ACTION OF ATROPINE 



them and place the foot in such a manner that a good light 

 can fall at a slight angle on to the pads. A hand lens may 

 be used to considerable advantage. Stimulate the corre- 

 sponding sciatic nerve and watch for minute droplets of 

 sweat to form on the pads. On that side of the animal it is 

 advisable not to place a cannula in the femoral vein but in- 

 sert the cannula in the external jugular vein instead. Do 

 not injure the circulation in isolating the sciatic nerve. 



Arrange all writing points on the drum (medium speed) 

 and while taking a normal (satisfactory) record begin to 

 stimulate one vagus nerve with a weak or medium strength 

 of current (tetanizing). The current should be of just great 

 enough strength to slow the heart markedly but not to com- 

 pletely stop it. Do not continue this any longer than neces- 

 sary or the vagus endings may be worn out. While thus 

 holding the heart down to a slow rate by a constant stimula- 

 tion (increase the strength of the current if necessary) of 

 the nerve inject two cubic centimeters of atropine solution 

 (for a dog, if a cat or rabbit is used inject one-half or one 

 cubic centimeter of atropine solution). 



Continue the stimulation. Do you observe any change 

 after the drug has had time to be carried to the heart in 

 the blood? (Remember the circulation is slow and sluggish 

 when the heart beats but slowly and the pressure is low). 

 How do you explain your findings? Now inject another 

 dose of atropine as soon as the animal can tolerate it. Then 

 stimulate the opposite vagus nerve and note the effect on 

 the heart rate and blood-pressure. Stimulate the chorda 

 tympani and note the effect on salivary secretion. How do 

 you explain this? 



Examine the sole of the foot (dog) carefully for sweat 

 droplets (remove these if any are present) and then stimu- 

 late the sciatic again. What conclusions can you draw? 

 Were you able to get a sweat secretion by stimulation of the 

 sciatic before the drug was injected? If not what does this 

 part of the experiment show? Again stimulate one vagus 



