Abstract
From an egg produced under the weakening influences of “reproductive overwork” a female pigeon was hatched (in 1914) which showed a marked lack of power over the voluntary movements of the head and body. This lack of coördination was practically completely lost in the adult bird. The affected female was bred to two different males. The derangement has been inherited through four generations descended from either male.
The affected offspring have shown many degrees of the lack of muscular control (birds demonstrated). Some have shown marked disturbances when young and have later recovered. Others have at first been classed as normal and have later developed marked irregularity of movement. The more usual manifestations of the disorder are: Nodding of the head, or nodding and swaying of the head and neck; unsteady gait; tipping (somersaulting) backwards or forwards; falling on the side; very irregular flight, the bird even flying backwards. The same bird often exhibits two, three or perhaps all of these irregularities. Practically all affected birds are unable and uninclined to sit on a perch, remaining constantly on the ground, or on a flat ledge. In the most affected individuals there seem to be no movements whatever of wholly normal coördination; in average cases, however, the disturbances are much increased under excitement, fear, or any attempt at increased or more vigorous movement. In a few cases the movements have seemed fairly normal when the bird was at perfect rest. Several of the affected birds have mated and produced young. Offspring from two affected birds have not yet been obtained.
About 175 young have been reared to the age at which the disorder might be exhibited. Of this number 119 were classed as normal and 46 as affected.
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