Effects of Morphine on Dog's Heart. 



93 



63 (759) 



The effect of morphine on the mechanism of the dog's heart 

 after removal of one vagus nerve. 



By Alfred E. Cohn. 



[From the Hospital of the Rockefeller Institute for Medical Research, 



New York.] 



When injected intravenously, morphine was shown by v. 

 Egmond to cause cardiac arhythmia in dogs. Einthoven and 

 Meek and Eyster studied the results of such injections electro- 

 cardiographically. Einthoven concluded that these were due to 

 stimulation of the vagus centers. He found complete lack of 

 uniformity in the results. Meek and Eyster believed the effects 

 to be due to disturbances in conduction between sinus and auricle 

 and between auricles and ventricles. 



The similarity of some of Einthoven's curves to those resulting 

 from faradic stimulation of the right vagus nerve and of others 

 from stimulation of the left nerve rendered it probable that 

 morphine sometimes had a preponderating influence on the right 

 and at others on the left vagus nerve and center. Experiments 

 were accordingly carried out in twelve dogs, in six of which the 

 right and in six of which the left vagus nerves were removed 

 aseptically. In 3 morphine was injected before operation. Reg- 

 istration was galvanometric. In three dogs (one right during 

 three attempts and two left during two and three attempts) 

 arhythmia characteristic of morphine poisoning was not obtained. 1 

 In three it was obtained on the first attempt, in five on the second 

 and in one on the third. In five right vagus and in four left vagus 

 dogs injection succeeded and the resulting arhythmias were directly 

 comparable to those obtained on faradic stimulation. In the right 

 vagus dogs the auricles, except for occasional contractions which 

 escaped at long intervals, and also the ventricles ceased to beat. 

 The circulation was carried on by ectopic ventricular contractions. 

 That there was no defect in conduction was shown in a number of 

 ways. In the left vagus dogs the auricles were merely slowed. 

 There was depression in A-V conduction in all of them, — in three 



1 The dogs are named according to the nerve retained. 



