The author considers of atmost importance the anatomical arterial-venous conjugate, represented by the internal carotid artery and the cavernous sinus, as well as the carotid venous plexus which covers the internal carotid artery within the petrous portion of the temporal bone. He believes that besides protecting the vascular arterial wall in acute episodes of hypertension, it can also contribute to the mechanism of the carotid blood flow. This is due to the fact that he considers the physiological conditions of the cavernous sinus in relation to the others dural venous sinuses and the endocranial venous system and its cavernous constitution, which differs from other venous blood canals with their own venous physiology and different functions. He attempts to compare it to the rest of the body areas where cavernous plexuses are localized and where venous pressure reachs high proportions, in comparison with the other regions without this morphologic constitution. He establishes a correlation resulting form the cerebro-vascular resistence mechanism, the participation of which he considers as differing from others dural sinuses and encephalic veins. He also emphasizes physiologically the carotid siphon and believes that it participates in the hemodynamics, when the patient is lying down (in a horizontal position) with hypotension, facilitating the blood access to the brain, thus avoiding consequent anoxia and decerebration, within certain limits, and constituting an additional mean of body defense.