58 The Microscope. 



rind or all pith ? Following Dr. Carpenter's account 

 of it, I have to state that it approaches most to the 

 latter condition, but is peculiar in its structure. When 

 the focus of the microscope is very carefully adjusted, 

 I can see a thin transparent layer edging each side of 

 the hair, just as in the deer's hair. Within this layer 

 is the cellular substance that constitutes the principal 

 part of the hair, the numerous straight lines marking 

 the form which the cells have taken. The hair owes 

 its hue to the pigment contained in some of the cells ; 

 and the grey colour which gradually steals through 

 one's hair, placing a line of silver here and there, is 

 caused by the absence of the pigment. 



A section made transversely (that is, across, as 

 you would slice a cucumber, or cut a lemon in two) 

 shows the outer rind of the hair clearly as a trans- 

 parent structure. Occasionally there is a distinct line 

 of large cells in human hair in the centre of the small 

 and lengthened ones, giving an appearance somewhat 

 resembling that in the larger hair of the horse, and 

 some writers regard these as the only portion properly 

 called medullary ; but good reasons have been given 

 for considering both kinds of cells as equivalent to the 

 medullary substance in other hairs, and giving the 

 appellation of " cortical " to the thin transparent out- 

 side layer, and the delicate overlapping scales, which 

 show on a specimen mounted dry. The examination 

 of the root of a hair is easily managed, and interesting 

 when a high magnifying power is at command. The 

 root should be placed on a glass slide, with only a 

 small portion of the hair, and in a drop of water. A 



