810 



the nticli'iis latei'dlh .tepti is a conspioiioMs sinicture. Tlie nucleus 

 medudis septi is also visible. The zona g lio.sa limitans sepiivixies ihese 

 nuclei from the Area 28 of Rose (1914) which is well (lelined. The 

 medial limit of this zone is indicated by the jïssura septo-pallialis. 

 Oi) the ventricnlai- side of (he seplnm the lateral limit of the zone 

 is marked hy the JJs.nira Uviitnns hippocampi. Dorsal lo the Area 28 

 slight indentations laterallj' and medially serve to mark off this 

 area from the cortex. 



As the secondary olfactory fibres disappear posteriorly they are 

 replaced by a great fibre field which extends completely aci'oss the 

 ventral portion of the hemisphere. Fig. IV shows that the major 

 jioilion of the hemisphere in this region consists of the corpus 

 stiiatum (capynt hi/pen-triati). The fibres first become distinct on the 



Tt frep (p<l)^ 



ya\ 6 



Tr olf hob 



F.9V 



lateral surface of this structure but are soon seen to be arising 

 from the whole ventral region of the hemisphere extending to the 

 medial wall. When this extent has been attained (Fig. V), it becomes 

 obvious, as the connexions of the fibres also show, that there are 

 three main elements in this fibre field. 



The most medial bundle arises from the region of the area 

 praepirif()rniis and septum. It forms a conspicuous trad which 

 separates from the remaining fibres in order to enter the diencephalon 

 medial to the tractus seplo-mesencephahcus (Fig. VI). This tract is 

 the ventral forebrain bundle [basales Riechbiindel). In the diencephalon 

 it takes up its position lateral to the third ventricle (Fig. VIII) and 

 extends backwards as fai' as the nucleus ocidomotorius, (Fig. X). as 

 was shown by Jelgersma (1896). 



Lateral to the ventral forebrain bundle and ventral lo the main 

 field of fibres a secoiul conspicuous myelinated tract is to be seen. 

 It lies ventral to the base of the mesoslriatum and .so occupies a 

 superficial position (Fig. V). When the ventral forebrain bundle 

 enters the diencephalon it comes to lie more medially (Fig. VI), 



