[Impotentia coeundi and penile extension in steers].

Penis extension (emissio penis) depends on the length of the penis and on the relaxation of the retractor muscle of the penis. When the relaxation is insufficient, penis extension is at its smallest just before intromission takes place. In severe cases this can lead to impotence (impotentia coeundi). Whether this occurs depends on the animal's libido and mating behaviour and on external factors. Genetic factors play a role in emissio penis.