INFLUENCE OF AGE AND WEIGHT OF PIGS ON RESPONSE TO SODIUM EVIPAN

Young pigs (large white breed) are favourable subjects on which to study the relation between dosage and body weight because they weigh about 1 kgm. at birth and rise to 80 kgm. within 6 months. The range of weight is similar to that which covers the growth of human beings. The experiments described below were made to determine firstly the susceptibility to a quick-acting barbiturate of new-born pigs and secondly the relation between dosage and body weight. The former point is. of practical in-terest in relation to the use of barbiturates in obstetrics and the latter point is of importance as regards basal narcosis in children. The literature relating to barbiturates is too extensive to per-mit full references, but comprehensive reviews have been com-piled by Lundy (1) and by Levy (2). The following special points are relevant to our experiments. Holck et al. (3) showed that adult male rats were more resistant than female rats to quick-acting barbiturates, but showed no sex difference in response to slow acting barbiturates. No sex difference was found with other animals (dog, cat, rabbit, guinea pig). Tolerance to repeated administration of pentobarbital was noted by Moir (4) and Carmichael and Posey (5). No sex difference was observed in the young pigs and we endeavoured to avoid establishment of tolerance by allowing at least 7 days ’ interval between injections. As regards the relation between dosage and body weight in adult animals Mulinos (6) using amytal on cats found that large animals were more resistant than small ones. Bazett and Erb (7) found the reverse to be true of pentobarbital given to cats an