64 



ANIMAL MECHANICS. 



ject, in which the distance from the axis of the elbow joint to 

 the ungual articulation of the middle finger was the same as 

 in my own arm, viz. 16.55 in., and found as follows : — 



1 . Perpendicular on Biceps humeri, 2.06 in. 



2. Perpendicular on Brachiceus, . 1.07 „ 



Hence, if K denote the coefficient of muscular force, per 

 square inch of cross section, we have 



The moment of the muscles = K (1.91 x 2.06 + 1.28 x 1.07) 

 = 5.304 xK; 



and, equating this to the moment of force applied, we obtain 

 5°*i = 5-3°4 x K> 



and, 



K= 94.7 lbs. per sq. in. = 6.658 Kilos, per sq. cent. 



Considering that the arm examined after death was that 

 of a blacksmith, it is possible that I have somewhat over- 

 estimated the cross section of the muscles, as compared with 

 my own ; but, on the other hand, it must be remembered, as 

 I have shown in pp. 45, 6, that a large percentage should be 

 added to dead muscles, in order to bring them up to the 

 standard of life. 



Other writers, especi^Jly Donders and Mansfelt, have 

 given measures of the lengths and cross sections of the biceps 

 and brachiceus, which I have added in a note,* partly on account 



* Over de Elasticiteit der Spieren. Utrecht, 1863. 



Av. of Eight. One. 



1 . Distance from axis of elbow to insertion of biceps, . 39m.n1. 45m.n1. 



2. Length of fibres of long bead, 158 160 



3. Length of fibres of short head, 202 204 



4. Length of the whole long head, 388 400 



5. Length of the whole short head, 355 366 



6. Distance from axis of elbow to middle of insertion of 



brachiaeus, . . . 32 30 



7. Length of fibres of brachiceus, (51-143) (48-134) 



8. Length of whole brachiaeus, 237 



