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[Report read at a meeting of the Manchester and Salford Sanitary

Association, April 26th, 1904.] THE first International Congress on School Hygiene met in Nürnberg (Bavaria) on the 4th of April.* The Congress was under the patronage of His Royal Highness Dr. Prince Ludwig Ferdinand of Bavaria, who has qualified as a Doctor of Medicine. The President was Professor Griesbach, M.D., whose work on the estimation of brain fatigue, by the use of the æsthesiometer is well known.

The Congress was opened by His Royal Highness Dr. Prince Ludwig Ferdinand, and addresses were delivered by delegates from almost all civilised countries. About 1,400 medical men, teachers, and others interested in school hygiene attended the Congress. There were eleven sections, and 180 papers and addresses were contributed.

After the congratulatory addresses, which occupied about two hours, came the first and most important paper of the Congress, by Prof. Cohn, of Breslau, the subject being :What have Ophthalmic Surgeons done for School Hygiene, and what remains for them to do?

For forty years Prof. Cohn has worked steadily at the relation of school work to failure of vision, and his results are of the greatest value. His lecture was illustrated by many beautiful diagrams and models. Cohn believes that school work improperly conducted is an important factor in the causation of short-sight or myopia. As a test for vision, Cohn employs the following letter:


* The writer had the pleasure of attending the Congress as a delegate from the Victoria University of Manchester and the Manchester and Salford Sanitary Association.

A letter of this size, should be seen with each eye separately at a distance of six metres. It may be used for testing the vision of children and of illiterate persons. The letter is turned in various positions, and the person whose vision is being tested indicates the position of the letter with a fork which has three broad short prongs, resembling the transverse limbs of the letter. From his examinations of the vision of 10,000 school children he has drawn the following conclusions :

1. The number of short-sighted children increased the more advanced the school. In village schools the percentage of cases of myopia was 1, in elementary schools 6, in the middle schools 10, in the advanced schools (gymnasien) 26.

2. The number of cases of short-sight increased steadily in all schools, from the lowest to the highest class.

3. The average of the degree of myopia increased from class to class.

In Germany Cohn found that the percentage of myopic scholars, in the classes of 24 advanced schools (gymnasien), rose from 22 in the lowest class to 58 in the highest. Cohn's recent examination of students in Breslau showed that 60 per cent. were short-sighted.

The exact primary cause of myopia is still unknown; but the defect is undoubtedly increased by eye-strain, caused through prolonged work near to the eye, by hereditary tendency, and by the deficient lighting of rooms. One very important cause of myopia is the eye-strain produced during school life through the small type of books. Cohn has carefully studied the type and mode of printing of school books which is desirable, in order that eye-strain and myopia may be prevented or diminished. The following are his conclusions:--The height of the smallest n (this letter being taken for measurement) should not be less than 1:5mm., the least distance between two lines of print 2-5mm., the thickness of the stroke of a letter not less than 0:3mm., the greatest length of the line 100mm., and the greatest number of letters in one line 60.

Cohn recommends the following simple method of determining whether the printing of any book or paper is of the satisfactory character just described :-In the middle of a thin card (or visiting


card) a square hole is cut, each side of which measures exactly one centimetre.

Size of hole : Square centimetre. The card with the centimetre square hole is placed on a page of the book or paper to be tested, the lower edge of the square being immediately above a line of print. If the type be satisfactory only two lines of print can be seen within the centimetre square. According to Cohn, the type of all books should be condemned in which more than two lines are visible in the centimetre square, measured in the manner just described. The print of many books and papers is so small that three or four lines are visible in the centimetre square. In maps the letters are often exceedingly small (0:6 to 0:5mm. in height), and hence great eye-strain is produced. Cohn draws attention to the bad effect on the eyes

of the highly glazed paper, now so frequently employed, especially in American books. The printed letters should be deep black. Letters of a faint or faded black colour are more difficult to read than those printed deep black.

