STRUCTURE OF BIRDS 



inserted in the skin, is hollow ; higher it becomes 

 the shaft, which is solid, with a groove down the 

 centre, from both sides of which the vane, the fine 

 filaments, which can be expanded or contracted, 

 spring. At one time it was believed that these 

 filaments contained " natural oil," which in the 

 case of water-fowl, served to keep the feathers 

 dry ; now it is known that the filaments can be 

 brought together so tightly that all moisture is 

 excluded. This is done by the muscular action 

 of the living bird ; if the dead body of any water 

 fowl be placed in water, the feathers at once 

 become soaked and sodden. 



The growth of feathers is a process entirely 

 different from the growth of hair in mammals. 

 The embryo feather, with quiU, shaft, and vane 

 complete, is moulded in a minute capsule, which 

 appears above the skin ; the feather then appears, 

 and slowly develops to its full size. This process 

 is repeated more or less completely at every moult 

 the new feather forcing out the old. Light, 

 strong, and elastic, the material of which a feather 

 is composed, is not to be found elsewhere in nature. 

 It is neither bone nor flesh, membrane nor tendon ; 

 it has definite work to perform, and possesses 

 a constitution peculiarly its own. 



The miracle of the growth of a feather — so 

 simple yet so complex, and destined to fulfil 

 so many pre-conceived ends — was one of the 

 marvels in nature that led Alfred Russell Wallace 

 to declare his fixed belief in a Higher Intelligence 

 that works apart from the mentality of the 

 organism itself. 



In a letter on this subject to the author he 

 wrote : — " How all the infinitely complex and 

 wonderfully regular processes of growth and 

 development of living things actually occur, how 



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