. The Journal of comparative neurology and psychology. the central gray and a number of nuclei of diverse func-tions. The fact that it must include the medial geniculate body onthe lateral surface of the diencephalon seems to the Avriter a fatalobjection to the tenn medithalamus. In the diencephalon the epithalamus and hypothalamus are fairlyclearly marked both functionally and morphologically. The hypo- 530 Journal of Comparative Neurology and Psychology. thalamus requires new definition both toward the thalamus and towardthe telencephalon. The latter is furnished in the new facts broughtout
. The Journal of comparative neurology and psychology. the central gray and a number of nuclei of diverse func-tions. The fact that it must include the medial geniculate body onthe lateral surface of the diencephalon seems to the Avriter a fatalobjection to the tenn medithalamus. In the diencephalon the epithalamus and hypothalamus are fairlyclearly marked both functionally and morphologically. The hypo- 530 Journal of Comparative Neurology and Psychology. thalamus requires new definition both toward the thalamus and towardthe telencephalon. The latter is furnished in the new facts broughtout in this paper; the proper boundary between thalamus andhypothalamus can be determined only after we have fuller knowledgeof the internal structure. The metathalamus and thalamus each pre-sents morphological unity and cannot well be improved upon atpresent. The chief changes needed in the BISTA at present are suchas are required by the new facts regarding the telencephalon and theboundary between it and the diencephalon. These will be Fig. 45. A, transverse section of the telencephalon of Petroiuyzon. Transverse Section of the Telencephalon.—A true transverse sec-tion of any part of the central neiwous system must cut across bothdorsal and ventral zones of the neural tube and must cut roof plateand floor plate as nearly as possible at the same antero-posteriorlevel. A little reflection will show that while such a section is readilyobtained in any of the lower segments of the brain and cord, a truetransverse section is seldom cut in the telencephalon. Such a section Johnston, Forehrain Vesicle in Vertebrates. 531
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