20 



The Rev. S. Haughton on some Elementary [June 20^ 



the fore arm, I found the cross sections of the Biceps humeri and Bra- 

 cMceus to be as follows : — 



Cross section. 



1. Biceps humeri l'914i sq. in. 



2. Bracliiceus 1'276 „ 



3-190 



The cross sections of the muscles that bend the leg were found to be 

 in the same subject — 



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



„ (short head) 1*14 „ 



2. Semitendinosiis 1*87 „ 



3. Semimemlranoszis 2'25 „ 



4. Gracilis 0*89 „ 



5. Sartoriits 0'59 „ 



9-33 



"When the arm was held vertically, and the fore arm horizontallj, 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 the perpendiculars let fall upon the direc- 

 tions of the muscles from the same axis were — 



1. Biceps hwneri 2'06 inches. 



2. BracJiiceus 107 „ 



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

 section, we have, adding 21bs. for the weight of the fore arm at 12| inches 

 from the axis of the joint, 



=Kx 5-304 



and finally K= 947 lbs. 



This represents the force per square inch of cross section that the 

 muscles flexing the fore arm 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 

 perpendiculars let fall upon the directions of the several muscles flexing 

 the leg were then measured : — 



