Why Does the Heart Beat? 



By R. W. TOWER and C. F. HERM 



WHY does the heart beat? It is a 

 question not altogether easy to 

 answer. Perhaps there is no adult 

 who has not counted his own or 

 another's pulse and wondered at the regu- 

 larity of the rhythm with which the phenom- 

 enon proceeds. Doubtless every one who 

 has dressed his own catch after a successful 

 fishing trip has observed how the heart of the 

 animal beats for some time after it has been 

 removed from the l)ody, and has asked him- 

 self: Why this activity and how is it con- 

 trolled? Is this rhythmic contraction of the 

 heart muscles, continuing day after day, 

 year after year, dependent upon factors out- 

 side of the heart, upon stimulations carried 

 to it over nerves from other organs of the 

 body, or is it of an automatic nature, depend- 

 ing upon conditions and stimulations from 

 within the organ — a function of the very 

 heart cells themselves? The answers have 

 been as many and varied as there have been 

 questions. 



The problem is difficult and complicated. 

 That the heart of a cold-blooded animal will 

 continue to beat some time after being taken 

 from the body has been observed by almost 

 every one, but this proves nothing. That 

 the activity of the heart is regulated by nerve 

 centers outside of itself is undoubtedly true, 

 but this in no way concerns the cause of the 

 rhythmical contraction. It is well known 

 however, that there are within the organ 

 numerous nerve cells which, although cut off 

 from their central office, yet through their 

 natural properties might cause the systematic 

 beating. 



The cause may also be sought in the nature 

 of the muscle itself, in which case it is assumed 

 that the muscle cells possess the inherent 

 quality of contraction. Many experiments 

 have been performed to solve this interesting 

 problem in a convincing manner. Very 

 recently it has been found possible to grow 

 heart muscles of a warm-blooded animal in an 

 incubator, and during this growth a single 

 muscle cell has been observed to wander away 

 from the mother tissue and by itself begin to 



1 Observations from the experimental work in the 

 physiological laboratory of the American Museum. 



beat. It would therefore seem that the 

 individual isolated cell, having grown to a 

 certain size and finding the necessary food, 

 the necessary warmth, the necessary oxygen, 

 or in other words the correct environment, 

 will begin to beat — • that is its business, it 

 cannot help it. 



Again, several cells, while growing, may 

 attach themselves one to another forming 

 clusters of various appearances, and these 

 cells after a time begin to beat, not each one 

 separately but all together, the rhythm 

 persisting at perhaps one hundred times a 



Series of single heart-muscle cells which have been 

 observed to grow, beat separately, unite with one 

 another, and finally beat in unison 



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