Prof. Cohn then considered the lighting of school-rooms, and pointed out the necessity for attention to this question in order to diminish the risk of myopia developing amongst school children. He described the methods of examination of the lighting of schoolrooms. It is necessary to ascertain in the case of every scholar whether he can see writing at a distance of 33cm. whilst seated at his desk. As regards the windows of the school-room, there are many points which require attention. The lower border should not be less than one metre from the floor. Cohn thinks that windows facing the east or south-east give the best light, but if the direct rays of the sun should be too powerful, suitable curtains or shades will be required. Förster recommends windows facing the north in order that the use of curtains or shades may be avoided. The height of the buildings opposite the school is important; if they should be too high the school-rooms are made dark. Cohn thinks the total window surface should be at least one-fifth of the floor area. The higher the windows the better. The scholars should sit so that the light comes from their left side. The light of a school-room is measured most accurately by means of Weber's photometer. It is also desirable to ascertain how many of the scholars, when seated at their desks, are unable to see the sky through the windows. Cohn thinks that the desks in all parts of the school-room at which the sky cannot be seen should be condemned. In France, Javal has recommended that every scholar should be able to see, through the window, a portion of the sky which corresponds to a point, at least, 30cm. from the upper border of the window. This is easily determined by fixing a strip of paper on the window, 30cm. from its upper end, and then

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noting from which desk seats in the school-room the portion of the sky seen through the window does not extend beyond this strip of paper. All seats beyond this limit (i.e., in which less of the sky is seen) are unsatisfactory.

Cohn has constructed a special apparatus for testing the lighting of school-rooms. In a well-lighted room small figures can be read at a distance of 40cm. without difficulty, and the rapidity with which they are read is of importance. Cohn's apparatus is based on the rapidity with which figures are read, at different parts of the room, when light is cut off to varying degrees.

The apparatus consists of a wooden eye-piece A, which is held before the eyes like a stereoscope. Behind this are three vertical

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pieces of grey glass, G1, G2, G3, which can be removed from their position in front of the eyes (as in G3). The light-absorbing power of these glasses has been determined photometrically. On a horizontal bar, M,, M,, is a movable block E, to which is fixed a table of 12 vertical rows of figures (F). Close by the window, on a clear day at noon, these figures can be read correctly and easily at a distance of 40cm. by the normal eye, the glasses being removed. The medical man asks the scholar to read as rapidly as possible, and with a watch the time is noted. The figures on the chart are all double, as 24, 36, etc. At least 20 figures should be read in 30 seconds. In a room lighted artificially, if 20 figures can be read in the manner described in 30 seconds, the lighting is satisfactory. In daylight the examination is made in the following manner :-All three of the grey glasses are placed in front of the eye-piece. The scholar closes his eyes for two minutes, in order to become accustomed to the darkness, and then opens the eyes and attempts to read the figures through the grey glasses. If the light is very bright the scholar is able to read the figures through the three glasses almost as rapidly as when the apparatus is used without the glasses. The three glasses together absorb about 99 per cent. of the light, and thus the illumination is only 1/100th part of the daylight. The lighting is excellent in those parts of the room in which the figures can be read easily through all three glasses. Where the scholar cannot read so many figures with the three glasses before the eyes as without the glasses, then an examination is made with two glasses only in front of the eyes. These two glasses absorb 95 per cent. of the daylight. If the scholar can read easily as many figures with the two glasses as without the glasses, the lighting of that part of the room is good. If this is not possible, then an examination is made with only one glass before the eyes. This absorbs 80 per cent of the light (i.e., only one-fifth of the daylight

. is transmitted). If as many figures are read in half a minute with the one grey glass in front of the eyes, as without the glass, the part of the room examined is satisfactorily lighted. But if this is not possible (the distance of the figures being 40cm. from the eyes) then the part of the room examined is insufficiently lighted, since the daylight often sinks to one-fifth in a few


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