i 



Chap. VIII. 



EFFECTS OF USE AND DISUSE. 



285 



In the foregoing table we see that, in comparison with the wild duck, 

 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 the following table : — 



Name of Breed. 



Weight of Femur, 

 Tibia, and 

 Metatarsus. 



Weight of 

 Humerus, Radius, 

 and Metacarpus. 



Or as 



Wild mallard 



Hooked-bill 



Tufted (Dutch) 



Call 



Grains. 



54 

 164 

 107 

 111 



75 

 141 



57 



Grains. 



97 

 204 

 160 

 148 



90-5 

 . 165 



93 



100 : 179 

 100 : 124 

 100 : 149 

 100 : 133 

 100 : 120 

 100 : 117 

 100 : 163 



Wild (another specimen) 

 Common domestic duck 



Weight of all the 

 Bones of the 

 Leg and foot. 



Weight of all the 



Bones of the 



Wing. 



100 : 173 

 100 : 124 



Grains. 



66 

 127 



Grains. 

 115 

 158 



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. The first of the two tables on the next page shows that the leg- 

 bones relatively to the weight of the entire skeleton have really increased in 

 weight; but the second table shows that according to the same standard 

 the wing-bones have also really decreased in weight ; so that the relative 

 disproportion shown in the foregoing tables between the wing and leg 

 bones, in comparison with those of the wild duck, is partly due to the 

 increase in weight and length of the leg-bones, and partly to the decrease 

 in weight and length of the wing-bones. 



With respect to the two following tables, I may first state that I tested 

 them by taking another skeleton of a wild duck and of a common domestic 

 duck, and by comparing the weight of all the bones of the leg with all those 

 of the wings, and the result was the same. In the first of these tables we 

 see that the leg-bones in each case have increased in actual weight It 

 might have been expected that, with the increased or decreased weight 

 of the entire skeleton, the leg-bones would have become proportionally 

 heavier or lighter; but their greater weight in all the breeds relatively 

 to the other bones can be accounted for only by these domestic birds 

 having used their legs in walking and standing much more than the wild, 

 for they never fly, and the more artificial breeds rarely swim. In the second 



