ANIMAL MECHANICS. 



249 



From this it appears that the two groups of muscles are 

 nearly of equal weights, and therefore contain nearly equal 

 quantities of work stored up ; so that their simultaneous 

 action is highly advantageous. It may be noticed that in the 

 case of a ginglymoid joint, like the elbow, where the motion 

 of the bone is circular, the condition required by Proposition B. 

 is necessarily fulfilled in every position of the bone. 



(b). Latissimus dor si of the Tiger and Lion. —The position 

 and relations of the latissimus dorsi in the Tiger are shown 

 in Fig. 6;, where Sis the centre of the glenoid cavity, C is 



Fig. 65. 



the centre of motion of the elbow joint, and Q is the position 

 of the centre of the tendon of the latissimus dorsi, inserted on 

 the inner side of the humerus. The line, QA, drawn to the 

 fifth dorsal vertebra, represents the anterior fibres of the 

 muscle, and QB, drawn to the third lumbar vertebra, repre- 

 sents its posterior fibres. The line, QX, bisecting the angle, 



