

CIRCULATION OF THE BLOOD. 



the vago-sympathetic nerve with a strong tetanizing current. Is 

 there any inhibition of the heart-beat ? 



Stimulate the sinus while the nicotine effect is still manifest. Is 

 there any inhibition of the heart-beat ? How can you explain the 

 difference "in result between stimulation of the nerve trunk and 

 stimulation of the point of transfer in the sinus ? Upon what part 

 of the nervous mechanism does the nicotine act ? 



Now bathe the heart with a stronger nicotine solution (one per, 

 cent). Note the effect. To what is the effect due ? 



Paint the heart with the pure alkaloid. In which phase does the 

 heart's action cease ? 



7. Ether. Expose the heart of a pithed frog. Connect with 

 cardiograph lever and take a tracing of the normal beat. Shake 

 up some ether with physiological salt solution and bathe the heart 

 with it, while a tracing is being taken. Observe the effect upon 

 the frequency and strength of the beat. Continue the application 

 of the drug and the observation of the beat of the heart. 



Wash the heart with undiluted ether until the beat grows feebler 

 and finally nearly ceases. Wash with physiological saline. 



Can the beats be restored? Repeat the bathing with strong 

 ether until the beats have again nearly ceased and then allow a few 

 drops of a i to 10,000 adrenalin solution to flow on the heart. 

 Result ? 



8. Chloroform. A frog is pithed, as before, and the heart 

 exposed. A tracing of the normal beat is taken as a control. A 

 time tracing, in seconds, is also taken. 



Physiological saline is shaken to saturation with chloroform. 

 While the tracing is continued, the heart is bathed with this mixt- 

 ure. What is the primary effect of the application of the chloro- 

 form? 



Continue the application of the drug. How does the continua- 

 tion of the chloroform application affect the heart-beat ? 



Discontinue the application of the drug and wash the heart with 

 physiological salt solution. Does the heart recover from the effects 

 of the chloroform ? 



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