short distance in the middle of 

 Burdach's column. It is only 



seen in the cervical and 

 upper thoracic regions. 



Less well known descending 

 tracts are 



(6) The olivo - spinal and 

 thalamico - spinal tracts (or 

 Helweg's bundle) in the anterc- 

 lateral column opposite the 

 head of the anterior horn. 

 This tract does not pass down 

 beyond the lower cervical re- 

 gion. The olivo-spinal tract 

 appears to consist of fibres 

 running down from the olivary 

 body into the cord, while the 



thalamico-spinal tract is made Fi - ^34^-SchjBM of^Cross-Section^ of ^Spinal 

 up of descending fibres origina- 

 ting in the optic thalamus. 

 This is an important tract in 

 the lower vertebrates, but not 

 in man. 



(7) The tract of Marie in the 

 anterior column is chiefly a 

 continuation into the cord of 



the posterior longitudinal bundle, one of the conspicuous tracts of the 

 brain-stem or upper portion of the cerebro-spinal axis (p. 857). It 

 contains both ascending and descending fibres. 



When we have deducted the long ascending and descending tracts 

 which have been described, there still remains in the antero-lateral 

 column a balance of white matter unaccounted for. This white 

 substance, which does not degenerate for any great distance either 

 above or below a lesion, is called the antero-lateral ground-bundle, 

 and lies chiefly in the form of an incomplete ring around the grey 

 matter. For descriptive purposes it is sometimes distinguished as 

 the anterior ground-bundle (or fasciculus anterior proprius) in the 

 anterior column, and the lateral ground-bundle (or fasciculus lateralis 

 proprius) in the lateral column. It is believed to consist of fibres 

 (endogenous or proprio-spinal fibres) which run only a comparatively 

 short course in the cord, and serve to connect nerve-cells at different 

 levels. Some of these endogenous fibres are ascending, others 



D.P 



Cord (Donaldson, after Lenhossek). On the 

 left side only the afferent fibres are shown; 

 the efferent fibres and the spinal cells on the 

 right side. D.R., posterior (dorsal) root; 

 V.R., anterior (ventral) root; C.P., crossed 

 pyramidal fibres; C., direct cerebellar tract; 

 A.L., antero-lateral tract; D.C., posterior 

 columns. 



