224 Prof. Bose and Mr. Das. Physiological Investigations with 



be repeated with the isolated preparation. I will only give here accounts of 

 experiments which are entirely new. 



The chemical solution may be applied directly to the pulvinus, or it may 

 be absorbed through the cut end, the absorption being hastened by hydro- 

 static pressure. The normal record is taken after observing precautions 

 which have already been mentioned in subdivision 2. The reaction of a 

 given chemical agent is demonstrated by the changed character of the record. 

 The effect of the drug is found to depend not merely on its chemical nature, 

 but also on the dose. There is another very important factor — that of the 

 tonic condition of the tissue — which is found to modify the result. The 

 influence of this will be realised from the account of an experiment to be 

 given presently, where an identical agent is shown to produce diametrically 

 opposite effects on two specimens, one of which was in a normal, and the 

 other in a sub-tonic, condition. The experiments described below relate to 

 reactions of specimens in a normal condition. 



Hydrogen Peroxide. — This reagent in dilute solution exerts a stimulating 

 action. Normal records were taken after long-continued application of water 1 

 on the pulvinus. The peroxide, as supplied by Messrs. Parke, Davis & Co., 

 was diluted to 1 per cent., and applied to the pulvinus ; this gave rise to an 

 enhancement of response. Ee-application of water reduced the amplitude to 

 the old normal value (fig. 7). 



Fig. 7. — Stimulating action of hydrogen peroxide. 



Barium Chloride— -The action of this agent is very characteristic, inducing 

 great sluggishness in recovery. The preparation had been kept in 1-per- 

 cent, solution of this substance for two hours. After this the first response 

 to a given test-stimulus was taken ; the response was only moderate, and the 



