Another female-male difference.

Another female/male differnce

The amount of blood flow to the hand is greater in men than in women, and the nerves controlling the flow are under tighter control in women, Mayo Clinic researchers in Rochester, Minn., have found. They were comparing blood flow in normal individuals in preparation for a study of people with Raynaud's disease, a benign condition marked by periods of low blood flow to the hands. Raynaud's disease is much more frequent in women than in men.

John P. Cooke and his colleagues measured hand blood flow, corrected for size differences and found that men had higher blood-flow levels. But after mental airthmetic or deep breathing to relax the automatic system that controls blood flow, the levels in women surpassed those in men. A naturally tighter control of the system could be related to the higher incidence of Raynaud's disease in women, Cooke suggests.