ON THE MAMMALIAN NERVOUS SYSTEM. 437 



posterior columns. That it affects the cord on the side of the lesion is probable from 

 the results just given, but the direct proof is wanting since the increased intensity of 

 the effect is masked by the large diminution caused by the severance of the direct 

 tract in the posterior column of the same side. There is, however, no such sever- 

 ance in the case of the opposite side, and the increased excitability is plainly seen* 

 as evidenced by the cases marked with an asterisk, in which the section was followed 

 by actual increase in the cord effect. Whatever may be the meaning of this it 

 undoubtedly is a most important factor to be taken into consideration in all experi- 

 ments the general plan of which consists in first causing definite lesions, and then 

 examining the influence of such. It will be obvious too, that in proportion as the 

 anaesthetic is removed so much the more marked must this change in excitability 

 become. In the experiment upon conduction already referred to, made by MIESCHEB, 

 in which the reflex effect on the blood pressure was taken as the index of the passage 

 of afferent impulses through a block in the cord, any change of this kind could not 

 be allowed for as owing to the curarisation of the animal, the observation of con- 

 comitant reflex movements was impossible. We venture to think that the increased 

 effect obtained by MIESCHER on the side of the complete section in his division 

 of every part of the cord except one lateral column, and taken by him. to mean 

 that the afferent fibres crossed into the lateral of the opposite side, was due to some 

 such increased excitability in the lower fragment of cord on the side of the main 

 lesion, the fibres of the lateral tract connecting this fragment with that above as 

 internuncial fibres. 



It is obviously impossible to put this factor completely out of court. The cord 

 effect with which we are dealing is a measure at once of the intensity and the number 

 of all transmitted excitatory processes, and the influence of any particular section can 

 therefore only be judged of by taking the average of all the readings, high and low. 

 It might be thought that by pushing the anaesthesia and by decreasing the strength 

 of the stimulus the effect would always become uncomplicated. Although anaesthesia 

 lessens the chance of its occurrence it would appear that this increase in the cord 

 effect will sometimes occur even under these conditions; and it is then evidently 

 dependent upon the character of the particular preparation used. Its presence or 

 absence in these cases may, however, be not merely due to the idiosyncracy of the 

 animal, but to minute differences in the extent of the lesion in certain instances. 



The general result of experiments on four Cats and two Monkeys is as follows : 



