NEGATIVE VARIATION 



799 



affected by the excitation, and therefore undergoing a smaller negative 

 change than the uninjured, becomes relatively to the latter less nega- 

 tive. Appearing as a diminution or reversal of the current of rest, it was 

 called the negative variation. The term negative is not used here in 

 its electrical, but in its algebraic, sense, and merely as indicating the 

 direction of the current with reference to that of the demarcation 

 current. It is in this sense that ' negative variation ' and the converse 

 term, 'positive variation,' are used (pp. 810, 811 )in speaking of the 

 electrical changes produced in glands and in the retina by stimulation. 



A. B. 



Fig. 287. ' Spike ' (Diphasic Variation) of Uninjured 

 Gastrocnemius (Sanderson). 



A photographed on slow, B on fast-moving, plate. 



Fig. 288. Variation of In- 

 jured Gastrocnemius (San- 

 derson). A 'spike' fol- 

 lowed by a ' hump.' 



Fig. 289. Variation of Injured Gas- 

 trocnemius (Sanderson). The plate 

 was moving ten times faster than in 

 Fig. 288. 



Fig. 290. Variation of Uninjured 

 Muscle excited Eighty- Four Times 

 a Second (Sanderson). 



Fjg 291. Curve of an Injured Muscle excited Sixty Times a Second (Sanderson). 



