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. 



