Fatigue of the sweat glands.

The rate of sweat secretion has been shown to decrease during prolonged exposure to heat (1-3). This phenomenon has practical importance in the etiology of heat stroke, since the evaporation of sweat is the only significant means for dissipating heat when the environmental temperature equals or exceeds the body temperature. It is not known whether this decrease in sweating rate is due to a failure of the sudomotor center or to an exhaustion of the peripheral glandular units. The present, investigation was undertaken in an attempt to answer this question. The' results indicate that the decrease in sweating rate is due primarily to fatigue of the secretory mechanism of the glands. Apparently sweating can continue indefinitely at the same rate only as long as the demand upon the secretory mechanism does not exceed the capacity of the simultaneous restorative processes. Whenever the demand upon the secretory mechanism exceeds restorative capacity the rate of sweating decreases.