S. Haughton—Mechanical Work done by a Muscle. 185 
out, wid ers not; whereas the “ Law of Fatigue” Cam 
: all cases there — nae all marked stages : 
. The work done with ease. 
2 Accompanied by pane distress. 
3. Accompanied by pain in the muscles used. 
ee the last stage, great care must be taken to prevent 
chang the posture and mode of motion, by which ad- 
ditional muscular fibers may come in aid of the fibers nearly 
atigue 
Let W denote the total work done, and T the time of doing 
it; then, by the “ Law of Fatigue,” 
ad 
r= constant. (1) 
If w be the weight held in the hand and a be half the weight 
of the arm, and 2 the number of times the ee are lifted: 
Since the ‘tine of raising and lowering the arms is constant, n 
is proportional to T, and the “Law of Fatigue” ie us the 
formul 
(wa)in=A, (2) 
where A is an unknown constant. 
In the following table I give the values of w and the mean 
value of n for 20 distinct persons. 
The time of lift is in all cases one second, 
TABLE I.—MEAN OF TWENTY EXPERIMENTERS. 
No. w. n (obs.) n (cale.) Diff. 
1 2°50 lbs. 131°80 128°0 8 
4 4°25 87°55 783 +9°2 
3 a7 47°35 §3°5 —6°2 
4 gy grees 40°25 43°7 —3°5 
5 Ce 34°60 37°71 —2°5 
6 15.2 27°15 26°8 +0°3 
7 14°00 “ 17°20 15°4 +1°8 
The column containing the calculated atone of n was ob- 
tained from equation (2) by using the value 
a==3°50 Ibs. 
A=4699 “ 
