XLIX. Miscellaneous experiments.* 



a. Schemer' s experiment. 



(1) Prick two smooth holes in a card at a distance from 

 each other less than the diameter of the pupil. Fix 

 two long, fine needles or straws in two pieces of wood 

 or cork. Fix the cardboard in a piece of wood with a 

 groove made in it with a fine saw, and see that the 

 holes are horizontal. Place the needles in line with 

 the holes, the one about eight inches, the other about 

 eighteen inches from the card. 



(2) Close one eye, and with the other look through the 

 holes at the near needle, which will be seen distinctly, 

 while the far needle will be double, both images 

 being somewhat dim. 



(3) With another card, while accommodating for the 

 near needle, close the right-hand hole, the right-hand 

 image disappears; and if the left hand hole be closed, 

 the left-hand image disappears. 



(4) Accommodate for the far needle, the near needle 

 appears double. Now close the right-hand hole, and 

 the left hand image disappears; and on closing the 

 left-hand hole, the right-hand image disappears. 

 [Practical Physiology Stirling.] 



(5) Explain the phenomena, drawing figures which show 

 just what must take place in the eye. 



*The miscellaneous experiments of Lesson XLIX have been taken 

 from Stirling's Practical Physiology. The author takes this place and 

 opportunity to acknowledge his indebtedness to Prof. Stirling. 



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