91 



It is probable that the muscles here given as rotators never act together 

 in one leg only, for the Lion never attempts to stand on one leg ; but 

 it may be useful to calculate what would be the direction and magnitude 

 of their total resultant. Assuming the plane of the component couple 

 Xto be that of the muscles obturator extemus and adductor magnus, we 

 find— 



X = 16 -22 + 0 -75 cos 60° - 0 *53 cos 31° - 17 cos 13° - 6 cos 86° 



+ 10-5 cos 83°= 0'29 oz. 



F= 0 + 0-75 sin 60° + 0*53 sin 31°- 12 sin 13°- 6 sin 86° 



- 10-5 sin 83° = - 18-18 oz. 



^ = - tan (89 c 5') 

 X 



yr*TX2=: 18*18 OZ. 



The resultant moment of all the muscles causing rotation lies, therefore, 

 in a plane nearly perpendicular to the plane of the obturator extemus, 

 and is represented by a weight of lion flesh of 18*18 oz. acting towards 

 the body. 



When the Lion crouches on his haunches, with his feet somewhat 

 apart, and knees approximated, acting as fulcra, the origins and inser- 

 tions of the rotator muscles are converted, and they all become avail- 

 able to assist in his spring, which is thus aided by the propulsion of the 

 haunch upwards by the joint action of the rotator muscles of both legs ; 

 and his body is at the same time propelled forward by the action of all 

 the extensors of the thigh, leg, and foot of both sides. 



Paet III. — Muscles of Should ee and Elbow Joints. 



1. M. pectoralis major, 34* oz. 



Origin, from whole length of sternum. 



Insertion, into whole length of pectoral ridge of humerus, with a 

 slip joining the deltoido-trapezius as it passes on to be inserted in 

 the radius. 



2. M. pectoralis minor, 7f oz. 



3. M. deltoido-trapezius, 15 J oz. 



This conjoined muscle forms a large sheet, covering the scapula 

 and head of humerus, and flowing freely over them in the rapid 

 actions of the arm; it is inserted partly into the moveable 

 clavicle, and partly into the inner side of the ulna, one inch 



below the elbow joint. 



4. M. deltoideus proprius, 4 j oz. 



Origin, anterior third of spine of scapula. 

 Insertion, deltoid ridge on outer side of humerus. 



5. M. cleido-mastoideus, 4| oz. 



This muscle has a double origin, from the mastoid process and from 

 the transverse process of the dentatus ; it is inserted into the float- 

 ing clavicle. 



