NEW MENSTRUAL THEORY

While I was reading the report on Margie Profet's ''radical theory,'' which proposes that menstruation protects against sperm-borne infection ((HEALTH, . Oct. 4)), an obvious hole came to mind. Human females may engage in sexual intercourse, and thereby expose themselves to potentially harmful micro- organisms, at any time during their menstrual cycle. If a woman were to have sex the day after her menstrual period ended, it would be another three weeks before her uterine lining was again sloughed off, which is more than enough time for an infection to set in. Because of this constant risk of exposure to disease, menstruation would have to occur much more often than once a month to be an effective defense against infection.

Lisa A. McKitrick Edmonds, Washington

Menstruation is the cry of a disappointed womb on a frustrated mission. Albert C. Cuetter El Paso, Texas

I think Profet is strongly influenced by modern human sex practices: women receiving sperm without getting pregnant. This very new behavior, in the biological time scale, will have to continue for tens of thousands of years before it affects natural selection. Dan Sandberg, M.D. Uppsala, Sweden