596 NEAR SIGHTEDNESS IN SCHOOL CHILDREN. 



the page is in the shadow. It results also from improperl}' graded desks, 

 from small and poor type and inferior printing-ink, and from faulty color 

 ivnd quality of printing-paper; also from pale writing-ink — pale when 

 used — and from the substitution of the lead pencil for the pen, especiallj^ 

 in the evening. 



5. A prone or forward position of tlie head too long maintained or fre- 

 quently repeated, and becoming a habit. This results from reading or 

 studying wiih the book in the lap and from the use of desks not graded to 

 the height of the pupil. Dr. Howe reports pupils var^'ing eighteen inches 

 in height seated at the same grade of desks. The distance of the eye from 

 the page should not be less than twelve nor more than eighteen inches. 

 Having the desks set too far from the seats also induces this faulty posi- 

 tion. The front of the desk should overlap the seat one or two inches. 



Bonders says:' "In the hygiene ol myopia the very first point is to guard 

 against working in_ a stooping position.' He favors high, sloping desks, 

 and indicates 'rectilinear drawing on a fiat surface' as a class of work which 

 is especiallj^ objectionable. 



6. Since a vitiated atmosphere is a frequent feature of the school room, 

 it may not be amiss to add here that the effect of bad air is indirectly to 

 iniure, if not to destroy, the sight." 



Three kinds of eyes are recognized in this discussion, namely: Normal, 

 near sighted and long sighted. The first brings the raj^s of light to a focus 

 on the retina; the second, in front of the retina; and the last, behind it. 

 The difference in eyes consists, chiefly in the direction of the axis of the 

 eye from front to back, and also in the convexity of the crystalline lens. 



A pertinent question is, what change, if any, is produced in the shape 

 of the eye to accommodate it to objects whether near or remote? 



To explain how near sightedness is produced, some contend that when 

 the object is near, the muscles that turn the eyes toward the nose press on 

 the eyeballs, elongating them and consequently increase the elliptical form 

 of the crj^stalline lens, and that this is the cause. 



Admitting this to be correct, how can it be demonstrated? is a question 

 that will p,:zzle, I apprehend, the author of the article in the Popular 

 Science Monthly as well, as Dr. Wm. Dickinson, who has written on the same 

 subject in the American Journal of Education. The question thus present- 

 ed is. How does the qjq adjust itself? By external ])ressure of the inside 

 muscles? By a forward or retrograde movement of the crystalline lens be- 

 tween the aqueous and vitreous humors? Or b}^ contractions and relaxa- 

 tions of the suspensory ligaments and ciliary muscles? 



Let us proceed to test these theories. 



Hold the flame of a candle near a person's eye and a little to one side, 

 and look into the eye from a proper distance, and three images of the flame 

 will be seen, two upright, and one inverted. The cornea reflects one up- 

 right image, and the front of the crystalline lens the second, while the 

 third is reflected from the concave surface of the back part of the crystal- 

 line lens. 



