Secondary Degeneration following Unilateral T.esions etc. 319 



through the lower half of the decussation; above that level they con- 

 sist of isolated fibres. 



In the spinal cord sections through the P*^ cei'vical segment show 

 the degenerated crossed pyramidal tract occupying a rounded area in 

 the posterior part of the right lateral column, in close contact with 

 the lateral border of the posterior horn and well I'emoved from the 

 periphery of the section. One or two detached bundles are seen 

 within the grey matter at the base of the posterior horn. There is a 

 considerable number of degenerated fibres scattered throughout an 

 area on the left side corresponding to that of the crossed pyramidal 

 ti-act on the right. Neither at this nor at any other level of the 

 spinal cord is there any trace of a direct (anterior) pyramidal tract. 

 In sections through the 6^^^ cervical segment the right crossed pyra- 

 midal tract occupies a comparatively small rounded area in the poster- 

 ior part of the lateral column, but it does not reach the posterior 

 horn and there is a considerable space between it and the margin of 

 the section free from degeneration. About a dozen degenerated fibres 

 can be counted in the crossed pyramidal tract on the left side. In 

 the mid-dorsal region and at the level of the 3^'^^ lumbar segment the 

 crossed and direct lateral pyramidal tracts are visible, the number of 

 fibres in each gradually diminishing. In all the regions of the cord 

 examined the crossed pyramidal tract occupies a comparativelj^ small 

 area but this may possibly be due to the lesion not having involved 

 all the cortico-spinal fibres. In the lumbar region some fine degene- 

 ration is present at the base of the posterior horn on the right side. 



Monkey. Case I. Macacus Rhcesus. Male. Lesion. This was 

 produced as already described, and was found to involve the whole 

 left Eolandic area. The animal was killed 31 days after the operation. 



Synixjtoms during Life. There was loss of voluntary power in 

 both right limbs; the grasping power was feeble and there was 

 marked right sided weakness in walking and climbing. The lameness 

 gradually disappeared after the first few days, but true voluntary 

 power did not return. Tactile sensibility was present from the first in 

 the right arm, but absent in the right leg, and a pin prick appeared 

 to cause pain in both right limbs. Until the 12^^ day after the oper- 



