. The structure and life of birds . | Bones very little or not at all of humerus. Logger-headed Duck . Scoter Duck Nestor Parrot Red-throated Diver .Spur-winged Goose . l3 TS a 4 I These measurements speak for themselves, evenwithout any exact statement of the weights of thebirds ; but the following illustration will do more toexplain the problem of hollow bones. The shoulderbones of a Skua Gull, which has scarcely any aeration,of a vociferous Sea Eagle, and a Hornbill, both of whichare highly pneumatic, are placed side by side. The VI FORM AND FUNCTION greater girth of t
. The structure and life of birds . | Bones very little or not at all of humerus. Logger-headed Duck . Scoter Duck Nestor Parrot Red-throated Diver .Spur-winged Goose . l3 TS a 4 I These measurements speak for themselves, evenwithout any exact statement of the weights of thebirds ; but the following illustration will do more toexplain the problem of hollow bones. The shoulderbones of a Skua Gull, which has scarcely any aeration,of a vociferous Sea Eagle, and a Hornbill, both of whichare highly pneumatic, are placed side by side. The VI FORM AND FUNCTION greater girth of the hollow bones in proportion to theirlength is at once obvious. But to bring this out stillmore clearly, I have taken the wing bones of the Skua. Humerus of Pomatorhine Skua (a) ; Rhinoceros Hornbill (b); and Vociferous SeaEagle (c). Drawn to scale. as the standard, and calculated what would have beenthe length of the same bones and of the whole wing inthe Sea Eagle and the Hornbill, if they had been builtupon the same lines ; ri2 THE STRUCTURE AND LIFE OF BIRDS chap. Skua ...... Sea Eagle . .Rhinoceros Hornbill Humerus. Aggregate Length of\\ ing Bones. Girth ofHumerus. ActualLength. It uLength pro- , , Length pro-portionate TActuau1 Portionateto Girth. Length. to Girth ofHumerus. £f inches 4! inches f 5 Aa if „ 4s » 4§ inches 13* 13I7^0- ,, 2oTv 22^ 7^ „ i5l 23H ! Thus, if in the Sea Eagles humerus length wereproportioned to girth, the bone would be more thanhalf an inch longer ; on the same principle the aggre-gate length of the wing bones would be greater by morethan one and a half inch ; the Hornbills wing wouldbe lengthened by more than eight inches, its humerusby more than three ! If now we take a fine saw andcut
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructurelif, bookyear1895
