502 ELECTRO-PHYSIOLOGY CHAP. 



stomach, the other being in contact with the external surface of 

 the stomach. This in rabbits and guinea-pigs is nearly always 

 crammed with food, so that the lead-off from the mucosa is here 

 complicated by the contents of the stomach, which suggests cer- 

 tain objections. In the first place, one asks whether warmth 

 may not have a perceptible effect on the electrode inserted deep 

 into the stomach ; in the second, differences of potential are 

 caused by the contents of the stomach, so that the results of the 

 observation are disturbed to an extent which it is impossible to 

 calculate. 



In regard to the first question, it is easy to see that the 

 currents caused by differences of temperature do not come into 

 the reckoning at all, in comparison with the marked effects of the 

 physiological mucosa current. The second question is solved by 

 the fact that almost directly after the death of the animal there 

 is a decline of E.M.F. which soon tends to reversal of the 

 current, but this current appears in the same way and at the 

 same intensity whether the stomach is emptied and washed, and 

 then led off directly from the surface of the mucosa, or whether 

 it is already empty, e.g. in rats that have been kept without food 

 for some days. 



In warm-blooded animals, as in the frog, the intensity of the 

 rest current varies in individual cases, within a certain range. 

 Sometimes, nearly always indeed, it is so strong that the scale 

 flies far off the field ; in other cases again only deflections of a 

 few degrees are visible. Oscillations occur almost invariably, 

 which are of very different magnitudes. 



The effect of deep narcosis upon the strength of the current 

 in the mucosa of the stomach is very striking in mammals. 

 With a little care in the use of chloroform and ether, the 

 variation can be diminished until the deflection barely reaches 

 10 degrees of the scale. A long period must then elapse before 

 the current returns to its original magnitude. Whether this 

 is a direct or indirect effect is foreign to our present discussion. 



As in the frog, so in warm-blooded animals, the E.M.F. of 

 the mucosa is considerably heightened by the introduction of 

 bismuth (2-5 grs. in emulsion), along with which there is 

 an easily-confirmed increase in the mucin secretion. 



Artificial excitation of the vagus nerve produces striking 

 consequences. While the only result in the frog is a weak, positive 



