v ELECTROMOTIVE ACTION OF EPITHELIAL AND GLAND CELLS 467 



As regards the strength of the " rest current " under various 

 conditions, a very brief observation of the object in question makes 

 it plain that the electromotive reaction is far more dependent 

 upon external accidents and internal changes than is the case 

 with the muscle current. The individuality of the frog, its state 

 of nutrition, temperature relations, the time of year, and other 

 circumstances, affect the currents of the mucosa so strongly that 

 the results are extremely variable. 



On comparing the muscle current with that of the lingual 

 mucosa, the most striking point is the great inconstancy of the 

 latter, apparent in every kind of lead-off most of all, however, 

 by Hermann's method (supra) of leading off from the uninjured, 

 weakly curarised frog at the upper surface of the tongue, and 

 any indifferent portion of the body (from which the skin 

 has been removed, but which is otherwise totally uninjured), 

 such as the muscles of the thigh or leg. If, under these con- 

 ditions, the entering " current of rest " is at all vigorous, the 

 scale will hardly remain at rest for a moment after compensa- 

 tion, but swings in the direction of now increase, now decrease, 

 of the existing current. These oscillations, which are sometimes 

 merely indicated, may in other cases extend over many degrees 

 of the scale, while during the observation the current of rest 

 may take up a perfectly different mean. Sometimes the antagonistic 

 deflections occur with a tolerably regular rhythm, but in most 

 cases this is not recognisable. The possibility that the lingual 

 glands may, as has been shown, be innervated from the central 

 organ, suggests that the effects described may be due to a central 

 excitatory impulse ; the oscillations, however, also appear, though 

 as a rule feebly, in the preparations of the lower jaw described 

 above, so that in any case their immediate cause must be sought 

 in the tongue itself. 



If the lingual rest current is led off as above from the whole 

 uninjured frog, the lower jaw being drawn back as far as possible 

 by means of a thread passed through close to the tongue, while 

 the animal lies on its back, the current, immediately after applying 

 the electrodes, is almost invariably found to be rapidly increasing, 

 and it may happen that a current which is extremely weak when 

 the throat is first opened, will drive the scale out of the field a 

 few minutes later. On taking off and replacing the electrode in 

 contact with the surface of the tongue, at the same or any other 



