362 CHORDATA. 
The smaller feathers are called coverts and contour 
feathers, according to their size and structure. The /i- 
plumes are still smaller feathers, resembling hairs, with a 
thin shaft terminating in a very small vane. They can be 
seen still attached to the skin after plucking. The scales 
on the legs and claws are epidermic and closely similar to 
those found in the reptiles. 
After plucking, the skin may be removed from the 
ventral surface by a median incision from head to cloacal 
aperture (see Plate VIII.). The greater part of the body 
Fig. 257.—VIEW OF RESPIRATORY ORGANS OF THE 
Pigeon. (Slightly Diagrammatic.) 
Trachea. 
Clavicular-Sac. 
Syrinx. 
Bronchus. 
Opening of 
Bronchus into 
Air-Sac, 
Opening of 
Bronchus into 
Posterior 
Air-Sac. 
_ Anterior 
Abdominal. 
--—— Posterior 
Abdominal. 
The median sac is the interclavicular. - 
is seen to be occupied by the “ breast,” a mass of muscles 
lying on the large sternum. The central ee? (or carina) 
of the sternum may be seen in the middle line. The 
pectoral muscle can be cut away from its point of origin 
along the sternum and clavicle, and thence forward. It 
is inserted into the large deltoid ridge of the humerus. 
It is evident that on contraction this muscle will depress 
the wing. Under it lies the swdclavian muscle, originating 
from the sternum and passing upwards by a tendon which 
can be followed through a foramen in the shoulder-girdle, 
called the foramen triosseum, on to the upper side of the 
