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HANDBOOK OF PHYSIOLOGY. 



in the heart of the frog, of the tortoise, and of other cold-blooded 

 animals. 



In the frog's heart (fig. 191) these ganglia consist of three chief 

 groups. The first group is situated in the wall of the sinus venosus 

 at the junction of the sinus with the right auricle (Remak's); the 

 second group is placed near the junction between the auricles and ven- 

 tricle (Bidder's); and the third in the septum between the auricles 

 (v. Bezolcrs). 



The nerve cells of which these ganglia are composed are generally 

 unipolar, and seldom bipolar; sometimes two cells are said to exist in 

 the same envelope, constituting the twin cells of Dogiel. The cells 

 are large, and have very large round nuclei and nucleoli (fig. 193). 

 Ganglion cells have not been found in the lower part of the ventricle. 



As regards the automatic movements 

 of the heart removed from the body our 

 chief knowledge has been derived from 

 the study of the hearts of the frog and 

 tortoise. 



C 



Fig. 192. 



Fig. 193. 



Fig. 192. Course of the nerves in the auricular partition wall of the heart of a frog. d. Dorsal 

 branch; v. ventral branch. (Ecker.) 



Fig. 103. Isolated nerve-cells from the frog's heart. I. Usual form. II. Twin cell. C, Capsule; 

 N, nucleus; N', nucleolus; P, process. (From Ecker.) 



If removed from the body entire, the frog's heart will continue to 

 beat for many hours and even days, and the beat has no apparent differ- 

 ence from the beat of the heart before removal; it will take place, as we 

 have mentioned, without the presence of blood or other fluid within its 

 chambers. Not only is this the case, but the auricles and ventricle may 

 be cut off from the sinus, and both parts continue to pulsate, and fur- 

 ther the auricles may be divided from the ventricle with the same result. 

 If the heart be divided lengthwise, its parts will continue to pulsate 

 rhythmically, and the auricles may be cut up into pieces, and the pieces 

 will continue their movements of rhythmical contraction. 



It will be thus seen that the rhythmical movements appear to be 

 more marked in the parts supplied by the ganglia, as the apical portion 



