On THE THEORY OF GALVANOTROPISM 441 
rent is kept up; finally a tiny mucous plug is noticed in each 
of the glands. 
If the current is sent through the animal in an ascending 
direction, a profuse secretion occurs upon the tail (Fig. 
127, cd). The amount of the secretion formed is, with the 
FIG. 126 
same density of current, much greater than that formed 
upon the head, and within a short time a thick white layer 
is formed which drops off readily when the animal moves. 
The secretion may be profuse enough to render the water in 
the trough turbid in a short time. 
FIG. 127 
If the current is passed in a transverse direction through 
the animal, secretion occurs only upon one-half of the body 
—upon the half directed toward the anode. 
We see, therefore, that in all three cases the glands of the 
skin upon the anodal side or the anodal end of the animal 
are always the ones to begin to secrete. The results are the 
same whether metallic electrodes or unpolarizable electrodes 
are used. 
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