Fig. 5. We measured the rate of increase of the alveolar (F^A, end tidal) concentrations of halothane and four other gases toward the concentration inhaled (F^I) in five rats, four humans (ourselves), and one 7-ton California Gray whale named Gigi.38Trace concentrations of the gases were used (e.g. , 0.014% halothane.) The study tested and confirmed the notion that the rate of increase would be faster in smaller animals because ventilation and perfusion per kg would be greater. Gigi was released into the Pacific Ocean shortly after completion of the study and has not been seen since. Adapted from Anesthesiology 1974; 40:19-23.38