442 STUDIES IN GENERAL PHYSIOLOGY 



That we are, indeed, dealing with the effects of a con- 

 stant current is shown by the fact, first of all, that the longer 

 the circuit is closed, the longer does secretion last, the 

 greater is the amount of the secretion, and the greater 

 the region in which the secretion occurs; secondly, that the 

 secretory phenomena are brought about when the intensity 

 of the current is raised very slowly. The breaking of the 

 current, on the other hand, has no effect. 



2. The next question that presented itself was whether 

 we dealt in this case with the effects of the current upon the 

 skin or the glands themselves, or whether we had to do with 

 a stimulation of the central nervous system. We next in- 

 vestigated the action of the current upon animals in which 

 the spinal cord had been cut. When a current was passed 

 longitudinally through such animals, they behaved as though 

 they consisted of two fully independent pieces. If we call 

 that portion of the animal lying anterior to the cut the 

 anterior animal, and that lying behind it the posterior 

 animal, then the end of both the anterior animal and the 

 posterior animal which was directed toward the anode secreted 

 during the passage of a current longitudinally through the 

 animal. In Figs. 128 and 129 S marks the position at which 

 the spinal cord was severed. In a descending current not 

 only the piece ab (Fig. 128) at the head end of the animal 

 secretes mucus, as in the case of the normal animal, but 

 also the anterior region cd of the posterior part of the 

 animal, which under otherwise similar conditions never 

 secretes in the uninjured animal. When the current passes 

 in an ascending direction, secretion occurs not only at the 

 tail (cd, Fig. 129), as in the uninjured animal, but secretion 

 occurs also at the posterior end of the anterior part of the 

 animal (ab, Fig. 129). The secretion in the latter case often 

 limits itself to the hindmost edge of the immediate vicinity 

 of the wound, and does not extend forward until the current 

 has passed through the animal for some time: 



