[The development of interrelationships between the activity-rest cycle and thermoregulation in rabbit fetuses]

The gradient of temperatures of the foetus and mother was found to increase along with an increase of the gestation age which coincides with an increase in the mass of grey fat tissue. In artificial placenta insufficiency, the activity-rest cycle of the foetuses is delayed by 1 or 2 days in their development. The mechanisms of thermoregulation were shown to start forming by 4 or 5 days earlier than the activity-rest cycle, the character of their functioning being comparable to that in poikilothermic animals.