444 



STUDIES IN GENERAL PHYSIOLOGY 



FIG. 130 



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- 

 ing (homodromic) current was sent 

 through an isolated head, the secretion 

 was limited to the outer edge at the 

 anodal side (c(/, Fig. 130) the cut end. 

 If, on the other hand, a descending 

 current was sent through the head, almost the entire head 

 secreted (cf&, 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- 



FIG. 132 



a 



