COKONARY PERFUSION OF EXCISED HEART 9 



II. Dissection. Place the dead rabbit provided for you supine in the iron 

 tray. The following dissection should be done in a good light as rapidly as 

 due care will permit. Make an incision through the skin along the whole 

 length of the sternum and to a point 5 cm. beyond the xiphoid. Rapidly and 

 freely reflect back the skin either side of the incision and retract it with clip- 

 weights. Make carefully with the scalpel a median cut 4 cm. long through 

 the abdominal wall behind the xiphoid. Lift xiphoid and free it by lateral 

 cuts with strong scissors, thrusting one blade through the diaphragm but with- 

 out touching heart or lungs. Cut through with the scissors the cartilages of 

 the lower ribs of each side, well back, to avoid jagged rib-ends injuring the 

 heart. Raising sternum with left hand, cut with the scissors a shield-shaped 

 piece of the front of the chest consisting of posterior 2/3 sternum, the corre- 

 sponding costal cartilages and their rib-ends, and the musculature attached. 

 Pick up the front of pericardium with the fine forceps and open it cautiously 

 with fine scissors. Enlarge opening freely. The venae cavae, pulmonary 

 artery and aorta, and the right and left auricles are to be rapidly identified. 

 Lay preparation on its left side. Draw right lung aside from heart, make out 

 its root, and cut that through with large scissors. Turn the preparation on its 

 right side and similarly cut through root of left lung. 



Make out clearly the aorta and its first large branch, the innominata. Cut 

 through aorta abo ut 5 mm. proximal to innominata. Cut through superior vena 

 cava 1 cm. above right auricle. Tilt apex of heart gently over to left and 

 expose and then cut a snip in it. Carefully pass the packing-needle up 

 through inferior cava and through right auricle and out through the cut 

 superior cava. Pull the needle through and leave the string threaded through 

 inf. cava, auricle, and sup. cava. Tie the two ends of the string together. 

 This is to help finding later the orifices of the two cavae. Cut inferior cava 

 across at the point of entrance of the string. 



Description of Fig. 6 (continued). 



cylinder with o' supply-tube to the pei fusion-fluid reservoirs, b, reservoir for warm or cold 

 water supplying thin glass tube passed through right auricle from superior vena cava to 

 inferior vena cava (experiment on warming or cooling the * pace-maker '). 



2. Gunn's apparatus shown in larger scale {Jnl. of Physiol, xlvi, p. 507, 1913). y, branched 

 glass tube from the two perfusion-fluid reservoirs ; «, glass condenser tube through which 

 warm wat er flows ; p' thin- walled glass tube through which the perfusion fluid flows from y 

 to the aortic cannula h, which fits tightly into the lower end of p'; c c, cork around lower 

 end of p' s ecuring it within lower end of d ; t, thermometer with scale from 0° C. to 50° C 

 lying within and nearly filling p'. 



3. Di agram of heart with aortic stump a tied upon h, the cannula of the perfusion apparatus ; 

 p, pulmonary artery ; r, l, right and left ventricles : g, thin-walled glass tube passing through 

 the superior and inferior venae cavae and attached above to the rubber tube from the 

 reservoir for cold or warm water (for influence of temperature on ' pace-maker '). 



21S1 



