. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 416 Comparative Animal Physiology The several products resulting from the bleaching of rhodopsin, , vis- ual yellow and visual white, indicate that the kinetics of the production of rhodopsin is not as simple as was originally formulated by Hecht (page 408). Instead of a single reaction, there are now known to be three reactions involved in the synthesis (Fig. 119). This complexity of the reaction is in evidence if a series of dark-adaptation curves obtained from one photore- ceptor, as in Figure 124, are co
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 416 Comparative Animal Physiology The several products resulting from the bleaching of rhodopsin, , vis- ual yellow and visual white, indicate that the kinetics of the production of rhodopsin is not as simple as was originally formulated by Hecht (page 408). Instead of a single reaction, there are now known to be three reactions involved in the synthesis (Fig. 119). This complexity of the reaction is in evidence if a series of dark-adaptation curves obtained from one photore- ceptor, as in Figure 124, are compared. The curve of recovery after adapta- tion to a low intensity of illumination, , 4 millilamberts, is quite different from that of recovery after adaptation to high intensity of illumination, , 4700 millilamberts. Recovery curves obtained after intermediate intensities of illumination form a graded series between the two extremes. Jahn^'^ dem- onstrated these differences by plotting the data as shown in Figure 124, rather than in the conventional log of threshold intensity-time plot used by most workers. 1. Fig. 124. Curves showing the progress and extent of dark adaptation after exposure to Hghts of different intensity. Data from a normal human subject. The ordinate repre- sents the reciprocal of threshold intensity, the abscissa represents time (minutes) in the dark. The numbers on the curves indicate the intensity (millilamberts) of the adapting light. From Jahn.*° Inspection of this series of curves (Fig. 124) revealed that the data for the lowest adapting intensity could be fitted best by the equation for a mono- molecular reaction (p. 407), whereas the curve for the highest adapting intensity could be fitted with the equation for a monomolecular auto- catalytic equation. The intermediate curves could not be fitted by either of these two equations. Jahn^" proposed an equation relating the increase of rhodopsin (Z) with respect to time in the dark (t), 1
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