276 CIRCULATION OF THE BLOOD. 



now be removed in the manner directed in 63, care being 

 taken to avoid interfering with the vena? cavae. The glass 

 rod having now been fixed horizontally on the table, and the 

 oesophagus secured by pins stuck through it into the table so 

 as to prevent it from slipping on the rod, the apex of the 

 heart is seized with blunt forceps and drawn forwards and to 

 the right. A silk ligature is then passed, with the aid of the 

 needle shown in fig. 2036, between the vena cava inferior and 

 the ventricle, and between the venre carte superiores and the 

 right auricle, in such a position that when it is tightened it 

 will grasp the line of junction between the sinus venosus 

 and the right auricle. The ligature having been looped by nn 

 assistant and carefully adjusted in the proper position, the 

 heart is left to itself. As soon as it is seen that it is con- 

 tracting regularly, the ligature is tightened. After one or two 

 beats, the heart stops in a state of relaxation. The pulsations 

 of the sinus, however, continue at the same rate as before. 

 After a time the ventricle also begins to beat ; but on com- 

 paring its rhythm with that of the sinus, it is seen that they 

 do not agree. 



2. In another heart, prepared in the same manner, the sinus 

 is cut off from the right auricle, the line of amputation corre- 

 sponding with that of the ligature in 1. In doing this, the 

 heart must be drawn forwards with the forceps by its apex as 

 above directed. The result is more striking when the scissors 

 used are not very sharp. 



3. If in either of the above experiments the ventricle is cut 

 off from the auricles immediately after the ligature or amputa- 

 tion, as the case may be, it begins to beat again at once. 



4. In a third heart, the line of ligature, i. e., the junction 

 between the sinus venosus and the right auricle, is excited by 

 the induced current. For this purpose Du Bois Re3'inond's 

 induction apparatus is used. The points of the excitor must 

 be very close to each other. The effect resembles that of the 

 ligature. If the electrodes, instead of being placed so as to 

 include the sinus, are applied to the auricles, no effect is 

 produced. 



5. In another animal, y^^ of a grain of atropin (or less) is 

 injected underneath the skin. After a few minutes the heart 

 is removed, and experiment 4 is repeated. The electrical exci- 

 tation produces no effect, the ganglion of the septa being para- 

 lyzed. Experiment 1 is then repeated. The heart stops as 

 before. 



All the preceding results can be obtained in the separated 

 heart. The method recommended facilitates the manipulation 

 without in the slightest degree impairing the value of the re- 

 sults. Stannius's experiment admits of two different explana- 

 tions, which are not, however, inconsistent with each other: 



