Scientists have for the first time witnessed Tibetan "heat meditation" rituals, previously hidden to western eyes, and have come back reporting that the ancient claims are true -- the monks can will their bodies to heat up, by as much as 15 degrees in less than an hour.

The yogis' ability shows how much mental control of body functions is possible--"far more than we thought before," said Herbert Benson, a researcher at the Harvard Medical School and Beth Israel Hospital, and the leader of the research team that went to India.

The six-man research team monitored vital signs and temperatures of three lamas, as the monks practiced the yoga meditation known as g Tum-mo (pronounced Two-mow), or "heat meditation." The meditation is part of a ritual in which the lamas produce heat in the body to burn away the emotional defilements that interfere with a proper outlook on life, Benson said.

Benson said that the Dalai Lama invited the scientists to India to study the meditation practices and some practices in Tibetan medicine, because the Dalai Lama said he feared that his Tibetan culture may be in danger of dying out.

The Chinese communists seized control of Tibet three decades ago. The Dalai Lama and other priests who ruled the country fled to India, where they now live in exile. One way now to save something of the Tibetan culture, the Dalai Lama has said, is to open up formerly secret practices of medicine and meditation to documentation and study, in the hope that some Tibetan skill and experience may be passed on to the world.

The small skin-temperature rises achieved in biofeedback or other meditation techniques have already been used to treat the symptoms of Raynaud's disease, an ailment characterized by involuntary cooling of the extremities to the point that sores sometimes develop. But the techniques of the lamas in heat meditiation are different and far more effective, Benson said.

Benson and his colleagues John Lehmann, M.S. Malhotra, Ralph Goldman, Jeffrey Hopkins and Mark Epstein reported the lama study in the Jan. 27 issue of the British journal Nature.

Small temperature-sensing wires were taped to the skin of the monks in a number of locations--the spine, calf, nipple, navel, palm, toe, and finger. Rectal temperature was also taken. Measurements were taken before meditation, during an hour's meditation, and then after it for half an hour.

The temperature deep in the body remained normal (near 98.6 degrees), while skin temperature of the lamas rose all over the body by two to three degrees.

But on the fingers and toes, the skin areas which are most easily affected by the body's temperature system, the numbers were more dramatic. The average temperature rise on the fingers was 10 degrees Fahrenheit. The average temperature rise on the toes was 11 degrees.

The biggest rise was a 15-degree rise in the skin temperature of the toes of one of the lamas.

These temperatures were all the more remarkable, Benson said, because they were taken in rather chilly rooms--between about 60 and 66 degrees. The body reacts to the cold normally by withdrawing circulation from the skin back into the body, so in a cold room one would expect skin temperature to drop a few degrees rather than rise.

The research team hopes to return to India to study some other physiological facets of Tibetan meditation, as well as other practices of Tibetan medicine.