468 ELECTRO-PHYSIOLOGY CHAP. 



point, a regular diminution may be observed, with subsequent 

 increase of current. The explanation of these effects can only 

 be given in connection with other facts to be communicated later. 

 The marked effect produced by changes of temperature upon 

 the electromotive action of the frog's tongue claim fuller dis- 

 cussion. If a curarised frog is kept for a long period (several 

 hours) at a low temperature, the tongue, if examined as quickly 

 as possible, will often exhibit a reversed, i.e. outgoing current of rest, 

 which is frequently no less strong than the previous normal 

 incoming current. As a rule, this reversed current diminishes 

 pretty quickly as the preparation gets warmer. A short stage 

 occurs when, under the given conditions of leading off (surface 

 of tongue and exposed muscles of leg), no difference of potential is 

 visible, after which the normal entering current gradually develops. 

 The strongest reversed effects are obtained when weakly curarised 

 frogs are packed in snow for some hours. If the lingual current 

 is then investigated as above in the uninjured animal as quickly 

 as possible, before any heat effect becomes visible, an extraordin- 

 arily strong deflection, far exceeding the scale, may often be 

 seen in the direction of an outgoing current. And if such a " cold 

 frog" is left in a warm room, the normal entering current will 

 develop, as has been shown, more or less quickly. These 

 experiments led to the further testing of heat and cold upon the 

 excised tongue, using throughout the preparation from the lower 

 jaw. Since 0'5 % JSTaCl solution was found to be tolerably 

 indifferent for electromotive action of the tongue, immersion 

 for hours in this fluid producing no noticeable effect, the simplest 

 method of warming or cooling appeared to be to place the 

 preparation in solutions of the same molecular strength at 

 different temperatures. And this showed, without exception, 

 that every preparation that had previously acted strongly in the 

 normal direction now became currentless in the shortest possible 

 interval, developing indeed in most cases a reversed (outgoing) 

 current, provided it were placed on snow in a watch-glass filled 

 with physiological salt solution, and covered with a bell-glass for 

 some hours at low temperature (0-2 C.) The same result is 

 also obtained if the preparation on the clay block is simply 

 placed for several hours in a moist chamber in a cold, but not 

 frosty, room (at about 2-4 C.) In every case the outgoing 

 current of rest can be reversed almost instantaneously if the 



