HAIRS, FEATHERS, AND SCALES. 



them, some will fall upon their cut ends, so that we shall 

 look through them endwise. 



Here is one, very suitable for examination (b), — since it 

 is not a whole section, the razor having passed somewhat 

 obliquely across it, coming out beyond the middle, where 

 it thins away to an edge. The outline is not circular, 

 but elliptical; that is, the hair is not round, but flattened. 

 There is no separable cortex, or bark, and the whole sub- 

 stance appears as if made up of exceedingly fine fibres, of 

 which we see the ends cut across. A rough dark line 

 occupies the middle of the slice, in the plane of the 

 greater diameter ; but at the edge of the slice we are able 

 to see that this is not a solid core, as has been sometimes 

 supposed, but a cavity passing up through the hair. It is 

 surrounded by a layer of cells, called medullary, and 

 which appear black, because they are filled with air. 



The finer hairs of the Horse and the Ass, 

 such as those selected from the cheeks, have 

 the sinuous edges of the plates about as 

 close as in human hair. But they are dis- 

 tinguished at once by the conspicuousness of 

 the medullary portion, which is thick, and 

 quite opaque, and is broken up (especially 

 towards each extremity of the hair) into 

 separate longitudinal irregular masses. 



The fine wool of the Sheep is clothed with 

 imbrications, * proportionally much fewer than 

 those of human hair, while the diameter is 

 also much less. Thus these examples, selected 

 from fine flannel and from coarse worsted, 

 vary in diameter from ^^th to T £ -^th of an 

 inch ; and there are, upon an average, about 

 two imbrications in a space equal to the dia- 

 meter. No colour is perceptible in these spe- SHFKP ' S woot " 



FIBRE OF 



* A structure is said to be imbricated when it is arranged like tiles 

 on the roof of a house. 



