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class of animals, arid in no other part of birds ; 

 tough, light, pliant, elastic. The pith, also, 

 which feeds the feathers, is amongst animal sub- 

 stances, sui generis; neither bone, flesh, mem- 

 brane, nor tendon. 



But the artificial part of a feather is the beard y 

 or, as it is sometimes called, the vane. By the 

 beards, are meant what are fastened on each 

 side of the stem, and what constitute the breadth 

 of the feather, what we usually strip off from 

 one side or both, when we make a pen. The 

 separate pieces, or lamina, of which the beard 

 is composed, are called threads, sometimes fila- 

 ments or rays. Now, the first thing which an 

 attentive observer will remark is, how much 

 stronger the beard of the feather shows itself to 

 be when pressed in a direction perpendicular to 

 its plane, than when rubbed, either up or down, 

 in the line of the stem ; and he will soon discover 

 the structure which occasions this difference, 

 viz. that the lamina?, whereof these beards are 

 composed, are flat, and placed with their flat 

 sides towards each other; by which means, 

 whilst they easily bend for the approaching of 

 each other, as any one may perceive by drawing 

 his finger ever so lightly upwards, they are much 



D2 



