Secondary Degeneration following Unilateral Lesions etc. 323 



tlie transverse section of the tract filled entirely witli degenerated 

 fibres, bnt there was always a varying proportion of normal fibres 

 intermingled with those degenerated. 



Summary of Results and Comparison with those of former 



Investigators. 



1. Physiological. A complete severance of the projection fibres 

 arising from the motor cortex of one cerebral hemisphere, with as little 

 injnry to adjacent parts as was practically possible, was found to be 

 followed by motor paralysis of the opposite side of the body. This 

 was recovered from almost completely in the cats, and to a large ex- 

 tent in the monkeys, so far as "associated movements" were concerned 

 (walking, climbing), but the power to perform purely voluntary 

 movements did not, as a rule, return during the time the animals 

 were under observation. In the case of the cat, however, if the stim- 

 ulus was very powerful, apparently voluntary movements were often 

 executed with the paralysed limb; e. g. if the cat was prevented from 

 getting at food with its left fore-paw it would use its right,, although 

 under ordinary circumstances it preferred to use the left. In the 

 cats "associated movements" were recovered much earlier than in the 

 monkeys. 



Regarding the effects of the lesion on sensation there was not 

 the same constancy. Frequently there was deficient or abolished tac- 

 tile sensibility on the paralysed side, but in many cases this was not 

 so, and in one or two cases there seemed to be hyperaesthesia. As 

 a rule, sensation when absent or deficient was very quickly restored. 

 In no case was heat sensibility absent although almost always de- 

 layed. In four cases there was hemianopsia. As a rule the temper- 

 ature of the paralysed limbs was lower than that of the opposite 

 side, but in one case it was higher. These differences in temperature 

 between the two sides of the body soon vanished, indicating that the 

 vasomotor disturbances which had probably caused it had passed off. 

 The knee-jerk was almost always brisker on the paralysed than on 

 the non-paralysed side. 



The cases described emphasise the fact that there is no direct 



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