The role of the dorsal nerves of the penis in the sexual behaviour of the male rhesus monkey

The effect of sectioning the dorsal nerves on the male monkey's sexual behaviour with oestrogen-treated females was examined in two experiments. In Experiment 1, first one and then both dorsal nerves were sectioned. In Experiment 2 progressively greater amounts of nerves were removed in a series of operations until none remained; the number of fibres removed at each operation was counted. Section of one dorsal nerve (Experiment 1) had no consistent effect on behaviour. Removal of more than half the total number of fibres caused ataxic thrusting and prolonged the time taken to ejaculation (Experiment 2). Total removal resulted in grossly abnormal thrusting and practically abolished ejaculation (Experiments 1 and 2). Intromission was less affected and continued to occur in the majority of mounts even after complete nerve section. Some males made an increased number of thrusts per intromission after partial nerve section, but markedly less when removal was complete. The mean mounting rate (i.e. the mean rate at which successive mounts occurred) was unaltered by partial section but decreased after total removal when overall levels of sexual activity declined; this occurred progressively after all the nerves had been removed. Pairing nerve-sectioned males, in which sexual activity had declined to low levels, with strange females could restore their sexual activity for a while. These results are compared with the effects on the male's behaviour of altering the hormonal condition of the female.