Hairs and Feathers. 53 



ing, the shrivelled remains of which in a full- 

 grown quill must be familiar to every one who has 

 mended a pen. 



The quill of a feather, then resembles the root of 

 a hair; and in like manner, its stem, namely, the 

 remaining part of the feather, corresponds to the shaft 

 of the hair. When you have mended the same pen so 

 often that very little quill is left, you will observe by 

 cutting off its last remnant, that the stem of the 

 feather consists of a horny sheath enclosing a white 

 pith-like substance. These two parts have received 

 the names of the " cortical " and " medullary " sub- 

 stances ; and closely correspond with the component 

 parts of hairs, as shown by the microscope. The 

 minute size of hairs as compared to feathers is an 

 obstacle to our readily understanding their structure ; 

 on the other hand, the beautiful transparency of the 

 outside, or " cortical substance," enables us to view 

 them to great advantage when assisted by a good 

 microscope. The figures in Plate V. give representa- 

 tions of the appearance of various hairs when highly 

 magnified. Let us examine the first of them, namely, 

 the white mouse's hair, represented in Plate V., fig. 1. 

 Those who are shown it for the first time are sure, 

 after a brief survey, to look round appealingly for an 

 explanation of what they have seen, the object is so 

 unlike anything in their previous experience. It 

 resembles a number of beautiful glass rods of various 

 thickness, each containing a running pattern in its 

 centre. That running pattern engrosses all attention 

 at first; and next comes the question, why are tho 



