On the direct and crossed components of reflex responses to unilateral stimulation of the carotid body chemoreceptors in the dog.

1. In dogs under chloralose-urethane anaesthesia the chemoreceptors of the two carotid bodies were separately stimulated.2. The distribution of three primary reflex responses to carotid body stimulation was studied: parasympathetic bradycardia, sympathetic vasoconstriction, and increase in somatic phrenic nerve activity.3. The reflex bradycardia evoked by either carotid body was mediated by both vagus nerves, but when either vagus was blocked a greater response could be obtained from the contralateral than from the ipsilateral carotid body.4. The reflex vasoconstriction evoked by either carotid body was seen in both hind limbs, with no predominance in either limb.5. The reflex increase in phrenic nerve activity evoked by either carotid body was seen in both phrenic nerves, with no predominance in either nerve.