Maost guys continue to "leak" what is called pre-ejaculatory fluid, or cowpers fluid, both before and after ejaculation. The fluid is emitted during arousal, masturbation, foreplay or at an early stage during sex, some time before the man fully reaches orgasm and semen is ejaculated. It is primarily produced by the bulbourethral glands (Cowper's glands), with the glands of Littre (the mucus-secreting urethral glands) also contributing. The amount of fluid that the human male issues varies widely among individuals. Some men do not produce any pre-ejaculate fluid, while others emit as much as 5 milliliters (a little less than 2/10 of an ounce). Pre-ejaculate contains some chemicals associated with semen, such as acid phosphatase. Some semen markers, such as gamma-glutamyltransferase, are completely absent from pre-ejaculate fluid. Acidic environments are hostile to sperm. Pre-ejaculate neutralizes residual acidity in the urethra caused by urine, creating a more favorable environment for the passage of sperm. The vagina is normally acidic; the deposit of pre-ejaculate prior to the emission of semen may change the vaginal environment to promote sperm survival. Pre-ejaculate also acts as a lubricant during intercourse, and plays a role in semen coagulation. And semen, of course, is this fluid when it contains sperm, which make it look whitish.