96 



Messrs. Gamgee and Priestley. 



[Feb. 14, 



the vagi were exposed and placed each on a pair of fine platinnm elec- 

 trodes ; and preparations were made for shnnting an interrupted 

 current, by means of a commutator, from one nerve into the other, 

 just as in the case of mammals. Sometimes the heart was watched 

 directly and notes made. At other times care was taken to register 

 the heart's rate, the lapse of time and the moments of stimulation. 

 The heart's rate was indicated by means of Marey's Myographe du 

 coeur* the time by an electromagnet and Ludwig's TJnterbrechungsuhr, 

 and the moments of stimulation by a marking key, each holding a 

 pointed lever against a smoked revolving cylinder. 



The general result of the experiments made by the authors of this 

 paper, is the following : In all the animals hitherto examined (viz., 

 dogs, rabbits and frogs), if one vagus be stimulated powerfully so as at 

 first to arrest the heart, and if after the heart has recommenced to 

 contract, the current be at once shunted to the other vagus, arrest again 

 occurs : in some cases, however, on again reversing to the vagus first 

 stimulated, no effect is produced. This result may be formulated as 

 follows : Stimulation of one vagus never annuls, or even prejudices, 

 the inhibiting powers of the other vagus, unless when the inhibiting 

 apparatus has been recently under stimulation for some time. It would 

 therefore seem that Tarehanoff, in asserting the mutual prejudicial 

 action of vagus- stimulations in mammals, and denying it in frogs, has 

 missed one half of the truth in the case of the former, and the other 

 half in the case of the latter. 



In illustration of their statement of results of experiments, the 

 authors append a reduced kymographic tracing of a dog. The animal 

 was a young terrier, and the experiment was made in the manner 

 above described. The arterial cannula leading to the kymograph was 

 introduced into the femoral artery. 



The upper line is the tracing of the kymograph, the middle line is 

 the line of no pressure, and the lower line is divided into intervals of 

 five seconds. The tracing reads from left to right. Quite at the left 

 of the figure a small portion of the normal tracing is represented. 

 At 2h. 25m. 15s., a stimulus was thrown into the left vagus, the 

 secondary coil being 6 cm. from the primary. At once the heart 

 stopped and the blood-pressure fell. The heart recommenced, and at 

 2h. 25m. 32s. the current was shut off from the nerve. It remained 

 off about 10 seconds, and at the expiration of that interval the current 

 was thrown into the right vagus. Again the heart stopped, and re- 

 mained motionless until 2h. 26m. 25s., a period of 43 seconds, the 

 current, of course, passing the whole of the time. The heart then 

 began to beat, and the blood- pressure rose towards the normal rapidly. 

 At 2h. 26m. 53s. the current was shunted out of the right vagus into 

 the left, the nerve first stimulated, and once more the pulse ceased and 

 * See Marey's " Physiologie Experimentale," II Annee, 1876, p. 70. 



