ARTIFICIAL RHYTHM. 189 



persistent rh^^tlim admits of being produced by 

 this means. lu this particular species, the manu- 

 brium never exhibits any spontaneous motion after 

 the ganglia of the nectocalyx have been removed. 

 But if it be nijiped with the forceps, or otherwise 

 irritated, it contracts strongly and suddenly ; it 

 then very slowly and gradually relaxes until it has 

 regained its original k-ngth. After a considerable 

 interval, and without the application of any addi- 

 tional stimulus, it gives another single, sudden, 

 though slight contraction, to be again followed by 

 gradual relaxation and a prolonged interval of 

 repose, which is followed in turn by another con- 

 traction, and so on. These sudden and well-marked 

 contractions occur at intervals of many seconds, 

 and show a decided tendency to rhythmic periodi- 

 city, though the rhythm is not always perfectly 

 exact. This intensely slow rhythm, as the result 

 of injury, may continue for a long time, particu- 

 larly if the injury has been of a severe character. 

 There can be no doubt, therefore, that the mecha- 

 nical (or other) injury in this case acts as a source 

 of constant irritation ; so that here again we have 

 evidence of rhythmic action independent of ganglia, 

 and caused by the alternate exhaustion and re- 

 covery of contractile tissues.* 



* We may pretty safely conclude that ganglia are altogether 

 absent in the manubrium of Sarsia, not only because Schultz 

 has failed to detect them in this organ microscopically, but also 

 because of the complete absence of spontaneity which it mani- 

 fests. I may here mention that this case of the manubrium of 

 Sarsia is precisely analogous to another which I have observed in 

 a widely different tissue, namely, the tongue of the frog. Here, 



