508 ELECTRO-PHYSIOLOGY CHAP. 



Many of these manifestations, in particular the frequent alter- 

 nation in direction of the deflections, which appears spontaneously 

 without any demonstrable cause, sometimes also rhythmically, 

 seem to indicate that each cell is to be regarded as the seat of tivo 

 distinct chemical processes, which existing simultaneously -produce 

 heterodromous potentials. The observed deflection would therefore 

 always ~be the sum of two antagonistic forces. 



In order to explain the rapid diminution and final reversal 

 of the normal ingoing current of the skin and mucosa after cool- 

 ing, we must assume that one of the two current-generating 

 processes (that indeed which implies the development of nega- 

 tive potential) is injured earlier, and to a greater degree, by 

 cold, than the other, so that an outgoing current results from the 

 preponderance of the latter, which in turn gives way to an in- 

 going current so soon as the normal conditions are restored by 

 heating. The " negative process " appears to be less resistant to 

 other effects also than the " positive." Thus, as we have seen, 

 the suitable abstraction of water will also revive the entering 

 current ; on the other hand, lack of oxygen, or treatment with 

 C0 2 , or anaesthetising substances (alcohol, ether, chloroform) 

 impair to the same extent, and eventually abolish, both current- 

 generating processes. In this respect again the perfectly different 

 behaviour of nerve and muscle currents should be noted, in 

 which under these last conditions the diminution is relatively 

 late in appearing. 



It is not possible at this juncture to say anything as to the 

 precise nature of these chemical processes in the secretory cells, 

 although one is tempted to conjecture the secretion of water on 

 the one hand, and organic specific secretory constituents on the 

 other. And in favour of this view it might be added, that the 

 entering cloacal current is always strongest when the mucosa is 

 most richly covered with watery secretion, and that while the 

 negative potential of the surface generally increases with the 

 bulk of water present, it rapidly diminishes with loss of water. 



This same interpretation also found unlooked-for support in 

 the experiments described above on the mammalian stomach. 



The extraordinary influence of changes in blood-pressure on 

 the magnitude of E.M.F. in the abdominal mucosa are at any 

 rate to be referred to this explanation. There can be no doubt 

 that the secretion of water by glandular organs, apart from other 



