THE HYPOTHALAMUS AS A THERMOSTAT REGULATING BODY TEMPERATURE*

THE REMARKABLY STABLE BODY TEMPERATURE of warm blooded animals is evidence of an efficient thermostatic control. Heat is continuously formed in the body even during rest and the amount thus formed is very greatly increased by muscular activity. To maintain ar even temperature the rate of heat loss must be adjusted to the rate of heat formation and this adjustment is complicated by changing environmental temperature. A high external temperature reduces heat elimination, and vigorous muscular exercise increases heat production, causing the body temperature to rise and thus starting heat loss activities such as dilatation of the cutaneous blood vessels and sweating. Jn carnivores panting is the chief means of heat elimination. Exposure to cold causes shivering, which increases heat production, and constriction of the cutaneous vessels which reduces heat loss by diminishing the flow of warm blood to the skin.