472 



COMPAEATIVB PHYSIOLOGY. 



the posterior columns of the cord. The essential feature is an 

 inability to co-ordinate movements, though muscular power 

 may be unimpaired. But such inco-ordination is not usually 

 the only symptom; and, while the disease seems usually to 

 begin in Burdach's columns, the columns of GoU, the posterior 

 nerve-roots, and even the cells of the posterior comua, may be 

 involved, so that the subject becomes very complicated. Co- 

 ordination of muscular movements is normally dependent upon 

 certain afferent sensory impulses, themselves very complex. It 

 is to be remembered also that there are numberless connecting 

 links between the two sides of the cord and between its different 

 columns of an anatomical kind, not to mention the possibly 

 numerous physiological (functional) ones. 



Pia. 336.— Diagram to illnstrate probable course taken by fibers of nerve-roots on en- 

 , . tering spinal cord (Schafer). 



'I "\ 



; r. . -^e have stated above that section of one lateral half of the 

 'co'ridis followed by loss of sensation on the opposite side of the 

 ■ "body"; but directly the contrary has been maintained by other 

 ■observers; while still others contend that the effects are not 

 confined to one side, though most pronounced on the side of 

 •the section. The same remark applies to motion. 



While there is considerable agreement as to the pyramidal 

 tracts of the lateral column, the functions of the rest of these 



