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Systemic blood flow distribution was monitored in a variety of anuran amphibians using trapping of 54-pm mean radionuclidelabeled micre spheres during control, dehydration, hypovolemia, and salt load treatments. The head was the only region which showed significant increases in its proportion of systemic blood distribution in both dehydration and hypovolemia relative to controls. Proportionate declines in blood flow were observed to skeletal muscle regions during dehydration and hypovolemia. Salt loading had no effect on blood flow distribution. The redistribution results are consistent with sympathetic reflex control during hypovolemia and dehydration. The magnitude of the cerebral redistribution did not correlate with a species' tolerance to dehydration.

A description of the use of the Keller method of instruction in a general physics class of 100 students is presented. This teaching technique is critically evaluated by comparing the performance of the students in the program with that of 100 students in a concurrent control group run by the traditional lecture method. It is found that performances are not significantly different and the cost of running the program is not excessive. Furthermore, student reaction to the program is found to be quite favorable.

Volume phase holograms in a n electrooptic crystal like LiNbO, must be fixed so that they are not destroyed upon reading. By heating up the crystal mobilized ions may partially eompensetc the electronic space charge field, and a subsequent development procedure fixes the hologram. A general theory of this t'hermal fixing process is developed and applied to ZiNb0,:Cu. Charge transport by the photovoltaic effect, by drift in a space charge field and by diffusion is taken into account. It is unlikely that mobile protons alone are responsible for the fixing effect. Volumenphasenhologramme in einem elektrooptischen Kristall wie LiNbO, miissen fixiert werden, so daR sie nach dem Lesen nicht zerstort werden. Die durch Aufheizen der Kristalle mobilisierten lonen konnen partiell das elektronische Raumladungsfeld kompensieren und ein darauffolgendes Entwicklungsverfahren fixiert das Hologramm. Eine allgemeinc Theorie dieses thermischen Fixierungsprozesses wird aufgestellt und auf LiNbO,: Cu angewendet. Ladungstransport durch den pliotovoltaischen Effekt, durch Drift in einem Raumladungsfeld und durch Diffusion werden berucksichtigt. Es ist unwahrscheinlich, da13 bewegliche Protonen allein fur den Fixierungseffekt verantwortlich sind.

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