300 PHYSIOLOGY CHAP. 



(a) When a ligature is applied at any height of the auricle, 

 between the opening of the sinus venosus into the right auricle, 

 and the region nearest the auriculo- ventricular junction, arrest of 

 the heart is, ipso facto, produced in all parts below the ligature, 

 while above, in the sinus and the part of the auricle that is not 

 blocked, the rhythm is undisturbed. 



(b) When a second ligature is applied to the auriculo- 

 ventricular groove in a heart that has been arrested by the first 

 ligature, the ventricle begins to beat again, even though much 

 more slowly than the normal, while the auricles still remain 

 motionless. 



Eckhard (1858-60) showed that practically the same results 

 were obtained by making incisions in the frog's heart, as by the 

 method of Stannius. At the same time he denied their supposed 

 constancy, and found a great variety of effect both from ligation 

 and from sections, in accordance with fluctuations of external 

 temperature, and the varying sensitivity of the preparation, and 

 more particularly of the different regions operated on. He 

 confirmed the fact already observed by Heidenhain that the 

 arrest of the heart produced by the ligature or section is not 

 permanent, for the beats invariably recommence after a longer or 

 shorter pause (lasting from a few minutes to an hour). 



None of the several hypotheses advanced in explanation of 

 these facts will bear searching criticism. Eckhard accounts for 

 the effect of the first Stannius ligature on the rhythm of the 

 heart by assuming a sort of nceud vital, represented by Kemak's 

 ganglia. To explain the effects of the second ligature, he assumes 

 that it provokes a certain excitation of Bidder's ganglia. Eemak's 

 ganglia must function automatically, since the spontaneous move- 

 ments of the heart cease when their influence is cut out ; Bidder's 

 ganglia must be reflex in function, since the stimulus of ligaturing 

 the auriculo-ventricular junction is required to throw them into 

 activity. When, in fact, instead of ligation, an incision is made 

 in this region, which would not have much excitatory effect on 

 Bidder's ganglia, permanent standstill of the ventricle, usually 

 preceded by only 8-10 beats, is produced. 



This theory, which involves a specific differentiation of the 

 cardiac ganglia into automatic and reflex, is unsatisfactory. In 

 order to defend it, we must assume that the upper Stannius 

 ligature has, for its sole effect, the physiological exclusion of 

 Kemak's automatic ganglia, and that the lower ligature on the 

 contrary causes the reflex excitation of Bidder's ganglia. 



We attacked this question in Ludwig's laboratory in 1872, and 

 saw that when the ligature was applied to the frog's heart, after 

 the insertion of a simple cannula, with its point projecting into 

 the ventricle, the same effects were obtained as with the Stannius 

 ligatures. But when the cannula was filled with fresh rabbit's or 



