THE SPINAL CORD AND CEREBELLUM 113 



supposed to be present in the sacral region and in the 

 medulla oblongata.* The region of its greatest 

 development is the lower dorsal and upper lumbar. 

 The axons or main fibres of these cells are coarse, and 

 pass, as stated, to the inferior peduncle of the cere- 

 bellum forming the cerebellar tract. 



In attempting to determine the functions of the 

 various parts of the white and gray matter of the cord, 

 it is necessary to consider, firstly, their anatomical 

 relations so far as these happen to be known ; 

 secondly, the size of the cells and fibres ; thirdly, the 

 nature of the impulses, chemical, sensory, or other- 

 wise, which may constitute a part of their environment ; 

 and, fourthly, the character of the degeneration they 

 undergo after section or in pathological cases. 



By a very general consensus of opinion the direct Pnnotion 

 and crossed pyramidal tracts have been set aside as pyramidal 



■^•' tracts. 



the chief, if not sole, paths of motor impulses to the 

 skeletal muscles. They both end by forming arbor- 

 escences round the large cells of the anterior horn.t 

 The fibres of the direct tract! are said to cross by the 

 anterior commissure, but this has been denied. § The 

 united pyramidal tract as it passes down through the 

 lower parts of the brain from the cortex of the 



* Foster, loo. cit., p. 957. 



f Recent research, I have been informed, has revealed a con- 

 nection between the pyramidal tracts and the cells of Clarke's 

 column. 



I Foster, loo. cit., p. 962. 



§ Bechterew, loc. cit., p. 94 : ' Der vordere Pyramidenstrang 

 hat demnach Beziehungen zu Nervenzellen des gleichseitigen, 

 nicht aber zu solchen des entgegengesetzen Vorderhornes.' 



8 



