376 



DR. PETTIGREW ON THE PHYSIOLOGY OF WINGS. 



of the bird's wing have each what is equivalent to a long and a short axis. Thus 

 the primary and secondary feathers marked h ij, k I are capable of rotating on 

 their long axes (r s) and upon their short axes (m n). The feathers rotate upon 



, c 



their long axes in a direction from below upwards during the down stroke, to 

 make the wing impervious to air ; and from above downwards during the up 

 stroke, to enable the air to pass through it. The primary, secondary, and 

 tertiary feathers have thus a distinctly valvular action.""" They rotate upon their 

 short axes (m n) during the descent and ascent of the wing, the tips of the feathers 

 rising slightly during the descent of the pinion and falling during its ascent. 



The Primary, Secondary, and Tertiary Feathers are Geared to each other, 

 and Act in Concert. — To admit of the primary, secondary, and tertiary feathers 

 rotating upon their long axes (r s), a very elaborate combination of fibrous and 

 elastic structures, with a certain admixture of muscular substance, is necessary. 

 The arrangement, as witnessed in the crested crane, is given at Plate XVI. 

 figures 24, 25, 26, 27, and 28. 



The roots of the primary, secondary, and tertiary feathers are imbedded 

 behind the muscular mass (/, /, h), fig. 24, Plate XVI. The insertions of the 

 roots of the feathers are shown in figure 28, Plate XVI. Each root is enveloped 

 by a continuous elastic ligament {op q of fig. 24), this ligament being provided 

 with fibrous bands, which run in the direction of the length of the wing (/• s, t u, 

 vw of figs. 25 and 27, Plate XVI.) and obliquely (g h, g h). Two oblique bands {g 

 and h) run between every two feathers (<#), and are joined to the longitudinal ones 

 (rs tu vw), and to the feathers in such a manner that the whole are geared 

 together, an arrangement combining great freedom of movement with great 

 strength. The longitudinal bands run along the roots of all the feathers, and 



The valve action, as explained, is called more or less into play according to circumstances. 



