This vesicle becomes, we cannot doubt, the vesicle on the roof of the thalamencephalon which we have described in the adult brain.
The fore-brain consists (fig. 43) of a thalamencephalon (th) and an undivided cerebral rudiment (ch).
The anterior wall of the thalamencephalon as well as its roof are very thin.
To the roof of the thalamencephalon is attached a flattened sack (pn) which is probably the pineal gland.
In the thalamencephalon there is no fresh point of great importance to be noticed.
It arises (fig. 253 pn) as a sack-like diverticulum of the thalamencephalon extending at first both backwards and forwards.
During the same stage the pineal gland grows into a sack-like body, springing from the roof of the thalamencephalon, fig. 1b, pn.
The proximal extremity attached to the roof of the thalamencephalon forms a special section, known as the infra-pineal process.
The floor of the thalamencephalon projects downwards and backwards as the infundibulum.
The optic chiasma, where present, is involved in the floor of the thalamencephalon and forms a large, upwardly-projecting ridge.
thalamencephalon thal·a·men·ceph·a·lon (thāl'ə-měn-sěf'ə-lŏn')
The part of the diencephalon comprising the thalamus and its associated structures.