DIPLOPIA MONOPHTHALMICA. 271 



clock " suspended on the wall, or with appropriate illustra- 

 tions given in Snellen's " Test-types" 



(d.) Construct a series of concentric circles of equal thick- 

 ness and tint, about one-eighth of an inch apart upon a card. 

 Make a small hole in the centre of the card. Look steadily 

 at the centre of the card held at some distance. All the 

 parts will not be equally distinct. Approach the card 

 towards you, noting in which diameter the lines appear most 

 distinct. 



(e.) This card may be used in another way. Hold the 

 card in front of and with the circles directed towards the 

 eye of another person especially one with astigmatism 

 place your own behind the hole in the card and look into 

 the observed eye, noting the reflection of the circles to be 

 seen in the eye. Observe in which meridian the circles are 

 most distinct, and if there be any perceptible difference in 

 the thickness and distinctness of the circles. 



(f.) Draw a series of parallel, vertical, and horizontal lines 

 of equal tint and thickness, and about one-eighth of an inch 

 apart. Fix the card vertically at a distance, and move to- 

 wards it, noting whether the vertical or horizontal lines are 

 most distinct. 



(g.) Fix a fine wire or needle vertically in a piece of wood 

 moving in a slot, and similarly fix another needle or wire 

 horizontally. Move the needles until both can be seen 

 distinctly at the same time, when it will be found that the 

 needles are some distance apart, usually the horizontal one is 

 the nearer. 



12. Diplopia Monophthalmica. 



(a.) Make a small hole in a black card, hold it at some 

 distance, and with one eye look at a luminous point, the 

 eye being accommodated for a distant object. One sees 

 either several objects (feeble light) or an irregular radiate 

 figure with four or eight rays. Move the paper and the 

 long rays remain in the same position. Compare the figure 

 obtained from the other eye. It will very likely be different. 



