On THE THEORY OF GALVANOTROPISM 445 
terior portion is cut off at a short distance behind the 
snterior 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 
region ab (Fig. 131), 
+ ee NRTAR Oy 
d@d 
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 FIG. 134 
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 ab when a descend- 
ing current was sent through the animal. We then de- 
stroyed the anterior part of the spinal cord (Fig. 136) from 
the point S to S, by means of a needle. When a current 
was again sent through the piece in a descending direction, 
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