Henry Gray (18251861). Anatomy of the Human Body. 1918.
covered by the epithelial lining of this cavity; the medial part is covered by the tela chorioidea of the third ventricle, and is destitute of an epithelial covering. In front, the superior is separated from the medial surface by a salient margin, the tænia thalami, along which the epithelial lining of the third ventricle is reflected on to the under surface of the tela chorioidea. Behind, it is limited medially by a groove, the sulcus habenulæ, which intervenes between it and a small triangular area, termed the trigonum habenulæ.
The inferior surface rests upon and is continuous with the upward prolongation of the tegmentum (subthalamic tegmental region), in front of which it is related to the substantia innominata of Meynert.
The medial surface constitutes the upper part of the lateral wall of the third ventricle, and is connected to the corresponding surface of the opposite thalamus by a flattened gray band, the massa intermedia (middle or gray commissure). This mass averages about 1 cm. in its antero-posterior diameter: it sometimes consists of two parts and occasionally is absent. It contains nerve cells and nerve fibers; a few of the latter may cross the middle line, but most of them pass toward the middle line and then curve lateralward on the same side.
The lateral surface is in contact with a thick band of white substance which forms the occipital part of the internal capsule and separates the thalamus from the lentiform nucleus of the corpus striatum.