3°° 



ANIMAL MOVEMENT 



weighty organs must be accumulated in the body. To speak 

 metaphorically, the wings must be made up of very little besides 

 masts, sails, and cordage." 



The two largest muscles concerned with flight are those which 

 make up the great fleshy mass of the breast, and of which the use 

 is to lower and raise the wings (see fig. 834). By far the bigger 

 of the two is the great breast muscle i^pectoralis vtajor), which 

 is attached to the lower side of the humerus not far from the 

 shoulder-joint, and by its contraction pulls down the wing. 



^ Qui II 



Fig. 834, — Strnctiire of Pheasant's Wing 



H, Humerus; R, radius; B.w., bastard-wing; F.\v-i\i. and h.\v-m., front and hind wing-membranes; 

 St. I and St. 2, straightening muscles ; b. i and e. 2, bending muscles ; T. i, t. 2, and T. 3, tensor 

 muscles; Pect., part of great breast-muscle [pectoralis major). 



It covers the smaller elevator muscle {s^ibclavhts), of which the 

 work is to raise the wing. But being below this, its tendon 

 has to take a rather curious course. It runs through a hole 

 situated where the three bones of the shoulder meet, and then 

 bends down to be attached to the upper side of the humerus 

 not far from the shoulder-joint. We may compare it to a rope 

 that passes over a pulley. Some other important muscles are 

 shown in fig. 834. Among them may be mentioned: — (i) Muscles 

 which straighten out the forearm on the upper-arm (St. i), and 

 the hand on the forearm (St. 2); (2) Muscles which bend the 

 forearm on the upper-arm (B.i.), and the hand on the forearm 

 (B.2.); (3) Tensor muscles (T. i, T.2, T. 3), which keep the 



