128 ELECTRO-PHYSIOLOGY CHAP. 



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law, the muscles of the toad do not, arid it applies even less to 

 the more sluggish contractile tissues (smooth muscle, many 

 Protozoa, etc.). " Since in these, from their sluggishness, a given 

 physiological state is more than usually prolonged, they are 

 especially adapted for stimuli of long duration and gradual onset." 

 To borrow a comparison from Griitzner (14, p. 384), it is with 

 these as with the movement of heavy sluggish masses impelled 

 by external momentum. " If we shoot a bullet against a large 

 heavy wooden door, turning easily on its hinges, the ball passes 

 through, without pushing the door on the hinge. But if the 

 same amount of energy as is contained in the moving bullet is 

 directed against the door by increasing the mass of the ball while 

 its velocity is diminished, then such a ball will readily turn the 

 door on its hinges. Thus an induction shock of abrupt onset 

 injures a sluggish (smooth) muscle without causing contraction, 

 while the same quantity of electricity distributed over a longer 

 period may excite a vigorous twitch, without injury." Slow 

 moving stimuli are thus, according to Griitzner, the adequate 

 incitation for slowly developing processes. 



The different physiological action of the make and break 

 induction shock again appears to rest, not solely upon differences 

 of time-distribution, but also upon the still obscure dissimilarity 

 of electrolytic effects. Griitzner (14) found that currents of 

 abrupt onset, including break induction currents, have a much 

 stronger electrolytic action than those which commence more 

 gradually. This would account for the fact that, in direct excita- 

 tion of homogeneous striated or even smooth muscle (e.g. the 

 adductor muscle of the shell of Anodonta), the contraction dis- 

 charged by a break shock is usually the most conspicuous, i.e. 

 makes its appearance earlier. 



These facts lead us to anticipate that the form of the curve 

 of oscillation of an electrical current is not without effect upon 

 the excitatory action ; and the first essential for determining this 

 point is that we should be able at will to modify and vary the 

 nature of the increase of intensity (or density) in a battery 

 current. The problem of raising a galvanic current in a circuit 

 from zero, by different degrees, to a certain final value, was first 

 attacked by v. Fleischl (15). 



He succeeded by means of his " orthorheonome " in producing 

 increment and decrement of the exciting current at any uniform 



