STRUCTURAL ALTERATIONS IN NERVE CELLS 
221 
Side opposite Lesion. 
Segment 
Post lat. Ant. lat. 
Central 
3 
5 
VL 
VIL 
VIII. 
IX. 
13 i 
No altered cells found. 
2 
2 
2 
8 
Summary of Section V 
In Experiment i the results obtained are about the same as those previously recorded by 
me after section of the afferent roots alone ; that is destruction of the cortical afferent fibres does 
not appear to have influenced the cells to an appreciable degree, but in Experiment 2 the effect of 
the double lesion is pronounced. In that case more roots were cut and included those, viz. Vlltli 
and Vlllth, w^hose integrity appears to be especially necessary for the maintenance of the 
functional activity of the cells of the anterior horns. The condition observed in this experiment 
differs also in another particular from that which is found after section of afferent roots alone, 
namely, the marked extent to which the side opposite to the lesion is affected. 
I am not able to offer any satisfactory explanation of tliis fact. In the experiments quoted 
in rny former paper {he. cit.) it was found that after section of the posterior roots the Vlth segment 
on the side of the lesion was found to be free from any altered cells, whereas the opposite side 
contained a few. The absence of changes in this segment is significant, for its motor fibres supply 
the extensor muscles and extension is very rarely produced as a primary reflex movement. On 
the other hand the observations made on the course of degenerated fibres give no support to the 
view that the fibres of the posterior roots cross in the spinal cord. The peculiar distribution 
cannot, I think, be regarded as accidental or due to vascular disturbance resulting from the 
operation, but must in some way be connected with the physiological interference. 
