1881.] On the Physio logical' Action of /3 Lutidine. 



167 



of poisons on the heart one naturally turns to trying their effect upon 

 the vagus. Under ordinary conditions this nerve has the effect when 

 slightly stimulated of slowing, when strongly stimulated of stopping 

 the heart's beat. 



The apparatus used was the moist chamber before described, with 

 the addition of a pair of platinum electrodes connected with the 

 secondary coil of a Du Bois Raymond's induction apparatus. The 

 key for short-circuiting the secondary current carried a marker to 

 make a tracing on the revolving cylinder, indicating the point of time 

 at which the vagus was stimulated and the duration of the stimulus 

 by a rise in the line traced on the drum. To ensure the constant 

 strength of the stimulus, we always allowed the Daniells' cell to work 

 for about half an hour before using the coil. 



The frog was pithed, the heart and vagus laid bare with as little 

 exposure of the surrounding parts as possible, the lever and moist 

 chamber arranged, and a tracing taken of the normal ventricular 

 beats. The vagus was next stimulated with the secondary coil at 

 various distances from the primary, till one was found at which the 

 heart was slowed and another at which it was stopped. 



Experiments were then made with different quantities of solutions 

 of /3 lutidine of various strengths, from 02 cub. centim. of 2 per cent, 

 to 0*2 cub. centim. of 5 per cent., which were injected into various 

 parts of the body, the best results being obtained by injecting into the 

 lower part of the abdominal cavity. 



In all cases the alkaloid deprived the vagus of its power, when 

 stimulated, to arrest the beat of the heart. 



As an example, a frog was prepared and the vagus found to cause 

 slowing of the heart's beat when stimulated with the secondary at 

 14*5, and stoppage at 14 and 13'5 — a long stoppage at the latter. 

 0*2 cub. centim. of 2 per cent, solution of /3 lutidine were injected 

 into the abdominal cavity near the right leg ; after three minutes the 

 vagus on stimulation had but very slight effect, and after six minutes 

 no action. From time to time the secondary was moved nearer and 

 nearer the primary, but stimulation had little or no effect, and after 

 twenty-five minutes the action was imperceptible even when the 

 secondary coil was right over the primary. 



Reflex Action. 



Our next series of experiments were made to ascertain what effect 

 this alkaloid would have upon reflex action. 



The frogs used had their brains destroyed, with as small a loss of 

 blood as possible, by dividing the spinal cord at the junction of the first 

 vertebra and passing a wire into the skull. The animals were then left 

 for some time to recover from the effects of the operation. The 

 stimulus used was a very weak solution of hydric sulphate, and the 



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