396 DR PETTIGREW ON THE PHYSIOLOGY OF WINGS. 



by the falling forward of the body, by the reaction of the air, and by the con- 

 traction of the elastic ligaments. The air and the elastic ligaments contribute 

 to the elevation of the wing, but both are obviously under control — they, in 

 fact, form links in a chain of motion which at once begins and terminates in 

 the muscular system. 



That the elastic ligaments are subsidiary and to a certain extent under the 

 control of the muscular system in the same sense that the air is, is evident from 

 the fact that voluntary muscular fibres run into the ligaments in question at 

 various points. Thus, in the pheasant, as shown at a b of figure 23, Plate XV., 

 red muscular fibres are seen terminating in the fibrous and elastic tissues 

 c and k. These structures act in conjunction, and fold or flex the forearm on 

 the arm. At / h voluntary muscle is seen acting in concert with the elastic 

 ligament g i to flex the hand upon the forearm. The arm is drawn towards 

 the body by the elastic ligament d and by the muscles v w. 



The elastic ligaments, while occupying a similar position in the wings of all 

 birds, are variously constructed in the several species. In the common snij)e, 

 for example, as represented at figure 21, Plate XV., the voluntary muscular 

 slip a terminates in the fibro-elastic band k ; this again being geared to volun- 

 tary muscle x, and to certain musculo-fibrous bands j. Their conjoined action 

 is to flex the forearm upon the arm, the arm being drawn towards the body by 

 a musculo-fibrous ligament d, e. The elastic ligament g i flexes the hand upon 

 the forearm, and the ligament r the fingers upon the hand. A somewhat 

 similar arrangement is formed in the wing of the crested crane, as shown at 

 figure 24, Plate XVI. Thus, at a, b, voluntary muscular slips are seen termi- 

 nating in the elastic band k, this splitting up into two portions at k, m. A some- 

 what similar band is seen at/, and all three are united to, and act in conjunc- 

 tion with, the great fibro-elastic web c to flex the elbow. The musculo-fibro- 

 elastic ligament / g, li i, as already explained, envelopes the root of each 

 primary, secondary, and tertiary feather. It also forms a symmetrical network, 

 so that it at once supports the feathers and limits their peculiar actions. In 

 the swan the muscular slip which corresponds to a of figure 24, Plate XVI. 

 (crested crane), terminates in a fibrous band, which corresponds to k; but the 

 muscular slip corresponding to b terminates in a well-defined tendon, not in the 

 fibrous band m, but in a distinct muscle, 5 inches in length and \ of an inch 

 in breadth. This muscle is situated in the anterior margin of the wing, mid- 

 way between the shoulder and wrist joints, and exercises a most potent influence 

 in folding the elbow. The band marked / in the crane's wing is at least four 

 times broader in the swan's wing. 



The Elastic Ligaments more Highly Differentiated in Wings which Vibrate 

 Rapidly. — From what has been stated, it will be evident that the elastic liga- 

 ments of the swan are more complicated and more liberally supplied with 



