a marked quickening of the respiration observed in many species of warmblooded, or homeothermic, animals when in danger of overheating. Such quickening may be caused by external temperatures, an increase in the body’s production of heat, or a combination of these factors. The accelerated breathing results in water evaporation and consequent heat loss in the upper respiratory tract and the oral cavity, as well as intensified blood circulation in the mucous membranes, and thus prevents the body’s temperature from rising.

The rate of respiration in thermopolypnea is very high. In dogs, for example, it may reach a frequency of 400 times per minute, with a fivefold or sixfold increase of blood circulation in the tongue and an eightfold to tenfold increase in the evaporation of water. Thermopolypnea results from the stimulation of specific thermoreceptors in the skin, the internal organs, and the thermo-sensitive nerve cells of the central nervous system. It is characteristic of many mammals, including predators, rodents, and artiodactyls. It is less marked in birds. Thermopolypnea should be distinguished from the moderate and gradual respiratory acceleration—common to all animals and to man—that accompanies increased body temperatures in certain pathological conditions.