ELECTROMOTIVE PHENOMENA IN GLANDS. 519 



with one and the same stimulus, applied at intervals during 

 the removal of water, to start with an outgoing "action 

 current," and passing through diphasic variations with a 

 predominant phase in either direction, to finally arrive at a 

 stage with purely ingoing "action current," when the "rest 

 current" is reduced to the utmost. In cases of artificial 

 reversal of the "current of rest," so that it becomes out- 

 going, the "current of action" becomes ingoing. 



These experiments, especially those with the non-muscular 

 tongue glands of the frog, overthrow the hypothesis of Her- 

 mann above mentioned, not only by the demonstration that 

 contractility is not a necessary factor in the phenomena, 

 but by indicating in the phenomenon of "reversal" that 

 the rather crude hypothesis, that the "current of rest" 

 owes its source to a keratinised or mucous demarcation 

 surface, is not tenable. Indeed, previously published ex- 

 periments with the secreting skin of the eel had already 

 demonstrated the difficulty of Hermann's position. 



The effect of Bach and Oehler in converting an outgoing 

 into an ingoing "action current" in the frog's skin, by pen- 

 cilling with corrosive sublimate, is explained by Biedermann 

 as being due to the reduction of the " current of rest " pro- 

 duced, and the dependence of the direction of the "action 

 current" upon the magnitude of the "rest current ". 



Bohlen, in his experiments with the gastric mucosae, 

 corroborates the main points of Biedermann's theory. In 

 the case of the frog, he considers that the ingoing " current 

 of rest " of Rosenthal is in the main, if not entirely, the 

 result of the activity of the superficial mucous cells, and is 

 not contributed to, to any large extent, by the gastric glands. 

 Ordinary digestive activity (feeding with meat) does not 

 markedly affect the current of rest, while the introduction 

 into the stomach of substances tending to produce excessive 

 secretion of mucus, such as small sharp pebbles, hard 

 scaled insects, or the minute angular crystals of subnitrate 

 of bismuth, causes a great increase in the electromotive 

 force of the "current of rest" of the stomach. Vagus 

 excitation in the frog produces an ingoing "action current," 

 and this he thinks is possibly of gastric gland origin, since 



