The Influence of the Occipito‐vertebral Anastomoses on the Carotid Sinus Reflex of the Sheep

It has been shown that in sheep the carotid sinus nerve innervates the artery at the origin of its occipital branch and that the carotid bodies are in the same region. Occlusion of the carotid arteries causes a fall in sinus pressure and a reflex rise in general blood pressure, but blood from the vertebral circulation flows through the occipital arteries and into the sinus region sufficiently rapidly to modify and reduce these effects. These are demonstrable in conscious sheep with exteriorized carotid arteries and so, to obtain reliable blood pressure records from an exteriorized carotid, it is necessary to denervate the sinus on the same side.