84 THE FLIGHT OF BIRDS 
the wing is bent the muscle lies in a slightly curved 
form—we notice it When we are getting the meat 
from between the two long bones of a chicken’s 
wing. It is straightened out when the wing 
straightens, and this, combined with the outward 
slope assumed by the feathers as they spread, 
stretches the little tendons that arise from it and 
are fastened to the feathers. The tendons slope 
outward, away from the shoulder, and attach to 
the under-side of the quills, or rather to the 
fibrous tissue with which the quills are surrounded. 
M. Alix (in his Appareil locomoteurdes Oiseaux) makes 
some of them at any rate attach to the further edge 
of the lower face of the quills, and gives them the 
. eredit for rotating the feathers during the down- 
stroke, so that they press against one another and 
make the wing impervious to air. But when I have 
scraped these little tendons away in the wing of a 
freshly-killed Pigeon I have found that, when I 
extended the wing, the feathers still took their 
proper position. The extending of the wing causes a 
stretching of all the important stays—the ligaments, 
the sheet of fibrous tissue, and these tendons—and 
the ligaments may claim the largest share of the 
credit for the spreading and marshalling of the 
feathers. During the up-stroke the secondaries 
are firmly tethered, but are no longer marshalled 
for action. There are interspaces as there are 
between the leaves of a folded fan that has seen 
much service. The feathers being now no longer 
pressed tight together, the air can pass between 
them. When, however, the bird is flying fast and 
the wings are lifted, not so much by muscles 
