SENSITIVENESS OF PLANT AND ANIMAL 251 



and discoloured, and ceases to exhibit its normal motility. 

 The only alternative has been to grow the plant in the 

 suburbs and bring it to the laboratory. Here, with one or 

 two days' rest after the disturbing effect of transport, it 

 regains a fair degree of sensitiveness, but the effect of the 

 air of the town is to bring about a daily deterioration, and 

 in the course of a week or ten days, except in rare cases, it 

 becomes practically insensitive. It will thus be seen that 

 the experimental plant employed for our comparison may be 

 taken as having had its sensitiveness reduced certainly to 

 half. 



In proceeding with the experiment, according to the 

 method already described, it was found that the nerve-and- 

 muscle preparation responded at the make of a current 

 which was as feeble as -25 micro-ampere. The Biophytum 

 at this time had not yet responded, but when the current 

 intensity was increased to -5 micro-ampere excitation was 

 seen to occur. From this it would appear that Biophytum 

 had in this case fully half the susceptibility of the nerve-and- 

 muscle preparation of frog. Bearing in mind the peculiarly 

 unfavourable character of the circumstances to which the 

 plant was in this case subjected, it does not seem too much 

 to infer that the sensitiveness of the two specimens was 

 not naturally of a different order. 



It might perhaps be still more interesting to institute a 

 comparison between the intact plant and the intact human 

 subject. The tongue has always been considered a very 

 sensitive detector of electrical current. According to 

 Laserstein, the acid effect of anode is appreciated by it 

 when the current is only yi^ of a milliampere. This is 

 equal to 6-4 micro-amperes. 



But I have found amongst my pupils some who could 

 perceive by the tongue a current as feeble as 1*5 micro- 

 ampere, whereas the Biophytum in the same circuit responded 

 to the much smaller current of '5 micro-ampere only. This 

 demonstrates that the plant was in this case three times as 

 sensitive as the human tongue. A more excitable specimen 



