Previous experiments in dogs demonstrated that the fever in experimental atelectasis was caused by sympathetic vasoconstriction stimulated by bacterial infection in the collapsed segment.1 The tachycardia was also of sympathetic origin, while the tachypnea was caused partly by bacterial infection and partly by the associated decreased arterial oxygen saturation and decreased lung volume. Certain questions remained to be answered, however. These included the importance of species variation; the role of inadvertant bronchial contamination at the time of plug insertion; and the effect of prolonged antibiotic administration on the bacterial flora in the atelectatic segment. The earlier bacteriological studies in dogs have been extended and observations in cats and humans added in an attempt to answer these problems.
The experimental animals were devocalized mongrel dogs of both sexes weighing 20 to 40 lb and cats of both sexes weighing 5 to 12 lb. Anesthesia was induced with hexobarbital, 15