116 



DR RUTHERFORD ON THE INFLUENCE OF THE VAGUS 



often follows stimulation of the vagus, but such observations must obviously 

 have been utterly fallacious, seeing that violent movements invariably excite the 

 heart's action. With a view to explain how Schiff and his supporters obtained 

 their results, Eckhard* has hinted that possibly the irritating current may have 

 been sent through the vagus so low in the neck that it affected other nerves in 

 addition to the vagus. Certainly Eckhard's conjecture is sufficient to serve as 

 an explanation of the above, but whether or not it be the true explanation, I 

 cannot say, inasmuch as I did not see Schiff and his supporters perform their 

 experiments. 



A striking fact is very clearly brought out by the above mode of experi- 

 menting — viz., that a very much stronger irritant is necessary so to stimulate 

 the cardio-inhibitory fibres of the vagus, that the heart's action may be re- 

 tarded, than is required to stimulate the recurrent laryngeal fibres, so that the 

 laryngeal muscles may be thrown into action. The following table demonstrates 

 this fact : — 



TABLE I. — Showing Comparative Strength of the Stimuli necessary to throw the 

 Inferior Laryngeal and the Inferior Cardiac Nerves into Action. 



No. of Experiment. 



Nature of Animal. 



Vagus Divided in Neck, Lower End Stimulated. 



Distance in Millimetres of Primary from Secondary Coil indicating 



the Weakest Current necessary. 



(A.) To throw the Laryngeal 

 Muscles into Action. 



(B.) To Inhibit the Heart's 

 Action. 



I. 



Rabbit. 



740 



240 



II. 



J5 



550 



130 



III. 



)) 



630 Right Vagus. 



210 



Do. 



;j 



590 Left 



190 



IV. 



J5 



600 



240 



V. 



)* 



575 



220 



VI. 



?J 



650 



250 



VII. 



?) 



520 



170 



VIII. 



7> 



610 



260 



IX. 



)} 



660 



200 



X. 



)> 



630 



210 



XI. 



JJ 



580 



185 



XII. 



?> 



620 



200 



XIII. 



Frog. 



550 



200 



XIV. 





580 



160 



XV. 



)9 



620 



200 



XVI. 



» 



550 



200 



It may be seen, from the above table, that the strength of current necessary 

 to stimulate the inferior laryngeal and inferior cardiac filaments in the trunk of 

 the vagus, differed in different cases. The cause of this is probably threefold : 

 1st, The strength of the electrical current was not absolutely constant ; 2d, The 



Experimental Physiologie des Nervensystems, 1867, p. 201. 



