400 



EXPERIMENTAL PHARMACOLOGY 



Fig. 328. Tracing made with Dudgeon's sphygmograph showing the normal pulse record 

 and a pulse record as affected by inhaling amyl nitrite. 



changes are produced in the pulse curve? How does the 

 drug produce these? 



EXPERIMENT CXX. 

 Amyl Nitrite. (Student: Corpuscles in Retinal Vessels.) 



1. Obtain a piece of him* glass about four inches square. 

 (It is often better to use two pieces of glass placed together 

 to intensify the color.) Let the subject of the experiment 

 lie down at perfect rest on his back before a large window 

 through which he can see a large expanse of clear blue sky. 

 (The sun should not shine on the student's face or on the 

 blue glass plate.) The student now holds the glass near 

 his face and looks through the glass up into the clear sky. 

 He accommodates his eyes for a long distance and remains 

 as perfectly at rest as possible. Presently a considerable 

 number of small, almost circular, shadowy, ill-defined ob- 

 jects will begin to appear in the field of vision. These ob- 

 jects have a rapid, squirming motion, reminding one of the 

 movements of an angle worm in water. The objects nit 

 into sight suddenly, squirm about for an instant and then 

 suddenly disappear. These objects are believed to be the 



