Mendelian heredity in man / by C.C. Hurst.

  • Charles Chamberlain Hurst
Date:
[1912]
Catalogue details

Licence: In copyright

Credit: Mendelian heredity in man / by C.C. Hurst. Source: Wellcome Collection.

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    the fineness or coarseness of the structure of the iris, conse¬ quently baby-blue eyes may develop into adult grey eyes. Duplex eyes maybe any colour from “ black” (very dark brown) to blue, according to the amount of brown pigment present on the front of the iris. If the amount of brown pigment is small such Duplex eyes may be easily mistaken for Simplex when viewed at a short distance or in a bad light. A close lateral inspec¬ tion in a good light will, however, generally determine the presence or absence of visible pigment in front of the iris, with¬ out the assistance of a lens. An attempt to differentiate the various grades of blue and grey Simplex eyes has so far proved unsuccessful owing partly to their apparent continuity and partly to their changes with age. An attempt to differentiate the various grades of Duplex eyes has been more successful, though experience shows that great caution is necessary to avoid the many pitfalls that exist even for the wary. In 1907 the writer suggested that Duplex eyes might be classified into three definite patterns, Self, Ringed, and Spotted. In the Self pattern, the brown pigment is distributed over the entire surface of the iris, the rays being pigmented to the periphery. To this class belong eyes generally known as “ black,” dark brown, brown, red-brown, yellow-brown, green- brown and green, according to the density of the melanic pig¬ ment covering the front of the iris, and possibly also in some cases to the existence of a distinct yellow or orange pigment (lipochrome) diffused with the brown melanin. In the Ringed pattern the brown pigment is confined to a ringed area round the pupil, leaving a solid blue or grey rim round the periphery. In some cases the ring of pigment is clearly defined and narrow, while in others it is irregular in outline and broader with fimbriated rays. To this class belong eyes generally known as grey-brown, dark grey, grey, grey-green, and blue- green. In the Spotted pattern the inner ring is altogether absent or broken up into discrete patches, blotches or spots. These spots are usually irregular in size, number and distribution over the blue or grey ground colour. Similar spots are to be found