The clitoris lengthens and thickens, reaching maximum size. Just before orgasm, it pulls back behind the foreskin (hood).

The vagina dilates, the inner two-thirds widen and lengthen. The walls turn deep purple and are coated with lubricating fluid.

The labia outer lips open and flatten out. The inner lips thicken and thrust forwards.

The uterus balloons to almost twice its size. It rises and the cervix is pulled up away from the vagina.

The heart rate increases from an average 60 to 80 beats per minute to between 100 and 150.

The breathing rate becomes fast and shallow, and can speed up to 3 times its normal resting rate.

Muscle tension: The pelvis, abdomen, back and thighs contract and are held in a state of high tension.

Body language: The face can contort into a rictus, a glaring grimace; the hands may claw, the toes curl, the feet arch.

Mind: Mental faculties appear to be "gone," so deeply are they buried under orgasm's spell.

Sex rash: A rosy, measles-like rash starts at the throat and abdomen, then spreads to the breasts in 75 percent of women.

Sneezing: Attacks of sneezing, if they occur, are due to vaso-congestion in the nose.

Perspiration: One woman in three sweats on the forehead, the top lip, and underarm. A thin film may cover the back and thighs.