398 



EXPERIMENTAL PHARMACOLOGY 



it with a pair of pliers. (Pearls, or ampoules, are now pre- 

 pared by several firms already covered by cloth so that 

 glass particles can not fly off from the ampoule when it is 

 broken.) Bring the pearl (or ampoule) up close to the sub- 

 ject's nose and allow the vapors of the drug to be breathed 

 in at once as the glass container is snapped by the pliers. 

 Be sure you already have a normal plethysmographic 

 record started (on a slow drum) before the pearl is broken. 



Fig. 326. Plethysmograph for recording volume changes in the hand and forearm. 

 The rubber band that connects the plethysmograph to the arm may be made of the wrist 

 or arm portion of a rubber glove (which may be bought in a ten cent store). 



The subject should be sitting (or lying) in a perfectly com- 

 fortable position so that he will not move the hand into 

 and out of the plethysmograph while the record is being- 

 taken. The drug is very volatile and in a few seconds it 

 will have practically all disappeared. 



AVhat does your record show ? How do you explain the 

 results? TVhat general sensations does the subject feel? 

 Watch his face and neck closely for any flushing of the skin 



