Differentiation and development of the male.

Male differentiation and development takes place against a tendency towards neutral or feminine differentiation. At each step of development male differentiation results from a suspension of a basic female development and the imposition of male features for which a normal functioning testis is necessary. Once the testis has differentiated early in gestation the establishment and maintenance of normal testicular function will condition male sexual differentiation and maturation. Nature likes to express herself in a rhythmic fashion (circhoral, ultradian, circadian, menstrual, long-term rhythms). To epitomise testicular function throughout development we would propose the term 'ontogenic rhythms' to describe the three periods of maximal testicular activity, fetal, neonatal and adult. This results in the differentiation which eventually determines adult sexual activity.