Page:Popular Science Monthly Volume 19.djvu/67

Rh average of the results of the examinations in twenty-five German and Swiss gymnasia with 9,096 scholars, the percentage of short-sighted pupils rose from the sexta to the prima as follows: 22, 27, 33, 46, 52, 53.

These numbers speak plainly enough. Still there are persons who doubt that children become short-sighted at school. In order to make this more clear, I examined the pupils of the Friedrichs Gymnasium at Breslau in 1871, and repeated the examinations upon the same persons three semesters afterward. Seventeen pupils who had been found normal-sighted at the first examination had become short-sighted, and more than half of those who had appeared near-sighted at first had become more so. Similar results have been obtained by Dr. A. von Reuss in the Leopold Stadt Gymnasium at Vienna, by Dr. Seggle in the Cadet Corps at Munich, and by Dr. Derby at Boston.

It is evident that we are threatened with a great national affliction, which is likely not only to be detrimental to all peaceful occupations, but to impair the military efficiency of our people. It is important to seek out the causes of this ever-growing evil and contest them with energy. We can not discuss here all the causes that tend to produce myopy. All protracted looking at close objects may contribute to it. Among the more active causes may be mentioned badly-constructed school-benches, imperfect lighting, too much reading, bad writing, and bad type. The matter of the style of typography which is most compatible with the preservation of the eyesight deserves especial consideration. The most important point is the size of the letters. We can not determine this by the measurement of the em, as the printers do, for that regards the shank of the type, of which readers know nothing; but it must be judged by a special measurement of the visible letter. I have adopted as the standard of measurement the letter n, that being the most regular and symmetrical in shape in both the Roman and German alphabets. I have found that the n in pearl type is about 0·75 millimetre (or about 3/100 of an inch) high, in nonpareil 1 millimetre (or about 1/25 of an inch), in brevier (petitschrift) 1-1/4 millimetre (or about 1/20 of an inch), in long primer (corpusschrift) 1-1/2 millimetre (1/17 inch), and in pica (Ciceroschrift) 1-3/4 millimetre (1/14 inch).

We have hitherto had no definite rules concerning the smallest size of letters which should be permitted for the sake of the eyes. The distance at which a letter of any particular size can be seen does not afford a guide to it, for it does not correspond at all with the distance at which matter printed in the same type can be read steadily, at the usual distance in reading. I believe that letters which are less than a millimetre and a half (1/17 inch) high, will finally prove injurious to the eye. How little attention has hitherto been paid to this important subject is exemplified in the fact that even oculistic journals and books