Journal officiel de l'ophtalmologie, l'otologie et de laryngologie . continue lentement jusqu'à un équilibre estaccessible. La durée de la rétine pour atteindre un état de com-équilibre complet est plutôt discutable, et quelques observershave ont continué l'expérience pendant plusieurs heures. En tout état de 621 Prentice Reeves. application on peut supposer que l'équilibre a été atteint après 30 minutes (au plus une heure) que les mesures du seuil de l'areabout la même après que le temps pour toute la luminosité initiale sensibiliser.Un fait intéressant dans le taux de croissance de la sensibilité avec adaptationis l'effe

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Journal of ophthalmology, otology and laryngology . continues slowly until an equilibrium isreached. The length of time for the retina to reach a state of com-plete equilibrium is rather a debatable question, and some observershave continued the experiment for several hours. For all practical 621 Prentice Reeves. purposes we may assume that the equilibrium has been reached after30 minutes (at the most an hour) as the threshold measurements areabout the same after that time for any initial sensitizing brightness.An interesting fact in the rate of growth of sensibility with adaptationis the effect of the color of light used. The adaptation is least andmost slowly for red, then come yellow, white, green and blue. Thesensibility change in blue light proceeds much more rapidly and muchfurther than in red light. Not much data have been obtained foradaptation when changing from darkness to light, although we knowthat the rate of adaptation from lower to higher intensities is morerapid than the rate from higher to lower. A person gets his eyes. Fiq. l-Jisual densitometer. quicker when turning on a light in a darkened room than when turn-ing off the light in a lighted room. In any process of adapta-tion there are two factors, the retinal process, whatever it is, andthe change in the pupil opening. We have examined the former, now let us consider the latter. The pupil has been found to varythrough a wide range and series of photographs have been takenof the eyes of several subjects over the entire brightness range.The subject was adapted to the desired brightness level for atleast five minutes and a photograph taken of the eye. For dark-ness and faint intensities instantaneous flashlights were taken, whileordinary exposures were made for the higher intensities. By takingthe photographs through the same brightness range that was used inthe sensibility experiments we can directly compare the pupillary range 622 The Effect of Various Physical Stimuli. with the sensibility range.

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