THE HEART 57 



of the same heart ; and, knowing the muscle of the heart to vary 

 in those different portions, it was more probable that the difference 

 in power of originating the automatic rhythm lay in the heart 

 muscle itself. This was proved to be the case. Gaskell found that 

 small strips of muscle from the different parts of the heart, so small 

 as to contain no ganglion cells, show the same power of developing 

 different rhythms ; a piece of ventricle, for instance, from a well- 

 nourished animal beating for thirty houre. Gaskell, as we have 

 said, explains the different degrees of automatism by the variation 

 in the type of muscle. The more " embryonic " that is, approach- 

 ing the type seen in the embryo possesses the greatest automatic 

 power. This being the case, then stimulation of the musculature 

 of the sinus or of the auricular ring should originate a series of 

 contractions. Gaskell showed this to be so, proving conclusivsly 

 at the same time that the experiment of Kaiser in regard to the 

 function of Bidder's ganglia was incorrect. 



Gaskell's result may be summarised as follows : 



Stimulation of auricle or ventricle . . One contraction. 

 Stimulation of Bidder's ganglia . . No contraction. 

 Stimulation of the auricular ring . . Series of contractions. 



Consequently the ring musculature and not the ganglia were con- 

 cerned in originating the rhythm. Further support in this direc- 

 tion came from Munk, who also showed that a series of contractions 

 was the normal response to the excitation of this musculature. 

 Ewald found and confirmed by microscopic examination that in 

 only two cases out of twenty-nine were the ganglion cells or nerves 

 injured as the result of the excitation of the ring musculature, 

 which, however, in all cases responded with a series of contractions. 



In the twenty-five years following Gaskell's first work much 

 has been done in endeavouring to support the myogenic con- 

 tention. Engelmann and his pupils have been particularly 

 strenuous in upholding it. During this time, however, the neuro- 

 genic school have provided but little new evidence for their some- 

 what slenderly-founded theory, their chief work consisting in 

 endeavours to refute the evidence brought forward by the 

 myogenic school. The chief points which have been offered as 

 evidence are : 



(1) Engelmann isolated portions of the great veins said to 

 contain no ganglion cells and showed that they beat automati- 



