254 



PHYSIOLOGY OF THE HEART. 



[CH. xx. 



muscular tissue itself, though normally during life it is controlled 

 and regulated by the nerves that supply it. 



The intracardiac nerves have been chiefly studied in the frog ; 

 the two vago-sympathetic nerves terminate in various groups of 

 ganglion cells ; of these the most important are Remak's ganglion, 

 situated at the junction of the sinus with the right auricle ; and 

 Bidder's ganglion, at the junction of the auricles and ventricle. A 

 third collection of ganglion cells (von Bezold's ganglion) is situated 

 in the inter-auricular septum. From the ganglion cells, fibres 

 spread out over the walls of sinus, auricles, and the upper part 

 of the ventricle. Remak's ganglion used to be called the local 



inhibitory centre of the heart ; 

 it is really the termination 

 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 

 the local accelerator 

 for a corresponding 



called 

 centre 

 reason. 

 The 



Fig. 251. Course of the nerves in the auricu- 

 lar partition wall of the heart of a frog. 

 d, dorsal branch ; v, ventral branch. 

 (Ecker.) 



accompanying figures 

 show the vagal terminations 

 in Remak's ganglion (fig. 

 251), some isolated nerve- 

 cells from this ganglion (fig. 

 252); and fig. 253 is a 

 rough diagram to indicate 

 the positions of the principal 

 ganglia. 



In connection with the rhythmic contraction of the heart, it is 

 necessary to allude to what is known as Stannius' experiment. 

 This experiment consists in applying a tight ligature to the heart 

 between the sinus and the right auricle, the effect of which is to 

 stop the beat of the heart beyond the ligature, whilst the sinus 

 continues to beat. If a second ligature is applied at the junc- 

 tion of the auricles and ventricle, the ventricle begins to beat, 

 whilst the auricles continue quiescent. In both cases the quies- 

 cent parts of the heart may be made to give single contractions 

 in response to mechanical or electrical stimulation. A consider- 

 able amount of discussion has arisen as to the explanation of 

 these phenomena. It was suggested that the action of the 

 ligature is to stimulate the inhibitory nervous mechanism in 



