THE SPINAL CORD 



673 



tion. This has been worked out largely from careful clinical observa 

 tions made upon patients who are suffering from definite cord lesions, 

 the nature of the lesion in each case being determined subsequently 

 by post-mortem examination. The impulses connected with pain 

 oross at once to the opposite side, and ascend in the spino-thalamic 

 tract. Thermal impulses do not cross quite so soon, but take a very 

 similar course. Tactile impulses pass up on the same side for 

 four or five segments of the cord, and then cross, to ascend in the 

 anterior region of the cord. Kinaesthetic impulses, concerned with 



Homolater.il impulses uiiderlving muscular sensibility (passive position 

 and of movement), also of touch and pressure for a few segments 



Hetero-liUci al 

 unconscious 

 afferent im- 

 pulses under- 

 lying muscular 

 co-ordination 

 and reflex tone 



All itupul.se:) of 

 pain, of hunt 

 ,' and cold 



'hetero-latjral) 



Impulses of touch and pressure (hetero-lateral) 

 Fip. 398. 



1, Fibres in posterior column; 2, fibres in Clarke's column; 3, fibres to cells uf pos- 

 terior horn; 4, fibres to cells of anterior horn; 5, fibres to cells of lateral column; 

 6, dorsal cerebellar tract; 7, ventral cerebellar tract; 8, spino-thalamic and tectal 

 tracts; 9, ascending fibres in anterior columns. (W. Page May, by permission 

 of the editor of Brain.) 



the sense of passive position and movement, pass up in the postero- 

 median and postero-lateral columns of the same side. Impulses con- 

 cerned in co-ordination and reflex muscular tone which do not enter 

 into consciousness, pass up on the same side in the dorsal spino- 

 cerebellar, and on the opposite side in the ventral spino-cerebellar 

 tract (Fig. 398). 



The Effect of Transverse Section. The effect of transverse section 

 depends according as it is partial or complete. Section of one half 

 (hemi-section) leads to a loss of movement on the same side as the 

 lesion in the parts supplied by nerves ar sing below the site of injury. 

 It also leads to a partial loss of sensation in the same area. The kime >- 



43 



