CH. XX.] 



CONDUCTION IN THE HEART 



253 



the cell-station of the inhibitory fibres, and stimulation of the heart 

 at the sino-auricular junction is the most certain way of obtaining 

 stoppage of the heart. Bidder's ganglion was called the local 

 accelerator centre for a corresponding 

 reason. 



The accompanying figures show the 

 vagal terminations in Eemak's ganglion 

 (fig. 259), some isolated nerve-cells 

 from this ganglion (fig. 260); and fig. 

 261 is a rough diagram to indicate the 

 positions of the two principal ganglia. 



Conduction in the Heart. The 

 question has been discussed whether 

 the wave of contraction is propagated 

 along the heart-wall by nervous or 

 muscular connection. The slow rate 

 of propagation of the wave points to 

 the link being a muscular one, and it 

 will be remembered that histology lends 

 support to this view, the muscular 

 fibres being connected to each other 

 by intercellular bridges of protoplasm 

 (see p. 87). An experimental proof 

 of the same view is the following: if a strip of the heart wall is 

 taken and a number of cuts going nearly completely across it, be 

 made first from one side, then from the other, all the nerves must be 

 cut through at least once, and the only remaining tissue not severed is 



FIG. 259. Course of the nerves in the 

 auricular partition wall of the heart 

 of a frog, d, dorsal branch ; v, ventral 

 branch. (Ecker.) 



Aorta 



FIG. 260. Isolated nerve-cells from the frog's heart. I. Usual 

 form. II. Twin cell. C, capsule ; N, nucleus ; N', nucleolus ; 

 P, process. (From Ecker.) 



FIG. 261. Diagram of ganglia in frog's 

 heart. R. Remak's, B, Bidder's 

 ganglion ; S, sinus ; A, right auricle; 

 V, ventricle. 



muscular, yet the strip still continues to beat ; in other words, the pro- 

 pagation is myodromic. The passage of the wave from one chamber 

 to another is also myodromic. The slow rate of propagation indicates 

 that this is so, and the view has been fully proved by the discovery 

 of muscular fibres passing across from one chamber to the next. 



