418 EXPERIMENTAL PHARMACOLOGY 



After a time kill the animal with a large dose of one of 

 the drugs if it has not already died as indicated above. 

 AVatch the heart closely throughout the experiment and see 

 if you can follow the changes occurring in the auricles and 

 ventricles. If delirium cordis sets in which chambers are 

 affected by it first? Is this of any clinical significance? 

 Can you detect this on the carotid record! AA^ould this 

 signify anything of importance from a clinical standpoint 1 

 Are the vagus endings in the heart paralyzed during the 

 third stage? Could you determine this point during your 

 experiment in any way! 



EXPERIMENT CXXX. 

 Digitoxin. (Dog: Heart Tracings, Carotid Pressure.) 



1. Arrange a dog for recording tracings from both auri- 

 cle and ventricle as Avas done in previous experiments. If 

 simple heart levers are used the right auricle and right ven- 

 tricle will probably be the easier for the student record. If 

 a Cushny myocardiograph is available the left ventricle 

 can very well be used. If only one chamber can be recorded 

 then the left ventricle is preferred. 



The records should be arranged with the auricular tracing 

 at the top of the drum, below this the ventricular tracing, 

 then the carotid pressure, and finally the base line (show- 

 ing the time also). The injecting burette contains digitoxin 

 (five cubic centimeters equal one milligram). 



AAlien all adjustments are made take a normal record and 

 begin to inject digitoxin in very small repeated doses, wait- 

 ing a little while between each dose to see what its effect 

 will be. The object now is to bring on the action of the 

 drug slowly and to watch to record the changes in each 

 chamber as the three stages develop. AAlien the marked 

 slowing of the second stage first begins to appear (due to 

 stimulation of the inhibitory center in the medulla) watch 

 carefullv to see whether the auricles or ventricles first 



