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A MANUAL OF PHYSIOLOGY 



(2) Heart Tracing, with Simultaneous Record of Auricular 

 Ventricular Contractions. (a) For this purpose two levers may be 

 arranged, one resting on the auricle, the other on the ventricle, the 

 writing points being placed in the same vertical straight line on the 

 drum. A convenient form of apparatus is shown in Fig. 77. 



(b) Gaskell's Method (a modification of). Attach a silk ligature to 

 the very apex of the ventricle. Divide the frsenum, cut the aorta 

 across close to the bulbus, pinch up a tiny portion of the auricle and 

 ligature it. Remove the intestines, liver, lungs, etc., care being 

 taken in cutting away the liver not to injure the sinus. Then 

 remove the lower jaw, and cut away the whole of the body except 

 the head, part of the oesophagus, and the tissue connecting it with 

 the heart. Fix the head in a clamp sliding on an ordinary stand. 

 The heart is held at the auriculo- ventricular junction in a Gaskell's 

 clamp supported on a separate stand. The thread connected with 

 the ventricle is brought round a pulley and attached to a lever 

 above the heart. The auricle is connected with another lever. The 



Auricular 



fo rest on Aurtcte 

 Pad to rest on Ventncte 



FIG. 77. APPARATUS FOR OBTAINING A SIMULTANEOUS TRACING OF 

 AURICULAR AND VENTRICULAR CONTRACTIONS. 



writing-points of the two levers are arranged in a vertical line on the 

 drum. The small pulley must be oiled from time to time to lessen 

 the friction (Fig. 78). 



If tortoises or turtles are available, the much larger heart of these 

 animals may be used for Experiments 5 (2) (a) and (b) . The animal 

 having been killed by cutting off its head, the ventral portion of the 

 carapace is detached by the saw. The pericardium can now be slit 

 open, and the pads of the levers arranged on auricles and ventricle 

 respectively, as in Experiment 5 (2) (a), without further disturbing 

 the heart. Or the heart may be removed, together with the upper 

 portion of the body, the pericardium opened, and the liver cut away. 

 The aortic trunk is then divided, and the portion of it attached to 

 the heart grasped by a small forceps clamp. Fine silk ligatures are 

 attached to the apex of the ventricle and the top of the right auricle. 

 The vagus nerves are exposed in the neck, ligated, and divided. 

 The upper portion of the body is supported on a stand. The forceps 

 grasping the aorta is fixed in an ordinary holder, and the threads are 

 attached to the levers, as in Experiment 5 (2) (b) . 



