522 THE OUTGO OF ENERGY 



loss of pressure between the ventricle and the 

 smallest arteries is relatively slight. 



The pulse is absent on the venous side of the 

 resistance. 



The Curve of Arterial Pressure in the Frog. 

 Expose the heart of a frog, the brain of which has 

 been pithed without haemorrhage. Provide a fine 

 cannula with a short piece of rubber tubing. 

 Fill cannula and tube with one per cent sodic car- 

 bonate solution, and close the end of the tube with 

 a small glass rod. Tie a ligature about one aorta 

 as far as possible from the junction of the two 

 aortse. Knot the ends of the ligature together. 

 Pass a second ligature beneath the same aorta, but 

 do not tie it. Lift the vessel by the second 

 ligature so that the vessel is constricted by lying 

 across the thread. Between the two ligatures 

 open the aorta with sharp scissors and introduce 

 the cannula. Fasten the cannula in place by 

 means of the ligature. Place the frog-board on 

 the wooden stand to bring the heart on a level 

 slightly higher than the level of the mercury in 

 the mercury manometer (Fig. 69). See that the 

 proximal limb of the manometer is filled with 

 one per cent sodic carbonate solution to the ex- 

 clusion of air. Bring the writing point of the 

 manometer against a smoked drum and revolve 

 the drum once by hand to record a line of atmos- 



