444 STUDIES IN GENERAL PHYSIOLOGY 
ing portion of the central nervous system shows the polar 
stimulation of the glands of the skin at the anode end when a 
current is passed through the piece in a longitudinal direction. 
Furthermore, an interesting difference was found between 
the head and the tail end of the animal in regard to the size of 
the secreting region. When an ascend- 
ed . . 
ing (homodromic) current was sent 
+ . __ through an isolated head, the secretion 
was limited to the outer edge at the 
; anodal side (cd, Fig. 130)—the cut end. 
poten If, on the other hand, a descending 
current was sent through the head, almost the entire head 
secreted (ab, Fig. 131). When an isolated tail was traversed 
by a descending current, the glands of only a small region in 
the neighborhood of the wound secreted (ab, Fig. 132). If an 
ascending (homodromic) current was 
sent through the tail, the glands in the 
whole region (cd, Fig. 133) secreted. It 
might be thought that the wound has an 
inhibiting effect upon the secretion of 
the glands lying in its neighborhood, 
and that for this reason the isolated head secretes most freely 
under the influence of a descending current, while an isolated 
tail secretes most freely under the influence of an ascending 
current. It can easily be shown, however, that the wound 
does not play this 
| + role, but that in 
general those por- 
tions of the animal 
lying near the head secrete more freely and over a larger 
region when a descending current is used than when an 
ascending current is used, while the posterior pieces secrete 
most strongly under the influence of an ascending current. 
For when the head of an animal is amputated, and the pos- 
a 0 
FIG, 131 
FIG, 132 a b 
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