ON THE THEORY OF GALVANOTROPISM 



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terior portion is cut off at a short distance behind the 

 anterior legs, the remaining piece (Fig. 134) has a wounded 

 surface at each end. The fragment, however, belongs to the 

 anterior end of the animal, and therefore behaves like the 

 head ; that is to say, under the influence of a descending cur- 

 rent the secretion 

 Covers the extensive 



c region o7> (Fig. 131), 



FIG. 133 while under the influ- 



ence of an ascending current secretion is limited to the nar- 

 row zone cd (Fig. 135). When the corresponding experi- 

 ment is made upon a piece cut from 

 the posterior half of the animal, a 

 more extensive secretion is obtained 

 when an ascending current is used ~ 

 than when a descending current is 

 employed. 



4. What becomes of the galvanic 

 secretion when the spinal cord is destroyed ? Pieces cut from 

 the trunk in which I had destroyed the spinal cord showed 

 no polar excitation of the glands of the skin when the cur- 

 rent was passed in a, longitudinal 

 direction. The effect on the central 

 nervous system is shown in a still 

 more striking way when the latter is 

 destroyed only in part. We experi- 

 mented upon a piece, as shown in 

 Fig. 134. We convinced ourselves 

 first of all of the fact that secretion 

 occurred anteriorly in about the region ah when a descend- 

 ing current was sent through the animal. We then de- 

 stroyed the anterior part of the spinal cord (Fig. 13(5) from 

 the point S to S' 1 by means of a needle. When a current 

 was again sent through the piece in a descending direction, 



FIG. 134 



FIG. 135 



