HAIKS, FEATUKKS, AND SCALES. 7 



[ take up a few of the dust-like atoms witli tlie point of 

 my pen -knife, and scatter tliem on tliis plate (or slide) 

 of glass, and these I cover with another plate of thin 

 glass ; for this dust is composed of thin transverse slices 

 of the bristles, and as I scatter them, some will fall 

 upon their cut ends, so that we shall look through them 

 endwise. 



Here is one, very suitable for examination, — since it 

 is not a whole section, the razor having passed some- 

 what obliquely across it, coming out beyond the mid- 

 dle, 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 wh<»le substance appears made up of exces- 

 sively 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 me- 

 dullary cells, 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 couspicuousness 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 imbrica- 

 tions, proportionally much fewer than those of human 

 hair, while the diameter is also much less. Thus these 

 examples, selected fi-om fine flannel and fi'om coarse 



