322 F. FE. Nipher—Variation in the Strength of a Muscle. 
In this case, part of the work of the muscles consists in 
moving the hook of the dynamometer over a certain space. 2, 
under a constantly increasing strain P. The rest of the work 
done consists in sustaining the strain P, and the fatigue caused 
is due wholly to molecular motions in the muscle itself. Prof. 
Haughton has proposed to call the former work “dynamical,” 
the latter “ statical” work. 
The dynamical work D is then 
p=/1 P.de, or a8 Pc. 2 
(where ¢ is the tension of the dynamometer spring when z= 
2 
Dee =f cxde= +c" 
a i 
or between the limits z—0 and c= 
P2 
— rr 
In like manner the statical work S is 
D (1) 
S=—/Pdt oras P=c't 
where ¢’ is the value of P when ¢is unity— 
142 
s= =f c tdt=—— +0". 
or between the limits t—=0 and —s 
p2 
as th 2 
s=z (2) 
The value of D is measured in kilogram-meters; the value 
of S is measured in kilogram-seconds. It will be admitted 
that the statical work of holding a weight of w. kilos upon the 
out-stretched arm, is equivalent to the dynamical work of liftin 
w. kilos through a certain space. Calling the total work W; 
we shall have— 
W=D+4.8. (3) 
I propose to call & the dynamical equivalent of statical a 
No value has yet been obtained for it which can be deemed 
more than approximate. 
