LABORATORY MANUAL OF PHYSIOLOGY. 



Now bathe the heart in a ten-per-cent solution of pilocarpine hy- 

 drochlorate. What is the effect upon the beat ? 



Stimulate the nerve. Is there any inhibitory effect ? If so, add 

 more of the pilocarpine solution. Stimulate the nerve again. If 

 there is no inhibition, is there any acceleration ? 



After the heart is again beating slowly, add a few drops of weak 

 atropine solution. What is the result? Add more pilocarpine. 

 Does the atropine effect disappear and the pilocarpine effect reap- 

 pear ? Repeat this alternate treatment with pilocarpine and atro- 

 pine, several times. Explain the action of pilocarpine from the ob- 

 servations thus made. Upon what does the antagonism of the 

 two alkaloids, pilocarpine and atropine, depend ? 



4. Muscarin. Expose the heart and vago-sympathetic nerve 

 of a pithed frog. Take a tracing of the normal heart-beat. Next, 

 take a tracing of the beat while stimulating the nerve. 



Bathe the heart in a ten-per-cent muscarin solution. Compare 

 the effect upon the beat with the pilocarpine effect and with the 

 atropine effect. Stimulate the nerve. Is there any result ? Add a 

 few drops of atropine solution. What is the effect ? Explain. 



5. Digitalin. Prepare a frog as before. Take a tracing of 

 the normal beat and of the beat during vagus stimulation. Apply 

 to the heart a few drops of a saturated solution of digitalin, while 

 a tracing is being taken. Carefully note the effect upon the strength 

 of the beat, the rate of beat, and the change in systole and 

 diastole. 



Continue the application of the alkaloid until the heart ceases to 

 beat. Does the heart stand still in systole or diastole? 



6. Nicotine. Expose heart and vagus nerve in a pithed 

 frog. Make a record of the beat before and during stimulation of 

 the nerve. Note the character of the normal contraction. Now 

 bathe the heart with a o.i-per-cent solution of nicotine in physio- 

 logical saline. Continue the tracing during the application of the 

 drug. What is the effect upon the frequence and strength of the 

 heart-beat ? 



While the heart is still under the influence of the drug, stimulate 



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