458 EXPERIMENTAL PHARMACOLOGY 



At one minute intervals after the drug is swallowed test 

 the saliva (on a white pill tile or glass plate on a sheet of 

 paper) by adding saliva to three per cent starch paste 

 (slightly acidified by HX0 3 ). A positive test should ap- 

 pear within ten to fifteen minutes if absorption be normal. 



Test the urine by adding a few drops of chlorine water 

 and starch solution. What conclusions can you draw? 



EXPERIMENT CLXIII. 



Alkalies, Acids, Sodium Nitrite, Adrenaline. (Frog: Per- 



fusion of Vessels.) 



1. Pith a frog, expose its heart and tie a fine cannula into 

 one aorta (pointing away from the heart) including the 

 other aorta in the ligature. Hang the frog up by the lower 

 jaw and place a graduated cylinder beneath the animal. 

 By means of a Y-tube connect two funnels (or small bottles 

 with outlets at the bottom) to the cannula in the aorta. 

 Suspend the funnels or bottles at a height of six or seven 

 inches above the heart. One funnel (or bottle) is filled with 

 XaOH solution (one-tenth per cent in Ringer's or tapwater 

 saline solution) and the other with HC1 solution (one-tenth 

 per cent in Ringer's or tapwater saline solution). Snip the 

 sinus venosus so that the fluid can pass through the entire 

 system of blood vessels from the beginning of the aorta. Be 

 sure all the air is out of the tubes and that the flow of each 

 solution can be stopped or started by means of clips on the 

 connecting tubes. Fill the tubes with the acid solution and 

 start the perfusion. Catch the outflow below the frog in 

 the graduated cylinder and determine its amount for three 

 or five minute intervals. 



Then change to the alkali solution and measure the out- 

 flow for a corresponding length of time. "Which substance 

 dilates the arterioles? 



Empty out the acid solution and substitute therefor 

 Ringer's solution containing one-half per cent sodium ni- 



