Chap. VII. 



THE EFFECTS OF DISUSE. 



285 



Burmese Jumper, which has unnaturally short legs, are slightly 

 shortened relatively to the leg-bones ; but the decrease is so slight 

 that it may be due to the standard specimen of G. bankiva having 

 accidentally had wings of slightly greater length than usual ; so 

 that the measurements are not worth giving. But it deserves 

 notice that the Silk and Frizzled fowls, which are quite incapable 

 of flight, had their wings less reduced relatively to their legs than 

 in almost any other breed ! We have seen with domesticated 

 pigeons that the bones of the wings are somewhat reduced in length, 

 whilst the primary feathers are rather increased in length, and it is 

 just possible, though not probable, that in the Silk and Frizzled 

 fowls any tendency to decrease in the length of the wing-bones from 

 disuse may have been checked through the law of compensation, by 

 the decreased growth of the wing-feathers, and consequent increased 

 supply of nutriment. The wing-bones, however, m both these breeds, 

 are found to be slightly reduced in length when judged by the 

 standard of the length of the sternum or head, relatively to these 

 same parts in G. bankiva. 



The actual weight of the main bones of the leg and wing in twelve 

 breeds is given in the two first columns in the following table. The 

 calculated weight of the wing-bones relatively to the leg-bones, in 

 comparison with the leg and wing-bones of G. bankiva, are given 

 in the third column, — the weight of the wing-bones in G. bankiva 

 being called a hundred. 73 



Table I. 



73 It may be well to explain how 

 the calculation has been made for the 

 third column. In G. bankiva the 



leg -^ones are to the wing-bones as 

 86 : 54, or as (neglecting decimals) 

 100 : 62; — in Cochins as 311 : 162, or 



