COMPARATIVE ANATOMY. 147 



tlie air, and in which their strength is wanted and put to 

 the trial. 



This is one particularity in the structure of a feather -, a 

 second is still more extraordinary. Whoever examines a 

 feather cannot help taking notice, that the threads or lami- 

 nae of which we have been speaking, in their natural state 

 li?tite — that their union is something more than the mere 

 apposition of loose surfaces — that they are not parted asun- 

 der without some degree of force — that nevertheless there is 

 no glutinous cohesion between them — that therefore, by 

 some mechanical means or other, they catch or clasp among 

 themselves, thereby giving to the beard or vane its closeness 

 and compactness of texture. Nor is this all : when two 

 laminae which have been separated by accident or force are 

 brought together again, they immediately reclasp ; the con- 

 nection, whatever it was, is perfectly recovered, and the 

 beard of the feather becomes as smooth and firm as if noth- 

 ing had happened to it. Draw your finger down the feather, 

 which is against the grain, and you break probably the 

 junction of some of the contiguous threads ; draw your fin- 

 ger up the feather, and you restore all things to their for- 

 mer state. This is no common contrivance : and now foi 

 the mechanism by which it is cfi^ected. The threads oi 

 laminae above mentioned are interlaced Avith one another ; 

 and the interlacing is performed by means of a vast number 

 of fibres or teeth, which the laminae shoot forth on each 

 side, and which hook and grapple together. A friend oi 

 mine counted fifty of these fibres in one-twentieth of an inch. 

 These fibres are crooked, but curved after a different man 

 ner : for those which proceed from the thread on the side 

 towards the extremity of the feather, are longer, more flex- 

 ible, and bent downwards ; whereas those which proceed 

 from the side towards the beginning or quill end of the 

 feather, are shorter, firmer, and turn upwards, The pro- 

 cess, then, which takes place is as follows : when 1 wo lam- 

 inae are pressed together, so that these long fibres are forced 



