vii FLIGHT 2ii 



line with the forearm, the result will be that the 

 hand will be pulled hard against the wrist. This will 

 help the ligaments to resist the very great strain put 

 upon them. The wonder is that, with all its strength, 

 the wrist joint does not succumb. 



(4) The air, to a considerable extent, determines 

 the movement of the wing. This will be explained 

 more fully later on. 



(5) There are muscles which rotate the great 

 secondary feathers and hold them in the best position 

 to make the wing impervious to air. All the great 

 wing feathers are so shaped that the action of the air 

 upon them assists the muscular machinery. 



Such is the wing, at once strong and light ; pliable or 

 stiff, according as pliability or stiffness is needed at 

 different parts, or at different times ; quickly spread 

 and quickly flexed, capable of the nicest adjustment 

 to suit every phase of flight ; worked by machinery, 

 all the weightier part of which is massed upon the 

 body or close to it, and turning on a pivot which 

 stands firm under all pressure. 



Weight of the Breast Muscles. 



To realise how important are the muscles that 

 lower the wing, it is only necessary to know what 

 proportion their weight bears to that of the whole 

 body. I have weighed those of two Wood-pigeons 

 and two domestic pigeons, and have found in each 

 case that they accounted for either just under or just 

 over one fifth of the total weight, In one of the 



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