REPORT OF THE ANTHROPOMETRIC COMMITTEE. 



135 



Class I. — Peofessional Classes. — Table XI., showing the Colour of Hair 

 and Eyes, and their relation to each other, of 1027 Men and Boys 

 from ages 10 to about 50 years. 



physiological relations to each other. The iris, on which the colour of the 

 eye depends, is a thin membranous structure composed of unstriped mus- 

 cular fibres, nerves, and blood-vessels, held together by a delicate network 

 of fibrous tissue. On the inner surface of this membrane there is a layer 

 of dark purple pigment called the uvea (from its resemblance to the colour 

 of a I'ipe grape), and in brown eyes there is an additional layer of yellow 

 (and pei'haps brown-red) pigment on its outer surface also, and in some 

 instances there is a deposit of pigment amongst the fibrous structures. 

 In the albino, where the pigment is entirely absent from both surfaces of 

 the iris, the bright red blood is seen through the semitransparent fibrous 

 tissues of a pink colour ; and in blue eyes, where the outer layer of pig- 

 ment is wanting, the various shades are due to the dark inner layer of 

 pigment — the uvea — -showing through fibrous structures of different 

 densities or degrees of opacity. The eyes of new-born infants of both 

 white and black races (and I believe the new-born young of all the lower 

 animals) are dark blue, in consequence of the greater delicacy and trans- 

 parency of the fibrous portion of the iris ; and as these tissues become 

 thickened by use, and by advancing age, the lighter shades of blue, and 

 finally grey are produced; the grey, indeed, being chiefly due to the 

 colour of the fibrous tissues themselves. In grey eyes, moreover, we see 

 the first appearance of the superficial layer of yellow pigment in the form 

 of isolated patches situated around the margin of the pupil, or in rays 



