Life and Medical Sciences
Cell & Developmental Biology
Wiley InterScience Backfile Collection 1832-2000
A histological study was made in the guinea-pig of the distribution of melanin pigment in the normal dark-eye and in various mutant types, such as the brown type of dark-eye (b), light and dark salmon-eye (sm), dark red-eye (crB), brown red-eye (crb), albino (ca), pink-eye (p), and pseudopink-eye (P sm b). The genes which affect pigmentation in the eye have definite qualitative or quantitative effects on the production of melanin. Eyes of the genetic constitution ca, p, or sm possess very little pigment. But eyes which have the dominant allelomorphs of these genes, C, P, or Sm, have a large amount of pigment. The non-yellow gene, cr, and the brown gene, b, cause the deeper retinal layer, which is normally intensely pigmented throughout its entirety, to become less pigmented. There is a corresponding reduction in the melanin in the pigmented areas of the iris and choroid. In all types of eyes with reduced pigment, such as the albino, pink-eye, and pseudopink-eye, pigment persists in the deeper retinal layer even when it is almost absent from other regions. Moreover, in all eyes which have less pigment than the normal type there is a decided tendency for chromatophores to be located adjacent to blood vessels. This tendency is outstanding in the iris and quite noticeable in the choroid.
Type of Medium: