14 Vol. XXXVII.. Art. 1.— K. Fuji : 



millimetre by means of verniers. AMieii in good ^\■orkiIlg-coIKli-^ 

 tion, the length of one millimetre on this a[)[)aratus corresponds 

 to 4-4x10"* sec. 



IV. Formula Expressing the Discharge Curve. 



From the oscillogram in Plate I., we see tliat the discharge 

 curve, caused by a direct stimulus, resembles the probability curve 

 of Gauss, except that it is not symmetrical with respect to the 

 maximum ordinate. After some assumptions, a formula is obtained 

 for expressing the curve that agrees very closely witli tlie experi- 

 mental curve. 



In the first })lacc it is assumed that tlie discharge of each 

 electric plate, caused by a single stimulus, is of \ery short duration. 

 It is a known fact that only the first small time-interval of a closing 

 current influences the height of the discharge curves, and this will 

 be discussed more fully afterwards. When this fact is considered, 

 it will not be unnatural to suppose, that a stimulus of sucli short du- 

 ration causes a discharge of an instantaneous nature. In the second 

 place it is assumed that the interval between the stimulus and the 

 discharge of a single plate in response to it, which interxal may be 

 called the latent period of a single plate, may have various values, and 

 among them there is a certain value, which predominates in 

 number, so that other values deviate more or less from it according 

 to the law of errors, though in a somewhat modified form. This 

 predominating latent period may be called the modal latent period, 

 which, as will be explained afterwards, represents the interval be- 

 tween the stimulus and the instant corresponding to the maximum 

 point of the discharge curve. In biological phenomena there exist 

 many instances which are governed by a law that involves the idea 

 of probability. The phenomenon of contingency and of correlation 

 treated by Pearson and others are such examples. Here it is 

 simply assumed that a similar relation exists in the quantity — the 

 latent period of a single plate. 



In Gauss's probability curve, the freedom of deviation from 

 its most probable value is symmetrical with respect to it. In the 



