v ELECTROMOTIVE ACTION OF EPITHELIAL AND GLAND CELLS 509 



influences, does depend essentially on the actual pressure, and it is 

 at first sight surprising that in the frog neither vagus excitation, 

 nor complete abolition of circulation, produces any such effect on 

 the electromotive properties of the stomach as is proved to be 

 the case in mammals, when a relatively low fall of pressure in 

 the abdominal vessels produces a marked negative variation of 

 the ingoing current. Yet this is intelligible in view of the extra- 

 ordinary resistance of the frog's skin to all injuries whatsoever. 

 Accordingly, if decrease of pressure in the vessels of the abdominal 

 mucosa is unfavourable to the secretion of water, a negative varia- 

 tion must follow, if as we are justified in supposing the actual 

 difference of potential is the sum of two antagonistic electro- 

 motive processes, one of which gets the upper hand, as soon as 

 any current manifests itself. And this appears, inter alia, from 

 the circumstance that the death of the animal from any cause 

 whatever, is followed under normal conditions by a rapid decline 

 and subsequent reversal of the current. So that the decrease of 

 blood -pressure in warm-blooded animals seems to work like 

 marked cooling upon the mucous glands of the cold-blooded, in- 

 asmuch as if the expression is legitimate the negative in both 

 cases declines more quickly than the opposite positive process. 

 From this point of view it is easy to explain, not merely the 

 coincidence of result in vagus excitation, marked loss of blood, 

 and diminished blood-pressure due to any poison (amyl nitrite, 

 pilocarpin, chloral, curare, etc.), but also the later effects of dysp- 

 noeic, or ansemic, excitation of the cerebral vaso-motor centres. 



Further confirmation of the view thus laid down re the 

 effective cause of the normal, ingoing, abdominal current, appears 

 from the results of infusion of salt solution. Here the occasionally 

 enormous secretion of water by the mucosa of the stomach 

 may be directly observed, and when as frequently happens 

 there is, notwithstanding the pronounced dilution of the 

 blood and consequent malnutrition of the tissues, a marked 

 increase of electromotive action in the mucosa in the sense 

 of the normal ingoing current, the only explanation possible in 

 the last resort is that the observed differences of potential, and 

 increased secretion of water, are in causative relation. 



Bayliss and Bradford (87) previously came to the same con- 

 clusions with regard to dependence of electromotive action in the 

 salivary glands on the nature of the secretion. 



