140 APPLIED PHYSIOLOGY 



tricular excitability. The former has been likened to a 

 man who stumbles because he is lame, the latter to one 

 whose gait is irregular because he is on rough ground. 

 The first may be described as ' arhythmia,' the second as 

 1 pararhythmia ' (Wenckebach). 



4. The last form of irregularity of the cardiac rhythm 

 (allorhythmia) is that due to a want of synchronism in 

 action between the two auricles or two ventricles 

 respectively, or between the two sides of the heart 

 as a whole. A want of complete synchronism in the 

 action of the ventricles is believed to be the clinical 

 explanation of reduplication of the first sound, the 

 tension on the mitral and tricuspid valves reaching its 

 maximum at different moments. Such want of syn- 

 chronism can best be explained by local alterations in 

 conductivity in different parts of the heart, alterations 

 which might very well be the result of disease affecting 

 the muscle of one ventricle more than that of the other, 

 or to local variations in nervous control.* 



The former is the more likely cause, for the normal 

 synchronism of the ventricles appears to be maintained, 

 not through nervous, but through muscular connections, 

 and to be independent of nerve cells. Further, it is 

 apparently managed by the ventricles themselves, and 

 not by the auricles. t 



* Engelmann, Arch. f. d. Ges. PhysioL, 1896, Ixii. 543. 

 f Porter, ' The Co-ordination of the Ventricles,' Amer. Journ. of 

 Physiol., 1899, ii. 127. 



