Sri Aurobindo
Letters of Sri Aurobindo
Volume IV - Part 3
The most recent discovery about the sex is that the liquid is composed of two elements – one is used for sexual purposes, the other supplies all kinds of higher energies, vital, mental and, I would add, spiritual. It was formerly supposed by the doctors that the sex-liquid had to be spent in order to relieve its excess from time to time, otherwise there would be bad results. It is now found that that is not necessary – if the sex is controlled both in 
act and thought, there is an automatic diminution of the amount of liquid used for sex and a corresponding increase of the other element available for higher energies. In other words, the old knowledge of the Vedic and Vedantic Yogis and Rishis about becoming urdhwaretaḥ, viz. that by control one can turn retas into ojas and use it for higher energies vital, mental and spiritual is amply justified by this discovery. The use made naturally depends upon a man’s occupations and interests. The athlete etc. would use it for physical strength and its work, the poet and artist for creation, others for study or mental work of different kinds, the Yogi for the increase and use of spiritual energy.