What the body does to try to survive extreme cold is, in its own way, as remarkable as the outcome it produces when it succeeds.

The physiological response to severe cold is, at its most fundamental level, a triage system.

The body cannot maintain adequate blood flow and warmth to all its tissues when core heat production is insufficient to compensate for surface heat loss.

So it makes choices — not conscious choices, but the choices built into millions of years of evolutionary programming.

Blood is redirected from the periphery to the core.

The skin and the muscles of the arms and legs receive progressively less blood, because their function — movement, sensation, the cosmetic and social functions of human bodies — is less critical to immediate survival than the function of the heart, lungs, liver, and kidneys.