MTJSCITLAR COORDINATION. 289 



The anatomical relations of the posterior white columns, 

 the results of experiments upon living animals, and certain 

 well-marked pathological phenomena, point very strongly to 

 a connection between these columns and the coordination 

 of muscular movements. 



Probable Function of the Cord in Connection with Mus- 

 cular Coordination. Anatomists have not been able to trace 

 satisfactorily the direction of all of the fibres contained in the 

 posterior columns ; but it is probable that at least some of 

 these fibres serve as longitudinal commissures, and connect 

 together the nerve-cells, extending for a greater or less dis- 

 tance both upward and downward in the cord. This ana- 

 tomical arrangement is rendered probable chiefly by the re- 

 sults of experiments. 



If the posterior columns be completely divided, by two or 

 three sections made at intervals of from three-fourths of an 

 inch to an inch and a quarter, the most prominent effect is 

 a remarkable trouble in locomotion, consisting in a want of 

 proper coordination of movements. These important ex- 

 perimental results were obtained by Yulpian. 1 



In the remarkable disease known under the name of 

 locomotor ataxia, 2 there is a very peculiar condition of the 

 muscular system, in which, while the power of the muscles 

 is but slightly diminished, the movements of progression 

 show great deficiency in coordinating power, frequently at- 

 tended with more or less disturbance in the sensibility of the 

 parts affected. These symptoms are associated with struc- 

 tural disease of the cord, limited to the posterior columns 

 and the posterior roots of the spinal nerves. 



Many years ago, before locomotor ataxia had been gener- 

 ally recognized by pathologists, Todd made the following re- 

 markable statement with regard to the posterior columns : 



1 YULPIAX, Systeme nerveux, Paris, 1866, p. 381. 



8 For a description of this disease, see, HAMMOND, Diseases of the Nervous 

 System, New York, 1871, p. 484, et seq. 



