ANIMAL MECHANICS. 



177 



force of the biceps, and the velocity of motion produced by it, 

 as compared with the brachiceus ; and the angle through 

 which it bends the forearm is only one-fifth the angle of 

 flexion due to the brachiceus; while in the Lioness these 

 angles are nearly equal, and in Man the angular motion 

 caused by the biceps is greater than that produced by the 

 brachiceus. 



These peculiarities are common to the Ass and Horse 

 in which latter animal the " gig action" of the fore foot, so, 

 much admired, is altogether due to the same cause as in the 

 Ass, viz., the rapid flexion of the elbow joint caused by the 

 pennate arrangement of the fibres of the biceps muscle, pro- 

 ducing a powerful contraction through a short space. 



The mylohyoid muscle, which forms the floor of the mouth 

 {diaphragma oris), is another good example of the penniform 

 arrangement of muscular fibres. This muscle, as it exists in 

 Man, is shown in Fig. 27, where H denotes the hyoid bone, 



Fig. 27. 



and S the symphysis. The posterior fibres of the muscle are 

 attached directly to the tongue bone, while the anterior fibres 

 N 



