v ELECTROMOTIVE ACTION OF EPITHELIAL AND GLAND CELLS 469 



preparation is immersed in physiological salt solution at about 

 2030 C. These experiments involuntarily recall Matteucci's 

 statement of the effect of cooling upon the muscle current. 

 Without denying this, we must however point out the enormous 

 difference in degree which is apparent in either direction, in the 

 two cases. The " rest current " of the muscle (i.e. the demarca^ 

 tion current of Hermann) is certainly weakened by intense cool- 

 ing, but is never abolished, much less reversed in direction. 



We have 'found that preparations of the tongue, which, when 

 freshly examined, exhibit strong electromotive action in the normal 

 direction, afford reversed currents less readily on cooling than 

 those whose activity, from long immersion at a not unduly high 

 temperature, is already considerably diminished. Thus we found 

 throughout that the frogs best suited to these experiments had, in 

 every case been kept for a long time during the winter in a warm 

 room. " Cold frogs " nearly always afforded preparations, which if 

 freshly examined gave very strong and comparatively constant 

 currents, opposing, as it were, a greater resistance to the influence 

 of cooling than the equally strong, or even stronger, rest currents 

 of " warm frogs." With this may perhaps be connected the fact that 

 spring frogs packed in snow usually yield a much stronger out- 

 going lingual current than winter frogs. The latter, however, 

 according to our experiences, may be easily thrown into a 

 similarly favourable disposition, if they are kept for two or three 

 days before the experiment in a warm room near the stove. Then 

 on leading off the tongue current the deflection obtained will 

 often be as marked, in the same direction, as in cold frogs, only it 

 is, so to speak, in labile equilibrium. On cooling, it gives way 

 much more quickly to the opposite current than in fresh, cold 

 frogs, where it is sometimes quite impossible to abolish the 

 normal entering current by the methods of cooling described 

 so far. 



This does, however, occur without exception, if melting snow 

 or ice is brought into direct contact with the surface of the 

 mucosa, and we have never met with a case in which, under 

 such conditions, there was not a real reversal of the normal rest 

 current. In detail, however, the reaction in different preparations 

 varies considerably in its proportions, wherein the effect of the con- 

 ditions already cited is once more evident. We have found it most 

 convenient to introduce small, even plates of ice not too thick 



