Effects of temperature on P.S. in the pontile animal

The poikilothermic pontile animal is subject to changes in the environmental temperature, so that the effects of hypothermia on P.S. can be readily studied. The fall in rectal temperature occurring when the animal is placed in a cold environment causes P.S. to disappear almost entirely. If, however, cooling is stopped and the rectal temperature remains stable, P.S. reappears periodically. Its duration is then in inverse proportion to the rectal temperature (Fig. 22). An increase in the duration of P.S. during hypothermia goes hand in hand with an increase in the length of the intervals between each episode of P.S., the proportion of the latter always remaining in the region of 10%. We have observed periods of P.S. lasting 25 min at a rectal temperature of 29°. At this temperature the animals exhibit generalized clonism of the head and limbs, even when they are returned to a warm environment. There is no real shivering, however. During phases of P.S. clonism disappears almost completely. If the animal is rewarmed so that the rectal temperature increases P.S. occurs more frequently and in animals whose temperature rises from 30° to 37° in 4 h the amount of sleep can increase to up to 35% of the total time.

In contrast, we have never observed P.S. at temperatures above 40.5Ą. (This was the maximum temperature attempted, as hyperthermia has serious effects in pontile animals.)