Newborn rabbits show behavioral and physiological thermoregulatory responses within the first hours of life. Although the mother prepares a nest for her young, she does not stay with them. The hairless immature young survive by huddling together in the nest. In this study, ambient temperature had a powerful influence on the behavior of newborn rabbits, and, providing they were warm, they did not huddle. The rabbits were studied over the first 10 days of life during which time their fur grows rapidly and their body weight nearly trebles. As each day passed, their preferred environmental temperature fell. In these observations smell and contact with littermates did not appear to have a major effect.

The preferred environmental temperature (T_E) and rates of oxygen consumption (VO₂) around the thermal neutral range were measured in rabbits on the day of birth and 2, 7 and 14 days after birth. On day 0, the preferred TE was 38.0 ± 0.8 °C, and it fell to 30.4 ± 0.5 °C by day 14. Day-0 rabbits kept for 1 h in a warm (41 °C), neutral (39 °C) or cool (28 °C) environment selected a different TE at 39.8, 39.5 and 37.3 °C, giving colonic temperatures (T_c) of 40.8, 39.9 and 37.7 °C, respectively. A similar phenomenon occurred on day 2, but not on day 7. It was concluded that newborn rabbits select a TE to match that which they experienced in utero and that this preferred TE changes after birth depending on the temperature of their surroundings and the development of their thermoregulatory control.

Calorimetric measurements have been made a t 20" and a t an ionic strength of 0.1 of the heats of formation of the 1 : 1 complexes of nitrilotriacetic acid with the bivalent cations of manganese, cobalt, nickel, copper, zinc, calcium, and strontium. For copper, the heat of formation of the 1 : 2 complex has also been determined. The heats of formation are small and do not vary much from one metal to another, the considerable variation in stability of the complexes depending more on differences in entropies of formation than on differences in heats of formation. The 1 : 1 copper complex has a particularly high entropy of formation, and perhaps in this complex, the metal ion only uses three of the four-co-ordinating centres of the nitrilotriacetic acid.

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