摘要：The luminous reflectance of the skin has been measured in a sample of 87 monozygotic, 14 dizygotic (like-sexed) and 11 unlike-sexed twin pairs aged from 12 to 18 years, using the Phtovolt photoelectric reflection meter (Mod. 610). Measurements were taken with the green tristimulus filter designed to represent lightness of colours, on the outer and inner surfaces of the upper arm, to which those on the forehead, chest, shoulder and back of the hand were occasionally added.Although the number of dizygotic twin pairs in the sample was not satisfactorily large, the following conclusions may be drawn tentatively from the results obtained.1. The measurement technique is sufficiently sensitive in determining the extragenic influences on monozygotic twin pairs, if the deviation due to measurement error in two successive reflectance readings can be kept within 1.0%.2. The comparison of mean monozygotic and mean dizygotic intrapair variances provides a highly significant difference, indicating a strong genetic component in the variability of the skin lightness. On the other hand, the mean interpair variance obtained from monozygotic twin pairs usually reveals no statistically significant increase over the mean dizygotic intrapair variance.3. The lightness mean values differ markedly between body areas and, in the higher age groups, between both sexes, the female being significantly lighter.The mean intrapair variances, however, do not seem to be affected seriously by these factors.4. It was suggested that an increase in skin reflectance values, probably due to the puberty changes of the endocrine status, may take place more markedly and slightly earlier in females (12-15 years) than in males (13-18 years). No significant difference of the mean intrapair variances was found, however, in both sexes between lower and higher age groups. A longitudinal twin study during the pre-puberty period may help to solve the problem.
