Retzius'* space, c. sep'ti pettu'cid i

[BNA], cavity of the septum pellucidum, fifth ventricle, a closed cavity, containing a little fluid, between the two laminsB forming the septum pellucidum it does not communicate with the other cerebral cavities, c. subarachnoid a'le, subarachnoid cavity or space, the interval between the a rach no idea and the pia mater; it varies in size, being practically nonexistent over the summits of the cerebral convolutions, but wider in the intervals, and is flUed with a mesh of loose fibrous ti ue and cerebrospinal fluid; it contains the larger branches of the blood ve els of the brain. The spinal subarachnoid space is wide and is divided into three compartments by the subarachnoid septum and the ligament a denticulata. b. subdura'le, subdural cavity or space, the very narrow interval between the dura mater and the arachnoid; contains only a small amount of fluid sufiicient to moisten the opposing surfaces of the two membranes, c. thora'cis, thoracic cavity, c. tym'pan i, cavity of the tympanum, tympanic cavity, middle ear; an air chamber in the temporal bone containing the o icles; it is divided into the atrium or tympanum, the lower part of the cavity lying to the inner side of the membrani tympani, and the rece us epitympanicus or attic, c. u'teri [BNA], uterine cavity, c. ves'ico-uteri'num, excavatio rec touter in a [BNA].