Herrick, Subdivision of the Brain. 405 



in the phylogeny to the rostral end of the original neural tube. 

 The BNA has done well to omit from it the pars optica hypothal- 

 ami which was originally tabulated as part of this region by Pro- 

 fessor His. Originally developed as primary and secondary olfac- 

 tory centers, it has added successively more and more complexity 

 during the whole course of phylogenetic history. 



The most ancient, or stem portion of the telencephalon we may 

 term, following Edinger,^ the hyposphaerium, and the dorsal cor- 

 relation centers episphaerium. The term rhinencephalon may 

 properly be applied to the whole of the primary olfactory brain, 

 including the olfactory bulbs, tracts and basal centers and also 

 the anterior commissure and lamina terminalis. The only im- 

 portant structure of the mammalian hyposphaerium not included 

 in the rhinencephalon is the corpus striatum. The episphaerium 

 is subdivided after Elliot Smith into archipallium and neopal- 

 lium, the former including the olfactory cortex (hippocampus, etc.) 

 and the fornix, the latter including the more recently developed 

 cortical representation of the other senses and their association 

 centers and the corpus callosum. Our subdivision of the telen- 

 cephalon, then, is as follows: 



Hyposphcsriiun : 



Rhinencephalon (inch lamina terminalis, ant. com. etc.) 

 Corpus striatum. 



Episphcerium: 



Archipallium (including fornix). 

 Neopallium (including corpus callosum). 



The confusion in the nomenclature of the forebrain is so great 

 that one hesitates to recommend any of the old terms, for all have 

 been used with diverse significations, and that too very often by 

 authors who supposed they were using them similarly. The BNA 

 terms seem to have suffered especially from this latter form of 

 misuse. Yet one shrinks from adding to the burden by coining 

 new terms which would be free from these confusing impHcations. 

 The best course is to select the most fit of the current terms and 

 try to give them precision by accurate definition. One of the 

 most valuable contributions in this direction is that of Elliot 



' Edinger, L. Ueber die Herkunft des Hirnmantels in der Tierreihe. Berliner klin. Wochenschr., 

 1905, no. 43. 



