206 SECONDARY ELECTROMOTIVE PHENOMENA IN 



Hoots reversed. 

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Roots reversed. 

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+ 17 



In order to judge of these figures correctly it must be remembered 

 that the currents were still led off to the nerve multiplier through 

 platinum in saline solution, in the old way. After a momentary 

 current the returning needle would swing back over the zero point 

 into the other quadrant, and here it would be perhaps carried 

 beyond its deflection in the first quadrant in consequence of the 

 charging of the platinum plates. The polarisation- current of nerves 

 is not however comparable to an instantaneous current of this kind. 

 Even the negative polarisation, although the more transitory of 

 the two, sinks more or less gradually. The middle point of oscilla- 

 tion for the undamped needle is therefore temporarily transferred 

 to the negative quadrant, as we will call it. In its backward swing 

 the needle may indeed cross the zero point, but its positive deflection 

 will not exceed its negative. If this should happen, we may conclude 

 that action successively in opposite directions is present. Con- 

 sequently where in the above table a larger positive number follows 

 a smaller negative one, action in two directions occurred, that is to 

 say, a negative after-current changed suddenly into a positive one, 

 and the difference of the numbers gives an approximate measure for 

 the comparative strength of the latter. Accordingly in both tables 

 up to the mark || we have the expected result. The subsequent ap- 

 pearance of the opposite result reminds us of the reversal of the normal 

 relation in the two halves of a regular muscle (Sect. 10). Almost 

 without exception the series began normally in the roots, but fre- 

 quently the reversal took place not later than the second or third 

 momentary current. This was especially the case in the motor roots, as 

 in the examples given the sensory roots exhibited the condition in 

 question longer than the motor ones. If we consider that in these 

 experiments both sides of the separated roots were brought into 

 contact with white of egg and injured with electric shocks, one can- 

 not avoid the impression that apparently, in spite of all imperfec- 

 tions, they render the thesis probable that, In motor roots positive 

 polarisation predominates in a descending direction, and in sensory 

 roots in an ascending direction ; the direction in both cases being that 

 of the physiological innervation wave. Certainly until more is known, 



