NATURAL SUBDIVISION OF THE CEREBRAL HEMISPHERE. 443 



be HO doubt that the depression he refers to in the embryonic 

 human brain as the ''fissura rhinica" of Turner (o/>. cit., "die Anat. 

 Nomenclature' p. 176) is not the true rhinal fissure. For Eetzius 

 has clearly shown {Das Menschcnhirn, 1896) that the rhinal 

 fissure in the early human fcetus is exactly analogous to that 

 of other mammals, and cuts into the temporal region [witness 

 the incisura temporalis of the adult] instead of marking the 

 cephalic limit of the temporal pole. In other words, the rhinal 

 fissure marks off a part of the temporal pole which belongs 

 to the pyriform lobe. 



Sir William Turner approached the consideration of this 

 subject from the comparative standpoint, and therefore avoided 

 the error regarding the pyriform lobe which His committed, 

 and still persists in committing, although apparently uncon- 

 sciously and unintentionally. Turner, therefore, includes in 

 his " rhinencephalon " the whole, and not merely the anterior 

 part, of the pyriform lobe. It " consists," to use his own 

 words, " of an olfactory bulb, a crus or peduncle, and a lobu.s 

 hippocampi "(" The Convolutions of the 'Evdihi," Jour, of Anat. 

 and Phys., vol. xxv., 1890, p. 107). He says nothing concerning 

 the gyrus subcallosus, Broca's " carrefour," or the septum 

 lucidum, so that presumably these structures are excluded 

 from the " rhinencephalon," which means that they form part 

 of the " pallium." 



By this not unnatural process of extending Owen's term 

 to include not only the olfactory bulb but also its obvious 

 appendage, so to speak, the pyriform lobe, Turner has inci- 

 dentally introduced a paradoxical nomenclature. The terms 

 " pallium " and " rhinencephalon " are now used as comple- 

 mentary expressions, so that the pyriform lobe, being regarded 

 as rhinencephalic, cannot be " pallium " ; and yet the posterior 

 portion of this " lobe " fulfils all the conditions which had 

 hitherto been regarded as distinctive of pallium or mantle ; 

 in other words, it is a complex or cortex and medullary layer 

 quite free from the corpus striatum {vide fig. 5). In the strict 

 meaning of the term, the poster ior part of the pyriform lobe is 

 " pallium " in the sense of Reichert. 



The genesis of such a conception of a rhinencephalon may 

 be indirectly attributed to Broca's suggestion of a "limbic 



