OCR Text |
Show 284. DOMESTIC DUCKS. CIIAI'. Vlll. tho pelvis than in the wi. ld duck. The Ayles b ury d uc k has fifteen cebr vi.c afl and ton dorsal vortobrro furru.s hc d Wl" th n·· b s, but th· o sn.mo n. umtl er "old lumbar sacral and caudal vcrtobrro, as far as could be traced, as mh b10 well duck. T' ho cer'v ical vcrtobrro m. th1.s same due1 c (f1 g. 4·0 '.D ) wCor)e. roue roa or . th tl . tho wild ( ' so roue 1t so, and thicker relatively to thorr lc~g 1~n m 1 t h f tho ci..,.hth cervical that I have thought it worth wh1lo to glve a s co 0 0 t t:> tl t . h :£ • ·ng statomcn s we see 1a vertebra in the. o two buds. Fro~ t e . orcgoi odificd into a dorsal tho fifteenth cervical vertebra occaswnally becomes m b ,,,6 d vertebra and when th1.s occurs al l tho a a· "ning vortc rro are mow c . ' . . d JOl . .b . · 11 1 ·t bra bcarmg a n lfl occaswna y We also soc that an uddit10nal orsa ver c . . a Jarcntl developed, tho numb r of tho cervical and lumbar vortebrro • PI Y remaining tho same n.s 11sual. . 1 f th I examined tho bony enlargement of tho trachea m ~he ~a cs ~ e Pcnglun, Call, Hook-billed, Labrador, and Aylesbury breeds' and m all it was identical in sl1apc. H 1 b"ll a The f>eluis is remarkably uniform; but in tho skel~ton of tho 00 c- 1 0d duck tho anterior part . h b d · ards · m the Aylesbury an JS muc owe mwc ' ::;orne other broods the J·s chJ·a dw· foramen · 1 longated In tho sternum IS css 0 . · d .· bl' furcula, coracoidR, and scapula, the ruffcrcnccs arc so shght at tl so ;aiJa . 0 as not to be worth notice, except that in two skeletons 0 d 10 cngum duck tho terminal portion of the scapula was ~uch _attc~uatc · ld b In the bones of the leg and mug no modJficatwn m sl~apc cou c observed. But in Pcnglun and Hook-billed dnckR, the tcrmm~l phalanges of tho wing arc a little shortened. In the former, the fcmill: and metatarsus (but not tho tibia) arc considerably lengthcnc_d, rclat1v?ly to th_e Ramo bonos in the wild duck, and to the wing-bon~s :U both b1~·ds. T~s elongation of the leg-bones could b? soon ':hilst the b:rd was a~vc, and 1s no doubt connected with its peculiar upnght manner of walking. In a largo Aylesbury dnck, on the other hand, the ti~ia was the only bone of tho leg which relatively to tho other bonos was sli~htly lengthened .. On the ~IT cts of the increased wnrldcc?·easedUseof theL1:rnbs.- In all tho b1~eds the bones of the wing (mcasmcd separately after haVIng ?oen cloa~cd) rc_lativoly to those of the leg have become slightly shor~cned, m com_panson \~1th the same bonos in the wild duck, as may be soon m tho followmg table.- Name of Bre d. I . Length of Femur 1Lengthof1Iumcrus,l Tibia, and Meta-' l{udius, and M ctu- ~ Or as tarsus together. \ carpus togct~~ ---- -- -,~--Joches. - Jncbcs. .. .. 7•14 9·28 100 : 129 .. ·- 8·64: 10•43 100 : 120 .... .·.- I 8•25 9·83 ~~~ : g~ 1·12 s·7s 2 , 6·20 7•77 100 : 1' 0 Wild m11llard .. .. Aylc~bury .. .. 'l'uf"tccl (Dutch) .. Penguin .. .. .. Cl1ll .. .. .. .. ----- --------~------~----~------ 1 Wild duck (11nother specimen) Common domestic duck .. Length or same I Length of all the Bones. llones of Wing. --l~n~.~~,c~s. --~--i1o1c~oc2;·. -G 100 : 147 100 : 138 CllAP. VITI. EFFECTS OF USE AND DISUSE. 285 In the foregoing table we see that, in comparison with the wild duck, the reduction in tho length of tho bones of the wing, relatively to those of the logs, though slight, is universal. The reduction is least in tho Call-duck, which has the power and tho habit of frequently flying. In weight thoro is a greater relative ruffcrence between the bones of the leg and wing, as may be seen in the following table:- Name of lJrced. Wild mn1lrml .. Aylcsbmy Hooked-bill Tufted (Dutch ) Pen~uin J,nbrador .. Call .. I 'Veight of Femur, I Weight of I Tibi r•, and Humerus, Hadius, Or as Metatarsus. and Metacarpus. ~-- ~~~-- -- ~!i-IS.-- ~~~ H~ I 111 148 100 133 75 90·5 100 120 14L 1G5 100 : l17 . . 1 57 93 1oo : 163 -----, - -- 1 W.r ig!>tofull the Wr igbtofalllhe I Uon s of the . Bones of the l,eg und l~oot. 1 Wing. ~-- Gmit;-- 1--0,::;~-- ~ Wild (anotiJ Cl' specimen) Common dome. tic duck .. I 1g~ I ~~~ I 100 100 173 124 In these domesticated birds, the considerably lessened weight of the bones of tho 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 fl'om the increased weight and length of tho bones of the legs. Tho fhst of the two tables on the next page shows that the legbones relatively to the weight of tho 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 tho result was the same. In the first of these tables we sec 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 bonos can be accounted for only by these domestic birds having used their legs in walking and stanrung much more than the wild, for they never fly, and the more artificial breeds rarely swim. In the second |