336 PROTOPLASMIC ACTION AND NERVOUS ACTION 



their intimate connection with the metabolic reactions 

 of the living protoplasm is thus indicated. 



In the frog's muscle the rhythmical character of the 

 bioelectric current during tetanic contraction is most 

 readily demonstrated by the '^ secondary tetanus" 

 experiment, in which a muscle with its nerve laid along 

 another muscle is thrown into tetanus when the second 

 muscle is tetanized. In man, the slight mechanical 

 oscillation accompanying steady voluntary contraction 

 of the arm muscles can be demonstrated by means of 

 the hot-wire sphygmograph ; this mechanical rhythm has 

 the same period as the electromotor rhythm; i.e., about 

 fifty per second.' This experiment is especially interest- 

 ing as indicating (as do also the experiments with the 

 string galvanometer) that the various nerve cells iner- 

 vating a muscle discharge synchronously or in phase with 

 one another. The experiments of Gasser and Newcomer 

 also indicate that this is true of the nerve cells innervating 

 the opposite halves of the mammahan diaphragm.^ 

 Apparently the several nerve cells constituting each 

 motor group are under some control by which all are 

 impelled to react synchronously, or ''keep time." This 

 suggests a co-ordination dependent on some rapidly 

 transmitted influence, presumably electrical; the syn- 

 chronous activity of spermatozoa when gathered in 

 clumps, or of cihated cells, seems to be a phenomenon 

 of a closely related kind (see p. 392). 



'A. V. Hill, Journal of Physiology, LV (192 1), Proceedings of the 

 Physiological Society, p. 14. 



' Gasser and Newcomer, op. ciL, p. 24. 



