NATURAL SUBDIVISION OF THE CEREBRAL HEMISPHERE. 441 



of the cerebral surface. He also includes in his " olfactory lobe " 

 the so-called " outer root of the olfactory nerve." Now, if this 

 so-called " root " in the human brain be compared with that of 

 a macrosmatic mammal, or even with the condition found in the 

 early human embryo,^ it will be found to consist of the cephalic 

 extremity of the pyriform lobe upon which the olfactory tract is 

 spread as its superficial medullary layer. A " lobe " of the 

 brain cannot be partly formed of a layer of nerve fibres without 

 also including the cortical area of which this layer forms an 

 integral constituent.- Now, if the anterior part of the pyriform 

 lobe be included in the " Eiechlappen," there can be no legiti- 

 mate reason (provided, of course, that the lobe is to be a natural 

 division) for excluding its posterior part — the so-called "hippo- 

 campal lobule." 



Upon these grounds alone His's suggestions will not stand 

 the test of comparative anatomy, because they introduce purely 

 arbitrary lines of demarcation between regions which, in a 

 natural classification of cerebral areas, should not be sepa- 

 rated. 



The German Anatomical Nomenclature Commission adopted 

 the teaching of His in this matter in its entirety, and called his 

 " lobus olfactorius " the " rhinencephalon," under the mistaken 

 idea that it represented the region so-called by Turner.^ 



As His adopts the subdivision of the surface-areas of the 

 hemisphere into pallium and rhinencephalon, and excludes from 

 the latter the septum lucidum, the posterior part of the pyri- 

 form lobe, and the whole hippocampal formation, it, of necessity, 

 follows that these regions form constituent parts of his 

 " pallium." His statements concerning the subdivision of the 

 mesial surface of the hemisphere are, however, too vague to 

 indicate this peculiar grouping of surface-areas in a specific 

 manner; nor in his list of terms does he include either Broca's 

 " limbic lobe " nor Schwalbe's " falciform lobe " ; nor, again, does 

 he define the mesial limits of the frontal and parietal lobes of 



1 See G, Retzius, MriisrheuJiirn, 1896. 



- Moreover, His states that liis " olfactory lobe " includes the pyriform lobe. 

 Vide iiifrtc. 



^ W, His, "Die Anatomisclie Nomenclatur," Arch./. Anat. u, Phys., 1895, 

 Suppl. Bd., pp. 174-176, note especially the footnote v. on p. 174, in which 

 His says that he is using the terms in the same sense as Turner. 



