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1. On the Action of Light on the Iris

Published online by Cambridge University Press:  15 September 2014

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Extract

Sect. I. It is well known that the movements of the iris are due to the stimulus of light, but I am not aware that any experiments have been hitherto made to determine the approximate quantity of that agent necessary to bring about this involuntary action. The usual way of observation precludes refined experimenting, it being customary to watch the iris of another person or animal whilst under the influence of varying amounts of light, or one's own iris by means of a mirror. Three methods will be described here, and I believe that one at least may afford a means of getting new data on this and other points.

Type
Proceedings 1878–79
Copyright
Copyright © Royal Society of Edinburgh 1880

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References

page 38 note * A simple method is here suggested for demonstrating to one's self the inverting action of the crystalline lens. With everything as here described, take a needle and bring it across the field of view close to the eyelids. If it move downwards, it appears to move upwards; if it be moved upwards, it appears to come downwards.