THE CENTRAL NERVOUS SYSTEM. 



95 



oblongata. Most of these fibres cross in the pyramidal decussation 

 to form the crossed pyramidal tract, and terminate by turning into 

 the grey matter of the spinal cord, where they pass their impulses on, 

 probably through an intermediate neuron, to the cells of the anterior 

 horn, the axons of which become the motor fibres of the nerves to the 



d 



FIG. 28. Diagram showing paths of 

 sensory impulses. 



a, Skin ; b, muscle ; c, funfculus gracilis ; d, 

 spino-thalamic tract ; e, nucleus gracilis ; 

 /, thalamus. 



FIG. 29. Diagram showing the paths 

 for motor impulses. 



Cell in anterior horn of grey matter ; b, cell in 



K.eiior horn ; c, crossed pyramidal tract ; 

 irect pyramidal tract ; e, decussation of 

 pyramids ; /, motor area in cortex. 



skeletal muscles (fig. 29). The pyramidal fibres which do not cross in 

 the medulla oblongata form the direct pyramidal tract of the spinal 

 cord, and cross by degrees to the grey matter of the opposite side to 

 come into relation with the cells of the anterior horn. Some of the 

 uncrossed fibres join the crossed pyramidal tract of the same side, and 

 their further course is unknown. Generally speaking, however, the 



