Rev. S. Haughton on Animal Mechanics. 295 



1. Biceps femoris (long head) . . . 2'59 sq. in. 



„ (short head) . . . 1-14 „ 



2. Semitendinosus 1\S7 „ 



3. Semimembranosus 225 ,, 



4. Gracilis 0-89 „ 



5. Sartorius 059 „ 



^^ 



When the arm was held vertically, and the forearm horizontally 

 with the fist shut and in supination, I found that 39 lbs. was the 

 limit of the weight that could be lifted when suspended at 12| 

 inches from the axis of the elbow-joint, and that tlie perpendi- 

 culars let fall upon the directions of the muscles from the same 

 axis were : — 



1. Biceps humeri 2"0G inches. 



2. BracliicBus 1'07 „ 



Hence if K denote the force of the muscle, per square inch of 

 cross section, we have, adding 2 lbs. for the weight of the forearm 

 at \1\ inches from the axis of the joint, 



41 lbs. X 12i inches=K x \ x^^^ ^ j^.gy 



502|=Kx 1^ 



= Kx 5-304 

 and finally K= 947 lbs. 



•935 1 

 •369 J 



This represents the force per square inch of cross section that 

 the muscles flexing the forearm are capable of exerting. 



In order to measure the force of the muscles flexing the leg, I 

 placed the observer lying upon his face upon a table, with the 

 legs extended over its edge, and having fastened down the 

 thighs, I observed the maximum weights, suspended from the 

 heel that could be conveniently lifted, and found that 34 lbs. was 

 the limit ; to this must be added 3 lbs. for the weight of the leg, 

 supposed suspended at the heel, which was measured as 16| 

 inches from the axis of rotation of the knee-joint. The perpen- 

 diculars let fall upon the directions of the several muscles flexing 

 the leg were then measured : — 



Perpendicular. 



1. Biceps femoris (long head) .... 0'95 in. 



„ (short head) .... 0"56 „ 



2. Semitendinosus 0"40 „ 



3. Semimembranosus 0'65 „ 



4. Gracilis 0*25 „ 



5. Sartorius O'OO „ 



Hence we find, for the determination of K (the coefficient of 

 muscular contraction per square inch of cross section), 



