HAIRS, FEATHERS, AND SCALES. 7 



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

 look through them endwise. 



Here is one, very suitable for examination (6), 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 distinguished at 

 once by the conspicuousness of the medullary 

 portion, which is thick, and quite opaque, 

 and is broken up (especially towards each ex- 

 tremity 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 ^oV^th to -^th of an 

 inch ; and there are, upon an average, about 

 two imbrications in a space equal to the dia- FIBRB OP 

 meter. No colour is perceptible in these spe- 8HEEP ' S WOOL - 



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

 on the roof of a house. 



