( 336 ) 



The I'OgioJi al»(»\e llic iii\;i,L!,iiia!i(»ii ol' llio plexus is llic |»(»stori(»r 

 roof poi'lioii of' I he [)i'iinarv fore hi-aiji. IJoiow the iii\a,uiiialion of 

 the plexus lies Ihe lamina reujiieiis, llie lo^\ei' ])arl of" which eor- 

 responds 1o the lamina lerminalis of the adull animal. Hefore the 

 praeoptic recess we find on the basal inner snrface a shallow trans- 

 verse prominence, wliich is lalerallv ])rohin,<i,ed into the cenli-al mass 

 of the striated bod v. 



This transverse ridge of which even in llie median plane we can 

 recognise indications, coi-i-esponds to the ci-us melarhinicum corporis 

 striati of the hnman embryo, described by His ^). Conseqnently it 

 |»asses medially into the lamina lerminalis. Only in somewhat moi-e 

 laterally situated sagittal planes we meet before the cms metai-hinicnm 

 with a second transverse prominence, which sinks away into the 

 olfactory lobe. 1 designate it as ci-ns rhinicum corporis sti'iati. it 

 corres|)onds to the crns mesorhinicnm of the human embryo. A ci'ns 

 ej)irhinicum is scarcely indicated. In my opinion it is oidy connter- 

 feited by the fold of the latei-al I'hinal fissure. On the outer contour 

 we find corresjjonding to the l)ordcr of the cms metarhinicum and 

 I'hinicum a shall()\v groove, corres))onding ajiproximately to the 

 posterioi- edge of the cappa olfactoria and also approximately to tiie 

 anterioi- Q(\gQ of the olfactory tubercle. It i)y no means corres))onds 

 exclusixely, as His seems to assume, during its whole course to the 

 cms rhinicum or mesorhinicnm. I believe that its formation is essen- 

 tially independent of the morphological condition of the striated cor|)us 

 and has rather to be explained by thickening of the wall of the 

 olfactory lobe by supei'positi<tii of the olfactory ganglion (capi)a 

 olfactoria) on one hand and of the olfactory tubercle"^) on the other. 

 To this is added a shar|) bend in the brain tube iu a basal 

 direction when it |)asses from the hemisphere to \\\o olfacloi-y lol)e. 

 Moreover we must beai- in mind that the lumen of the ventricle, 

 when passing from the hemisphere to the olfactory lobe, at first 

 tapers very ra])idly, but then again very slowly ■'). Es|)ecially at the 

 base this behaviour is very conspicuous. Obviously this must result, 

 quite independently of a thickening of the wall by the striated 

 corpus, in a basal transverse groove. The designation "fissura meso- 

 rhinica" which His has given to this latter, does not seem to me 

 appropriate under these conditions. I pro])Ose to sj)eak of a lut/I/s 

 mcsorhinica. A second transverse groove is found caudalh of the 



1) Hip, Die lvat\vickelui:g des mensrhlichen Geliirns wiilu'end lU'v ersloii Monale. 

 Leipzig, S. Hirzel, 1904. S. (11 (cf. also fig. 34-, p. 50). 



") Tlie two lioidei'S only (^liiicide l)y (•liance and not accurately. 



^) Die EuLwickeluiig des uienschl. Geliirns etc. Leipzig 1904, p. 54 and p. ÜO. 



