Intracellular injections of Lucifer Yellow into CA1 pyramidal cells of the in vitro guinea pig hippocampal slice enabled us to examine in detail the morphology of the axons of these neurons. We also recorded the electrophysiological responses of these neurons to alvear stimulation. In our morphological examinations, we found that many axons bifurcate in the alveus, with the major branch projecting caudally toward the subiculum and the second, thinner branch projecting rostrally toward the

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... a. Either axon may bifurcate further to produce several axon branches which follow parallel paths in the alveus. These axons also have local collaterals which project into strata oriens and pyramidale.