( 90 ) 



At Naples, in 1845, at the Congress of Italian scientists, 

 E. H. Weber communicated the results obtained by himself and his 

 brother Eduard by applying tetanizing induction shocks to the 

 peripheral end of the vagus. Having regard to the fundamental 

 importance of this experiment on " inhibition," I shall refer 

 somewhat fully to this matter. I have not seen the original com- 

 munication. It is published in an Italian journal (Omodei, Annali 

 di Medicina). The following condensed account is based on the 

 Article, Muskelbewegang, in Wagner's Handwortevb. d. P//i/sio/o<fie, 

 Vol. III., pt. 2, p. 42, 1846. 



" My brother and I found that stimulation of the nervi vayi, or of the parts of the 

 brain from which they arise, causes slowing in the tempo of the rhythmical beats of the 

 heart, or even causes the heart to stand still. This is the first experimental proof that 

 the brain acts on the heart, that this action is due to the action of a nerve, which up to 

 this time was not known to be connected with the action of the heart ; that a nerve 

 acting on a muscular organ does not cause movement of that muscle, but arrests — 

 inhibits — a movement, is an altogether new and unexpected fact." " We used a magneto- 

 electric apparatus. One pole was placed on the nose of a frog, the other on a cross 

 section of the cord at the level of the fourth vertebra. On stimulating, after a beat or 

 two, the heart ceased to beat, and remained quiescent for a few seconds after cessation 

 of the stimuli. The heart began to l>eat first at one point, and feebly, and then finally 

 resumed its normal beat. During the period of standstill of the heart, it was not 

 contracted, but in diastole. It was flattened, soft, and gradually filled with blood. 

 To ascertain which part of the central nervous system exerted this effect, the cord 

 was divided at the occiput, and again stimulated, and with the same result, the 

 poles being applied directly to the divided bulb. Another experiment showed that 

 this inhibitory effect was obtained by applying the poles of the magneto-rotatory 

 apparatus to any part, from the corpora quadrigemina to the calamus scriptorius. 

 We found that the vagi were the channels of communication, and the action of both 

 vagi was regarded as necessary to arrest the heart's action." [We know this is 

 inaccurate, for shortly afterwards Budge (1846), M. Schiff (1849), and Ludwig and 

 Hoffa (1849) arrested the heart's beat on stimulating one vagus in the frog, rabbit, and 

 dog. The Webers obtained similar results in warm-blooded animals.] 



We need not pursue this aspect of the question further here, 

 but before the full significance of the action of vagus in the heart 

 could be studied much had to happen. 



By the introduction of the graphic method, in 1847, by Ludwig, 

 i.e , two years after this discovery of the Webers, it became possible 

 to record the effects of a make and break shock of a galvanic current. 

 To get the full vagus effect rapid shocks were required. Indeed, 

 Volkmann, in 1838, had used a rapidly interrupted galvanic current, 

 but his results were unheeded. 



IT was M. FARADAY'S discovery of induced electricity that 

 made the application of rapidly repeated induction shock 

 possible. This came effectively through the convenient and 

 now universally employed inductorium of Du Bois-Reymond. 



