RHYTHMIC RESPONSE IN PLANT AND ANIMAL 



351 



intermediate pause are also seen in the pulsation of Des- 

 modium. I have again shown that periodic rhythms of various 

 degrees of complexity are seen, not only in the pulsations of 

 Desmodium, but also in the multiple responses of Biophytum, 

 and even in the electrical responses in plants. 



(4) Effects of barium salt. — There are agencies, such as 

 internal pressure and certain chemical reagents, which induce 

 regularity of pulsation in 

 irregularly pulsating rhyth- 

 mic tissues. Conversely, 

 there are others, which pro- 

 duce the opposite effect, that 

 is to say, a regular pulsation, 

 after such an application be- 

 comes irregular. 



When the heart pulsations 

 are regular, it is found that 

 addition of Veratrin disturbs 

 the uniformity. Remember- 

 ing the general similarity of the action of Veratrin and barium 

 salts, I applied a 5 per cent, solution of this substance to 

 the pulvinus of Desmodium leaflet, which was executing very 

 regular vibrations. The application of this reagent disturbed 

 the regularity -of the pulsation, and somewhat irregular 



Fig. 151. Effect of Barium Chloride 

 Solution on Desmodium 



The regular pulsation, seen to the left, 

 becomes irregular after application 

 of this reagent. 



mS ' tmM^mt mm m ma ■« i w > 



Fig. 152. Arrest of Beat of Ventricle of Frog at Diastole by Application 

 of Acid at Arrow 



Record to be read from right to left (Gaskell). 



groupings were at once established (fig. 151). In another ex- 

 periment with the same reagent, as the application of heat is 

 known to neutralise the action induced by Veratrin and barium 

 salts, I raised the temperature of the plant chamber, with the 

 result that the beats became regular once more. 



