134 



EXPERIMENTAL PHARMACOLOGY 



on the inhibitory mechanism.) It is usually advisable to 

 take two records of normal vagus inhibition. 



Now start a second round of the tracing and when the 

 new record lacks about one inch of being directly over 



Fig. 125. 



Fig. 126. 



Fig. 125. Injection of drug solutions into the anterior lymph sac of a frog. The 

 narrow point of the injecting pipette is passed into the mouth, and the tongue (which 

 is attached to the front part of the lower jaw) is pushed to one side. The point of the 

 pipette is quickly but gently forced through the muscles in the floor of the mouth. The 

 point will then be felt just beneath the skin over the under jaw. The pipette is now 

 slipped down toward the chest. The skin is attached to the underlying muscles across 

 the sternum but the point is passed through this attachment and into the lymph space 

 in front of the abdomen. The finger is taken off of the upper end of the pipette and 

 the solution is allowed to run slowly into the anterior lymph sac. Do not injure the 

 frog by squeezing it. 



Fig. 126. Injection of solutions into the anterior lymph sac with a small hypodermic 

 syringe. 



the first vagus inhibition record, drop on the heart about 

 ten drops of ten per cent alcohol. How does this affect 

 the beat of the organ? At the moment when the record 



