An automatic bioassay for the identification of nerve trophic substances in a large number of organ cultures is being developed. BIBLIOGRAPHIC REFERENCES: Politoff, A.; A.L. Blitz and S. Rose: Incorporation of acetylcholinesterase into synaptic vesicles is associated with blockade of synaptic transmission. Nature 256:324-325, 1975. Politoff, A.: A simple stimulus isolation unit using a complementary metal oxide semiconductor switch. Experientia, 1975 (In press).