COMPARATIVE ELECTRO-PHYSIOLOGY 



response. The ordinary wood of commerce exhibits no 

 response. The familiar fact that the cut end of a woody 

 stem, when not placed in water immediately, ceases to 

 suck up water, has been supposed to be due solely to 

 the intervention of air-bubbles. From the experiment which 

 I have described, however, it would appear that the death 

 of the exposed tissue by drying must be included here as a 

 factor in this abolition of suction. 



With sap-wood I was 

 also able to obtain the in- 

 dication of galvanometric 

 negativity in response to 

 thermal stimulation. Hot 

 platinum wire was applied 

 at a distance of 5 mm. 

 from the proximal contact. 

 Response was thus due to 

 the transmitted effect of 

 excitation. 



I was next desirous 

 to obtain photographic 

 records of the normal 

 response of living wood 

 and its variations under 

 chemical agents. For this 

 purpose I employed both 

 the electrical and vibrational modes of stimulation. For the 

 first of these, the strip of sap-wood was cut in the form 

 of a two-pronged fork, of which one prong was killed by 

 exposure to the drying influence of the air, while the other 

 was kept alive by immersion in water. The specimen was 

 now placed in water as a whole, in order to moisten the dried 

 half. After this, electrical connections were made in the 

 usual manner with the killed and unkilled ends of the speci- 

 men. On next subjecting it to equi-alternating shocks' 

 response was obtained as induced galvanometric negativity 

 of the living prong. These responses are seen in fig. 216 in 

 the first series of records to the left. Chloroform was next 



FIG. 216. Photographic Record of 

 Electrical Response of Sap-wood 



The normal negative responses seen in the 

 first series are depressed after application 

 of chloroform in the second. 



