(7/74. Mr. Blyth (in 'Annals and Mag. of Nat. Hist.' 2nd series volume 1 1848 page 456) gives 3 1/4 pounds as the weight of a full-grown male G. bankiva; but from what I have seen of the skins and skeletons of various breeds, I cannot believe that my two specimens of G. bankiva could have weighed so much.) I am indeed inclined to suspect that the leg-bones in the Dorking, No. 2 in the table, are proportionally too heavy; but this bird was a very large one, weighing 7 pounds 2 ounces, though very thin. Its leg-bones were more than ten times as heavy as those of the Burmese Jumper! I tried to ascertain the length both of the leg-bones and wing-bones relatively to other parts of the body and skeleton: but the whole organisation in these birds, which have been so long domesticated, has become so variable, that no certain conclusions could be reached. For instance, the legs of the above Dorking cock were nearly three-quarters of an inch too short relatively to the length of the sternum, and more than three-quarters of an inch too long relatively to the length of the skull, in comparison with these same parts in G. bankiva.
TABLE 7.II.
COLUMN 1. Length of Sternum (in inches and decimals.)
COLUMN 2. Depth of Crest of Sternum (in inches and decimals.).
COLUMN 3. Depth of Crest relatively to the length of the Sternum, in comparison with Gallus bankiva.
1. 2. 3.
Gallus bankiva -- male. 4.20 1.40 100
1. Cochin -- male. 5.83 1.55 78 2. Dorking -- male. 6.95 1.97 84 3. Spanish -- male. 6.10 1.83 90 4. Polish -- male. 5.07 1.50 87 5. Game -- male. 5.55 1.55 81 6. Malay -- female. 5.10 1.50 87 7. Sultan -- male. 4.47 1.36 90 8. Frizzled hen -- male. 4.25 1.20 84 9. Burmese Jumper -- female. 3.06 0.85 81 10. Hamburgh -- male. 5.08 1.40 81 11. Hamburgh -- female. 4.55 1.26 81 12. Silk fowl -- female. 4.49 1.01 66
In Table 7.II. in the two first columns we see in inches and decimals the length of the sternum, and the extreme depth of its crest to which the pectoral muscles are attached. In the third column we have the calculated depth of the crest, relatively to the length of the sternum, in comparison with these same parts in G. bankiva. (7/75. The third column is calculated on the same principle as explained in footnote 7/73 above.)
By looking to the third column we see that in every case the depth of the crest relatively to the length of the sternum, in comparison with G. bankiva, is diminished, generally between 10 and 20 per cent. But the degree of reduction varies much, partly in consequence of the frequently deformed state of the sternum. In the Silk fowl, which cannot fly, the crest is 34 per cent less deep than what it ought to have been. This reduction of the crest in all the breeds probably accounts for the great variability, before referred to, in the curvature of the furculum, and in the shape of its sternal extremity. Medical men believe that the abnormal form of the spine so commonly observed in women of the higher ranks results from the attached muscles not being fully exercised. So it is with our domestic fowls, for they use their pectoral muscles but little, and, out of twenty-five sternums examined by me, three alone were perfectly symmetrical, ten were moderately crooked, and twelve were deformed to an extreme degree. Mr. Romanes, however, believes that the malformation is due to fowls whilst young resting their sternums on the sticks on which they roost.]
Finally, we may conclude with respect to the various breeds of the fowl, that the main bones of the wing have probably been shortened in a very slight degree; that they have certainly become lighter relatively to the leg-bones in all the breeds in which these latter bones are not unnaturally short or delicate; and that the crest of the sternum, to which the pectoral muscles are attached, has invariably become less prominent, the whole sternum being also extremely liable to deformity.