ADVANCED EXPERIMENTAL PHYSIOLOGY 159 



Perfusion of Frog's Blood-vessels. Destroy the cerebrum and 

 expose the heart. Tie one aorta. Place a ligature under the 

 other, snip it with sharp scissors, and allow the blood to escape. 

 Insert a fine-glass cannula into it pointing away from the heart. 

 Fill the cannula with normal saline by means of a capillary pipette. 

 Connect a rubber tube to a glass funnel and clip the tube. Fill 

 the funnel and tube with Ringer's fluid. Connect the tube with 

 the cannula. No air bubbles must be introduced. Snip the sinus 

 venosus and open the clip. Hang the frog in the vertical position. 

 The fluid circulates, runs out of the sinus, and drops from the toes 

 of the frog into a measure glass. Measure the outflow per minute. 

 Circulate Ringer's fluid plus 1 in 1000 sodium nitrate ; the outflow 

 is increased owing to vaso- dilatation. Supra-renal extract produces 

 the opposite effect. 



CHAPTER XXXIII 

 CIRCULATION OF THE BLOOD 



Proofs of the Circulation of the Blood. The following experi- 

 ments should be performed upon a decerebrate mammal. A decapi- 

 tated duck is very useful owing to the great length of neck for 

 dissection and the ease with which cardiographic records of the 

 ventricular contractions may be taken. 



The external jugular vein and the carotid artery are exposed 

 and the conditions as regards pressure and pulsation in these 

 vessels are determined carefully by the fingers. A clip is placed 

 on the jugular vein, the central end becomes empty, the peripheral 

 end engorged. The clip is placed next on the carotid artery, the 

 central end becomes distended and pulsates, while the peripheral 

 end shrinks and ceases to pulsate. The clip is removed and two 

 double ligatures are placed in position under each vessel. The 

 vein is pricked ; dark blood flows out from the peripheral end 

 steadily and with little force. The vein is ligatured above and 

 below the opening. The artery is pricked ; bright blood spurts 

 out forcibly and in jets from the central end. The artery is liga- 

 tured above and below the opening. 



A cannula is placed in the trachea and connected with the appara- 

 tus for artificial respiration. The sternum is divided in the mid- 

 line, and the thorax opened. Observe the inflation and elasticity 

 of the lungs and the contraction of the heart inside the pericardium ; 

 feel with the thumb and finger the contraction and relaxation of 

 the ventricles. Slit open the pericardium and observe the heart. 

 Ligatures are passed under the superior and inferior venae cavae 

 and tightened ; the heart quickly becomes empty. Loosen the 

 ligatures and observe the immediate filling of the right side of the 

 heart. Now a ligature is passed under the aorta and tightened ; 

 the left and then the right side of the heart becomes engorged, 



