The =sinus temporo-sphenoideus= (Fig. 62, No. _A_, 5) extends forward and outward from the transverse sinus, and, between the corpus quadrigeminum and the cerebrum, unites with the sinus venosus annularis basilaris. The =sinus venosus annularis basilaris= lies in the region of the optic nerve and surrounds the hypophysis, forming a complete circle. It receives small vessels from the cerebrum, the corpora quadrigemina, and anteriorly the longitudinal basilar vein or vena basilaris media, of the cerebrum, which comes out of the anterior annular venous sinus. The anterior annular venous sinus surrounds the base of the olfactory nerves. It communicates with the sinus petrosus sphenoideus, which emerges from behind the optic lobe, the sinus temporo-sphenoideus, which emerges from in front of the optic lobe, and posteriorly the median longitudinal vein of the medulla oblongata or vena basilaris. Laterally and anterior to the optic lobe it receives the vena basilaris lateralis, and also a branch of the vena ophthalmica. The blood received by the =sinus annularis basilaris= comes from the brain cavity through three pairs of veins, as follows: first, the two ophthalmic veins which pass through the posterior orbital wall between the olfactory and the optic nerve; second, two other branches of the ophthalmica which pass with the optic nerve; third, two veins which pass through a foramen by the side of the sella turcica to the hypophysis together with the carotis cerebralis, and then leave the cerebral cavity ventrally, at which point they are called the venæ carotes. These last accompany the cerebral artery backward, and pass through a foramen in the base of the cranium. Each one then passes through the cranial wall close to the external auditory canal, and empties into another vein in the posterior region of the head. The =sinus fovæ hemispherii cerebelli= lies in the hollow between the os petrosum and the semicircular canals. It receives blood from the external occipital sinus and from the cerebellum, and empties into the vena auris interna. VEINS OF THE BRAIN CAVITY The =vena auris interna= passes through a bony canal along the outer rim of the posterior semicircular canal and then along the external semicircular canal. It receives vessels from the labyrinth, and extends along the posterior rim of the tympanum to the outer ear canal. The =vena occipitalis interna=, extending from the sinus foraminis occipitalis, passes through the side of the atlas and divides near the condyle into two branches. One of these branches the internal occipital, forms the root of the vena vertebralis, and the other empties into the vena occipitalis externa. Near the outer and upper part of the condyle it forms two large veins and collects the blood from the vena occipitalis media. These veins collect the blood from the rectus capitis anticus, and communicate with the vena cephalica anterior.