244 EXPERIMENTAL PHARMACOLOGY 



EXPERIMENT XLIV. 

 Caffeine. (Frog: Heart and Vagus Nerve.) 



1. Take a normal heart tracing from a pithed frog 

 (showing vagus and crescent inhibition). Drop caffeine 

 (saturated solution) on the heart and record the effects. 

 Stimulate the vagus nerve and note the action of the drug 

 on the inhibitory nervous mechanisms. Apply more drug 

 and again stimulate. Stimulate the crescent also and see 

 if it is affected. Take several rounds of the tracing on the 

 drum to get a good insight into the action of the drug on 

 the heart muscle. How does this compare with the action 

 on the mammalian heart ? 



EXPERIMENT XLV. 

 Caffeine. (Turtle: Heart and Vagus Nerve.) 



1. Repeat the previous experiment on a pithed turtle. 

 Can vou see anv changes in the tone of the heart muscle 



* V 



as indicated in your records .' 



EXPERIMENT XL VI. 

 Caffeine. (Man: Reaction Time.) 



1. As in Experiment XXXVI (and XIII) determine the 

 normal reaction time of a student. Then allow the stu- 

 dent to drink one or two cups of strong tea or coffee (or 

 take three grains of caffeine powder in capsules) and at 

 intervals of one-half, one hour and one and one-half hours 

 later again take the student's reaction time. "\Vhat do 

 you observe? How do you explain your results? On what 

 parts of the central nervous system has the caffeine acted to 

 produce the results observed? 



