310 PHYSIOLOGY CHAP. 



declines from sinus to auricles, from auricles to ventricles. 

 Functional exhaustion is again preceded by the phenomenon of 

 periodic rhythm, or crisis, similar to that described by us for the 

 adult frog's heart. 



(e) We have seen that it is possible to revive the rabbit's heart 

 five days after death, by the artificial circulation through the 

 coronary arteries of suitable nutrient fluids, at a given temperature 

 and pressure (Kuliabko). Now it has been found by experiments 

 on the vitality of the peripheral ganglionic elements in general, 

 that they survive suppression of circulation very imperfectly in 

 comparison with the conducting nerve fibres, and more particularly 

 with the muscle cells. Langendorff demonstrated loss of excitability 

 in the ciliary ganglion immediately after bleeding and death from 

 asphyxia of an animal, and showed that the pre-ganglionic fibres 

 ceased to influence the pupil long before the post-ganglionic. H. 

 E. Hering confirmed this fact (1903), but noted that the excitability 

 of the vagus, and still more of the sympathetic, for the heart, per- 

 sisted for a considerable time after the death of the animal. He 

 further observed that when the cells of the superior cervical 

 ganglion had ceased to function it was impossible to revive it 

 by perfusiou with Ringer's solution, which, however, can restore 

 vagus excitability six hours after the death of the animal, and 

 that of the accelerator fibres after a much longer period (fifty- 

 three hours). If, now, the intracardiac behave like the other 

 sympathetic ganglia, it is evident that the rhythm of the heart, 

 which may be re-established by Ringer's solution as much as six 

 days after death, cannot be due to the ganglia, but must derive 

 from the automatic recovery of the muscle cells. 



The absolute and unconditional value of some of the arguments 

 for the myogenic theory of cardiac rhythm is challenged by the work 

 of Bethe (1903), who adopted an improved technique, based on the 

 staining of nerve elements by methylene blue. According to these 

 observations there is not in the whole body of the frog a muscle 

 richer in nerve fibres than the heart. A fine network: of fibrils 

 from the minutest ganglion cells invests the muscular sheath of the 

 entire myocardium, including the apex of the ventricle. Bethe 

 asserts that the muscles of the auricle in the frog are completely 

 separated from those of the ventricle, just as these last are 

 separated from the muscles of the aortic bulb. The nervous 

 reticulum of the auricles again does not seem to be in direct 

 continuation with that of the ventricle, but is connected with it 

 exclusively, or at least to a great extent, by means of Bidder's 

 ganglia, which, as we have seen, lie in the auriculo-ventricular 



groove. 



On these histological grounds, Bethe ranges himself among the 

 supporters of the neurogenic theory, alleging that while the nervous 

 reticulum of the heart is not the sole incentive to its rhythmic 



