GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 151 



the rapidly following excitations applied to .1 was the cause of a separate eon- 

 traction process and a separate current of action in B; the separate contractions 



combined to produce the tetanus of B, but the separate currents of action did 

 not fuse, although they caused a continuous negative variation of the slowly 

 moving magnet of the galvanometer. 



The correctness of this view has been shown by experiments with the capil- 

 lary electrometer, which approaches the " physiological rheoscope/' as the 

 nerve-muscle preparation is called, in its sensitiveness to rapid changes in elec- 

 trical potential. 



Burdon Sanderson 1 has obtained, by photographically recording the move- 

 ments of the column of mercury of the capillary electrometer (see Fig. 63, 

 p. 146), beautiful records of the changes of electric potential which occur when 

 an injured muscle is tetanized. 



The record in Figure Q6 shows, first, a series of negative changes resulting 

 from the separate stimuli. It is these which cause secondary tetanus and 

 which produced the negative variation current disclosed by the galvanometer 

 in the experiments of Du Bois-Reymond. Second, there is a more permanent 

 negative change, likewise opposed to and lessening the effect of the negative 

 change at the part where the tissue is dying, and called by Sanderson "the 

 diminutional effect." The continuous uegative change i- possibly attributable 

 to the presence of a continuous contraction process, perhaps the contracture 

 which avc observed in studying the tetanus curve (see Fig. 52). This " diminu- 



Fig. 66.— Record of changes in electric potential in a tetanized injured muscle of a frog. The leading- 

 off non-polarizable electrodes connected with the capillary electrometer touched the normal Longitud- 

 inal and injured cul surface of the muscle. The muscle was tetanized by an induction current applied 

 to its nerve, the rate of interruptions being 210 per second. A rise of tin- curve indicates an electrical 

 change of opposite direction t<> thai caused by the injury. The diminution of the current of injury, 

 which was less than in some oilier experiments, was onus volt. The time record at the bottom of the 

 curve was obtained from a tuning fork making 500 double vibrations perse id afb r Burdon San- 

 derson). 



tional effect" is only to be observed upon an injured muscle, since it repre- 

 sents a difference in potential between the normally contract ing and the injured, 

 imperfectly contracting muscle-substance. When all parts of the muscle are 

 normal and contracting to an equal amount, the electrical force- would be 

 everywhere of the same nature, balance one another, and give no external 

 evidence. Although the diminutional effect is only to be observed upon the 

 injured muscle, the temporary negative changes which follow each excitation 

 1 Journal of Physiology, 1895, vol. xviii. p. 717. 



