DEFINITIONS. If it is assumed that the effect of
illumination on the rate of deterioration is superposed
onto the deterioration in darkness, the dose-effect
relationship can be measured by the difference between
the parameter values of the control in darkness and the
sample under illumination, both at the same moment of
time. In the range of intensities and times of exposure
numbars of normally moving spermatozoa and migration
rates did not deviate from an exponential decrease with
time, n(t)= n_.exp -kt , whereas decrease of the mean
velocity was Still in the straight-line region (2).

Accordingly, the biological effect of illumination
may be measured by y(I) - y(I=0) .t , where y
represents a rate constant, either k§ = -d(1n N)/dt,

k. = -d(ln Nv)/dt, or -dv/dt. This Type of expression
ng used instead of the simple ratio of the rate con-
stants y(I)/y(I=0), because for testing the reciprocity
law it is required to have the effect expressed in
relation to both I and t.

If the reciprocity law holds, the biological effect
ghould be linearly proportional to the product I.t and
a plot of log (I.t) vs. log I values required to obtain
a constant effect should show a horizontal straight
line (5).

RESULTS. Figs. 1-2 represent the outcome with as the
parameters the numbers of normally moving spermatozoa
and their mean velocities, respectively, demonstrating
that the hypothesis of validity of the reciprocity law
must be rejected. With respect to the migration rate
N.V as the parameter, results were similar. 15

In the intensity region below 7000 lux for N and N.v,
and below 2500 lux for Vv, increasing illumination
intensity had a smaller effect on deterioration of bull
spermatozoa than predicted by the reciprocity law,
meaning that if, for instance, within this region the
intensity is doubled, the required time of exposure for
obtaining the same effect will be more thar the expect-
ed half of the preceding value. Apparently in this
region the efficiency of the absorbed photons decreases
with increasing flux ratio.

The curves for v and NV (the latter not shown here)
indicate that at higher intensities than 2500 and 7000
lux, respectively, after a short region where there is
reasonable aequivalence of variation of intensity and
time of exposure, the efficiency of the absorbed
photons increases, thus reversing the direction of the
deviation from the reciprocity law.

 

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