Studies on the nature of sweat gland 'fatigue' in the goat.

1. The nature of the ;fatigue' of sweating that occurs in the goat upon exposure to environmental conditions of 40 degrees C/26 degrees C (dry bulb/wet bulb) has been examined.2. Heat exposure activated all the sweat glands and the decrement in sweating which occurred was due to a decline in the amount of sweat produced by each gland.3. The decline in sweating activity was associated with a decrease in sweat gland volume and a thickening of the glandular wall. The restoration of sweat gland function took approximately 5-6 hr after removing the animal from the hot environment but the restoration of sweat gland volume took longer.4. The volume of sweat produced was greater than the decrease in sweat gland volume and it is concluded that ;fatigue' is due to the rate of expulsion exceeding the rate of sweat production.5. Repeated intravenous injections of adrenaline at 40 degrees C resulted in a decline in sweat output and reduced the normal glandular response to heat exposure.