[Differentiation factors of active zones of presynaptic membranes].

The differentiation of the subsynaptic areas depends very probably on a local influence exerted by the axon terminals; but conversely, as suggested by obervations on the development of neuromuscular junctions of "fast" and "slow" muscle fibres in Anura, complementing the results of previous degeneration experiments on frog muscles, the subsynaptic areas might intervene in the differentiation of "active zones" of presynaptic membranes.