Response of the newborn rabbit to acute anoxia and variations due to narcotic agents.

Newborn rabbits were rendered acutely anoxic by insertion into an atmosphere of nitrogen and their respiratory movements were recorded by direct observation and by an impedance pneumograph. The respiratory response comprised periods of dyspnoea, preterminal apnoea, gasping, and terminal apnoea. The duration of preterminal apnoea was increased at the expense of the period of gasping by the prior administration of morphine or pethidine in a dosage insufficient to cause important respiratory depression in air, survival not being shortened.