The system of brahmacarya has been current since the birth of Brahma. A section of the population, especially male, did not marry at all. Instead of allowing their semen to be driven downwards, they used to lift the semen up to the brain. They are called urdhva-retasah, those who lift up. Semen is so important that if, by the yogic process, one can lift the semen up to the brain, he can perform wonderful workones memory is enabled to act very swiftly, and the duration of life is increased. Yogis can thus perform all kinds of austerity with steadiness and be elevated to the highest perfectional stage, even to the spiritual world. Vivid examples of brahmacaris who accepted this principle of life are the four sages Sanaka, Sanandana, Sanatana and Sanat-kumara, as well as Narada and others.   (More...)

The word urdhva-retasah in this verse is very significant. Urdhva-retah refers to one who can control sex life and who instead of wasting semen by discharging it, can use this most important substance accumulated in the body to enrich the brain. One who can completely control sex life is able to work wonderfully with his brain, especially in remembering. Thus students who simply hear Vedic instructions once from their teacher could remember them verbatim without needing to read books, which therefore did not exist in former times.   (More...)