F. E. Nipher— Work done by a Muscle before exhaustion. 131 
comes zero, and the weight be simply held on the arm at a con- 
stant level, the arm very soon tires, showing that work is still 
done. This kind of work, which Prof. Haughton has called 
“statical” work, is purely molecular, and we hope to be able 
to show that it may be referred to and easily measured by the 
ey unit of mechanical work—the kilogram-meter. 
In the supposed case,* if the acceleration becomes negative, 
the time of fatigue increases, until for an acceleration of minus 
(g), the time required to wholly fatigue the arm is infinite. 
ese considerations show, not only the reality of ‘“statical” 
work, but also that it is an important element in all kinds of 
muscular work. 
s the unit of statical work, we shall adopt the work done 
by the horizontally outstretched arm in sustaining a weight of 
one kilogram for one second upon a lever-arm of one meter. 
his work is evidently equivalent to the lifting of this same 
weight through a certain height. 
_ As the unit of dynamical work, we shall take the dynam- 
teal work done by the horizontally outstretched arm, in lifting 
4 weight of one kilogram, through a height of one meter, with 
an acceleration of one meter per second, on a lever-arm of one 
meter. The solution of the problem evidently consists in find- 
Ing the relation between these two units. 
4 order to eliminate the fatigue caused by the downward- 
Punging weight, the apparatus shown in figs. 1 and 2 was de- 
vised. Bis a shelf armed with a plate of car-spring caoutch- 
th ¢, for the support of the weight. This shelf is fastened by 
© Iron bands I and a vertical back-piece V, to the slide U, 
bl Ing further supported by a cross-piece P. By usin suitable 
stare the dite may be raised to any desired height, which 
Deve 18 read off on a scale marked on the upright pieces A 
eg used as a support for the arm during the interval of rest, 
h . it can be adjusted to any desired height. S (fig. 2) is a 
rizontal string attached to the wire K, and to the wall of the 
cated, nPe Soon to be able to commence the veld of experiments here indi- 
. «Pparatus for which has been already devi 
t Hinrichs’ “School Laboratory.” 1871. p. 108. 
