ANIMAL ELECTRICITY. LECTURE VL I 33 



sensitive than the latter, and in all the experiments 

 I have made up to this time, an augmentation of K. 

 has been produced by carbonic acid and by tetanisa- 

 tion. This is illustrated in figs. 57 and 58, where 

 both A. and K. alternately produced have been 

 placed under observation. In both cases the K. cur- 

 rent has been obviously increased by carbonic acid 

 and by tetanisation respectively, but the A. current 

 diminished by carbonic acid in fig. 57, exhibits no 

 marked alteration in consequence of tetanisation in 

 fig. 58. Presumably in this last case a mean hap- 

 pens to have been struck between augmentation and 

 diminution. 



The Influence of Temperature. — It is a very 

 simple matter to examine the effect of a raised or 

 lowered temperature upon the extrapolar currents, 

 and the results — in the case of raised temperature 

 at least — are very constant and very characteristic. 

 All we have to do is to place the nerve-chamber in 

 a receptacle that is packed round with ice and salt, 

 or gradually warmed by a spirit-lamp, and then take a 

 continuous observation in the usual way. I shall not 

 tax your patience by asking you to witness such an 

 observation ; to be of any value it would have to be 

 slowly made w^ith the temperature raised or lowered 

 through a range of 20 degrees at a rate of a degree 

 a minute. Moreover, the photographic record gives 

 a better general view of matters than the observation 

 itself, and although less interesting perhaps, is cer- 



