624 ON THE PHYSIOLOGICAL ACTION OF CASCA BARK. 



during this time the irritability was tested every 5 minutes as 

 before : the rates of increase of the insensibility appeared to be 

 equal above and below the ligatures. 



In this experiment the poison was applied to the terminations 

 of the sensory nerves above the ligature, but not to those below 

 it. Had it possessed any marked power of diminishing the 

 sensibility of these nerves, a stimulus applied above the ligature 

 would have had less effect than one applied below it ; but this 

 was not the case. 



The poison therefore seems to have no action on sensory 

 nerves, at any rate none of a paralyzing character. 



Action on Reflex. 

 Experiment LIII. 



In this experiment the action on reflex was tested by apply- 

 ing a very dilute solution of sulphuric acid to the leg of a frog 

 with its cerebrum destroyed and suspended by its head. Its 

 normal irritability was then tested. The tips of the toes only 

 were immersed in the acid. Contraction was immediate and 

 lasted 3 minutes (right leg). A J c.c. alcoholic solution was 

 then injected ; the animal immediately hung more flaccidly. 

 5 minutes afterwards, on immersing the tip of the toes of the 

 right leg, slight contraction occurred after 63 seconds. A 

 quarter of an hour later, on immersing half the leg, contraction 

 was immediate and lasted 5 seconds ; in 10 minutes more a 

 similar immersion produced contraction after 10 seconds, and 

 5 minutes afterwards after 15 seconds. 50 minutes after the 

 injection of the drug the acid solution produced no reflex move- 

 ments, and only slight ones were excited by pinching. Keflex 

 ceased last in the eyelids 1 hour and 20 minutes after the casca 

 had been injected. 



In Experiment LIII the reflex excitability disappeared very 

 much more quickly than it usually does. 



This might be due to the accion of the drug on the spinal cord 

 itself, or to the cessation of circulation caused by the action of 

 the drug on the heart. 



In order to decide this the following experiment was mada 



