148 



LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



spinal ganglion all its fibres degenerate. The ganglion itself 

 and the root originating in it remain normal. This shows that 

 the cut has severed all the fibres from their cells. If we cut the 

 posterior root just back of the ganglion, only a few fibres of the 

 sensory nerve become degenerated and the majority remain 

 intact. The nerve must, therefore, consist of fibres which 

 originate in the spinal ganglion-cells, for the connection be- 

 tween these is unbroken. The fibres which were destroyed 

 must have come from the spinal cord itself, for they are only 

 severed from the latter and not at all * 



FIG. 87. 



Diagram of the relations of the nerve-roots 



to the spinal cord. 



Gemischtcr N?>-v., Mixed nerve. Hint. Wurzel, Post. root. 



Mot. Theil, Motor part. Sens. Theil, Sensory part. 



Vordere Wurzel, Ant. root. 



FIG. 88. 



Diagram of the fibres of a spinal 

 ganglion. 



Hint. Wurzel, Post. root. 



from the ganglion. 



An examination of the root after this latter 

 experiment will account for this. The root is divided from the 

 ganglion, and we find that only a few fibres have remained 

 sound: the majority have been destroyed. The fibres which 

 remain uninjured must have their source in the spinal cord, for 

 they are connected to it alone; the fibres which perish must 

 come from the spinal ganglion, for their connection with it alone 

 was severed. 



Experiments show that cell-processes pass out of the gan- 



