11. Body
a. Breast. The breast (or chest) is broad and full in front; depth of breastbone should not exceed the width.
b. Shoulders. The shoulders are heavy and strongly reinforced with muscles.
c. Back. The back is well-feathered, strong, flat and broad at the shoulders, narrowing toward the rump.
Figure 1. Parts of homing pigeon.
d. Keel. The keel is strong, arched in front, and of medium length and depth. Width of keel denotes strength.
e. Abdomen. The abdomen is reduced to the smallest proportions.
f. Wings. The wings must be medium-sized, strong, well-proportioned, and rounded at the butt, with plenty of muscle. Primary flights should be of a good width, with plenty of overlapping space and a pronounced curvature towards the body. See [i] below. Secondary feathers should also be long and wide to provide a good covering for the entire back. Covert feathers should be sturdy and abundant, because they supply additional wing strength, as well as protect pigeons against adverse weather.
g. Pelvic bones. The pelvic bones (or vent bones) are very firm, close together over the vent, and extend toward the keel on each side of the vent. These bones form a body girdle by which the legs are joined to the body.
h. Rump. The rump is wide and continues the line of the back. It is well covered on all sides with fine, soft feathers.
i. Tail feathers. The tail feathers, 12 in number, are short, wide, overlapping, and do not extend farther than ¾ inch beyond the wing tips.
j. Legs. The legs are of medium length and well muscled. Thighs are chubby. Lower leg is red and stout, and toes are short with firm nails.
12. Respiratory Channels ([fig. 2])
Figure 2. Respiratory channels of homing pigeon. (Air sacs are named in accordance with McLeod and Wagers. Other names are given in parenthesis.)
Respiratory channels are highly developed, enabling the pigeon to fly continuously from 12 to 15 hours. Air circulates through the bronchial tubes and lungs and also through nine air sacs, from which other small, irregular cavities extend under the skin between the muscles, and even into the inside of the bones. These small air sacs contain a reserve of warm air which feeds the lungs during flight when the muscular apparatus consumes a large amount of oxygen. They inflate and collapse alternately, acting as a lift and force pump which renews air in the lungs.