58 THE HEART 



cally ; a small piece (2 cmm.) of the sinus of a frog beat for 

 four days and recorded 17,000 contractions. 



(2) In certain molluscs, arthropods, and tunicates, the heart 

 undoubtedly contains no ganglion cells but possesses automatic 

 rhythm. 



(3) The apex of the mammalian heart, said to have no nerves 

 whatever, shows slow rhythmic contractions. 



(4) The embryonic heart beats when no ganglion cells have 

 invaded the heart, and before the muscle and nerve have become 

 differentiated (His). In the chick, the heart of which pulsates 

 36 hours after the beginning of hatching, no ganglion cells appear 

 until the sixth day ; in the human heart Pflliger saw pulsations at 

 the beginning of the third week, whereas no ganglion cells are said 

 to occur until the end of the fourth or the beginning of the fifth 

 week. Fano found that if he divided the heart of a chick into 

 three or more parts, all the parts pulsated the frequency being 

 greater the nearer the part was to the venous end although, as 

 we have seen, the ventricle at that period was the more excitable. 

 W. His has also found differences in the behaviour of different 

 parts of the heart towards drugs such as muscarine and digitalis, 

 the ventricle being the most affected. The in wandering of the 

 ganglion cells leads to no noticeable effect on this. This being 

 the case, it is difficult to believe that later on they should take 

 over the function of initiating the heart rhythm. 



(5) Hearts can be revived many days after death even the 

 hearts of children dead of disease. In ten such hearts only three 

 gave negative results. The heart of a boy dead of pneumonia 

 revived in all parts 20 hours after death. In the case of the heart 

 of an ape, Hering recovered the heart after 4 hours, and then froze 

 it. After 28 hours 32 minutes the heart was again resuscitated. 

 If now the ganglion cells be the site of origin, then Ringer's fluid 

 must possess the power of enabling them to recover their functions ; 

 but if Ringer's fluid have not this power, then the ganglion cells 

 cannot have the power of automatism. Now Langendorff and 

 others have shown that sympathetic ganglia and fibres die very 

 quickly. Hering found in the rabbit that the pre-ganglionic 

 cervical sympathetic was without action 15 minutes after death, 

 the post-ganglionic 33 minutes after death, the vagus on the heart 

 55 minutes after death. The corresponding times for the cat were 

 11, 26, and 40 minutes. It was not found to be possible to restore 



