n. The fore-brain; the cerebral hemispheres, together with the callosum, striate bodies, and fornix. It may also include the rhinencephalon.n. All of the parts developed from the anterior of the three primary cerebral vesicles, including, in addition to those of , the thalamencephalon. Also called procerebrum.n. The second cranial segment, counting from before backward, of the four of which the head has been theoretically assumed to be composed. See cuts under encephalon and Petromyzontidæ.