. A history of British birds . reat distance from London. + This rust-colour, which has been much insisted upon, is found on manybirds, especially waterfowl, and is known to be due, in their case, to the presenceof peroxide of iron in the water which they frequent. — [Ed.] 320 ANATID^. from tlie Whooper than in its external characters. Themost obvious difference is in the trachea, which forms one ofthe best distinctions in the separation of nearly-allied speciesthroughout this numerous family. The tube of the wind-pipe is of equal diameter throughout, and descending infront of the neck enters
. A history of British birds . reat distance from London. + This rust-colour, which has been much insisted upon, is found on manybirds, especially waterfowl, and is known to be due, in their case, to the presenceof peroxide of iron in the water which they frequent. — [Ed.] 320 ANATID^. from tlie Whooper than in its external characters. Themost obvious difference is in the trachea, which forms one ofthe best distinctions in the separation of nearly-allied speciesthroughout this numerous family. The tube of the wind-pipe is of equal diameter throughout, and descending infront of the neck enters the keel of the sternum, which ishollow, as in the Whooper, traversing its whole arrived at the end of the keel, the tube then,gradually inclining upwards and outwards, passes into acavity in the sternum destined to receive it, caused by aseparation of the parallel horizontal plates of bone, formingthe posterior flattened portion of the breast-bone, and pro-ducing a convex protuberance on the inner surface. The. tube also changing its direction from vertical to horizontal,and reaching within half an inch of the posterior edge, isreflected back after making a considerable curve, till it oncemore reaches the keel, again traversing which, in a lineimmediately over the first portion of the tube, it passesout under the arch of the merrythought; where, turningupwards, and afterwards backwards, it enters the body ofthe bird to be attached to the lungs in the usual is the state of development in the oldest bird theAuthor met with. The degree next in order, or younger,differs in having the horizontal loop of the trachea confinedto one side only of the cavity in the sternum, both sides of BEWICKS SWAN. 321 the cavity being at this time formed, although the loop ofthe tube is not yet sufficiently elongated to occupy the wholespace. The third and right-hand one of the three represen-tations below, from a still younger bird, possesses only thevertical insertion o
Size: 2244px × 1113px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsaun, bookcentury1800, bookdecade1870, booksubjectbirds
