Page:Popular Science Monthly Volume 75.djvu/314

310 of vision, which is by Miss Amy Barrington and Professor Karl Pearson, is of special interest, as it is one of the first attempts to determine the relative influence of heredity and environment, and announces the unexpected conclusion that there is no definite evidence that schools have a deleterious effect on the eyesight of children. Other results are that keenness of vision is an inherited character, that there is some relation between intelligence and good eyesight, but none between this and poverty or shiftless parentage.

The authors have not obtained data of their own, but work over results that have already been published. For heredity they discuss the work of Steiger, which has the drawback that the material is not a random selection from the population, but starts with abnormal cases. Allowing for this, they conclude that heredity is as strong in the case of astigmatism as for other physical traits, such as height or eye color.

For environment the authors depend largely on a study of 1,400 school children made by the Edinburgh Charity Organization Society. These children show a high degree of fraternal resemblance. The conditions of eyesight are reproduced in the accompanying diagram. It appears that emmetropia—which the authors regard as synonymous with normal vision, though there are good grounds for regarding the hypermetropic eye as normal—actually increases, from the age of six to ten, while astigmatism decreases. There is no appreciable change in myopia. Myopia, or near-sightedness, does increase from the age of ten to fourteen, though only to 6.5 per cent, of the children.

These figures do not agree with those of Cohen, Erismann, Risley and other investigators. Cohen, for example, found the percentage of myopics to be: in village schools 1.4 per cent., in elementary schools 6.7 per cent, in intermediate schools 10.3 per cent., in the gymnasium 26.2 per cent, and in the university 59.5 per cent. The fact is that the Edinburgh children, being from the poorest classes, probably did not greatly strain their eyes with reading and school work. The authors say: "The persistent use by the Germans