In the sternum, furculum, coracoids, and scapulae, the differences are so slight and so variable as not to be worth notice, except that in two skeletons of the Penguin duck the terminal portion of the scapula was much attenuated.
In the bones of the leg and wing no modification in shape could be observed. But in the Penguin and Hook-billed ducks, the terminal phalanges of the wing are a little shortened. In the former, the femur, and metatarsus (but not the tibia) are considerably lengthened, relatively to the same bones in the wild duck, and to the wing-bones in both birds. This elongation of the leg-bones could be seen whilst the bird was alive, and is no doubt connected with its peculiar upright manner of walking. In a large Aylesbury duck, on the other hand, the tibia was the only bone of the leg which relatively to the other bones was slightly lengthened.
ON THE EFFECTS OF THE INCREASED AND DECREASED USE OF THE LIMBS.
In all the breeds the bones of the wing (measured separately after having been cleaned) relatively to those of the leg have become slightly shortened, in comparison with the same bones in the wild duck, as may be seen in Table 8.I.
TABLE 8.I.a.
COLUMN 1. Length of Femur, Tibia, and Metatarsus together (inches).
COLUMN 2. Length of Humerus, Radius, and Metacarpus together (inches).
COLUMN 3. Or as (ratio).
Name of Breed. 1. 2. 3.
Wild mallard. 7.14 9.28 100:129 Aylesbury. 8.64 10.43 100:120 Tufted (Dutch). 8.25 9.83 100:119 Penguin. 7.12 8.78 100:123 Call. 6.20 7.77 100:125
TABLE 8.I.b.
COLUMN 1. Length of Femur, Tibia, and Metatarsus together (inches).
COLUMN 2. Length of all the bones of the wing (inches).
COLUMN 3. Or as (ratio).
Name of Breed. 1. 2. 3.
Wild duck (another specimen). 6.85 10.07 100:147 Common domestic duck. 8.15 11.26 100:138
In table 8.I we see, by comparison with the wild duck, that the reduction in the length of the bones of the wing, relatively to those of the legs, though slight, is universal. The reduction is least in the Call duck, which has the power and the habit of frequently flying.
In weight there is a greater relative difference between the bones of the leg and wing, as may be seen in Table 8.II:
TABLE 8.II.a.
COLUMN 1. Weight of Femur, Tibia, and Metatarsus (grains).
COLUMN 2. Weight of Humerus, Radius, and Metacarpus (grains).
COLUMN 3. Or as (ratio).
Name of Breed. 1. 2. 3.
Wild mallard. 54 97 100:179 Aylesbury. 164 204 100:124 Hooked-bill. 107 160 100:149 Tufted (Dutch). 111 148 100:133 Penguin. 75 90.5 100:120 Labrador. 141 165 100:117 Call. 57 93 100:163
TABLE 8.II.b.
COLUMN 1. Weight of all the Bones of the Leg and Foot (grains).
COLUMN 2. Weight of all the Bones of the Wing (grains).
COLUMN 3. Or as (ratio).
Name of Breed. 1. 2. 3.
Wild (another specimen). 66 115 100:173 Common domestic duck. 127 158 100:124
In these domesticated birds, the considerably lessened weight of the bones of the wing (i.e. on an average, twenty-five per cent of their proper proportional weight), as well as their slightly lessened length, relatively to the leg-bones, might follow, not from any actual decrease in the wing- bones, but from the increased weight and length of the bones of the legs.
TABLE 8.III.a.
COLUMN 1. Weight of entire Skeleton (grains). (N.B. One Metatarsus and Foot was removed from each skeleton, as it had been accidentally lost in two cases.)
COLUMN 2. Weight of Femur, Tibia, and Metatarsus (grains).
COLUMN 3.