338 



COMPARATIVE ELECTRO-PHYSIOLOGY 



We now return to the question of the normal response of 

 the pitcher in its three different conditions. Of these, in the 

 youngest, no flies are present ; such a specimen will be 

 known as 'fresh.' In others, somewhat older, are a few 

 insects. These pitchers may be regarded as moderately 

 excited, owing either to the struggles of the insects or to the 

 supply of food, or to both. Still another class is found, in 

 which the glandular part of the inner surface of the pitcher is 

 practically coated with captured insects, and has thus already 



been subjected to long- 

 continued stimulation. 

 The responses of these 

 three classes of specimens 

 are in each case, as I shall 

 show, very characteristic. 

 I shall first describe 

 experiments carried out 

 on fresh specimens. 

 Records were made of 

 their responses to equi- 

 alternating shocks of 

 moderate intensity, at 

 intervals of two minutes. 

 The responsive current 

 was here found to flow 



. 

 from the internal glan- 



FIG. 203. Photographic Record of Series 

 of Normal Negative Responses of Glan- 

 dular Surface of Nepenthe in Fresh Con- 

 dition to Equi-alternating Electric 

 Shocks given at Intervals of Two Minutes 



Responsive current from internal glandular 

 to external non-glandular surface. Note 



dular to the external "on- 

 glandular surface. Fig. 



203 gives a series of such responses. It was said at the 

 beginning that the responses of digestive organs were likely 

 to be multiple. This is seen to be true even under the 

 moderate stimulus applied in the present case. But under 

 the action of stronger stimulus, such as that of a thermal 

 shock, the response is found to consist of a long and multiple 

 series, records of which will be seen later. 



Another peculiarity to be noticed, in the series of re- 

 sponses given in fig. 203, is that the base-line of the record 



