PHA KM A CO LOG Y. 301 



the cardiac fibers carrying impulses centrifugally, 

 could this altered excitability be due to central 

 action of the digitalis? 



(2) After morphinizing dog, fasten firmly to dog board 

 and lightly anaesthetize; expose femoral artery. 



Having placed mercury in the manometer, and 

 filled the cannula, connecting tube and short arm of the 

 manometer with ^ saturated sodic sulphate solu- 

 tion, to prevent clotting, insert the cannula into the 

 femoral artery, in a direction toward the heart. There 

 must be no air bubbles in the apparatus at any point. 

 Let the float, carrying the tracing point, rest on the 

 mercury in the long arm of the manometer and record 

 on the revolving drum. 



The anaesthetic should be discontinued as soon as 

 the cannula is inserted into the femoral artery. Take 

 normal tracing. Now give the dog 0.6 c. c. tr. digitalis 

 hypodermically. 



(0) Watch effect on elevation of float, making trac- 

 ings at short intervals. 



(^) What elements enter into arterial tension ? 

 (c) How does a " high tension " tracing differ from 



a "low tenison" tracing? 

 (</) How do changes in tension affect the elevation 



of the tracing above the abscissa ? 

 (e) What effect has digitalis on arterial tension ? 



(3) Having firmly fastened a pithed frog to frog board 

 with web stretched over a cover glass fastened into a 

 hole in the board by means of sealing wax, focus the 

 microscope upon a certain arteriole in the field, and 

 measure its diameter with an eyepiece micrometer. 

 Now inject into dorsal lymph spaces 0.3 c. c. tr. digi 

 talis and measure same arteriole 



