1881.] ^51 [Wilder. 



Fig. 5. — The cephalic aspect of the Prosencephalon after the removal of 

 the Lohi oJfactorii. From prep. 294. Enlarged two diameters. 



The hardened brain was transected at the FF. %)ostica, so that the prepa- 

 ration includes only the cephalic two-thirds of the prosencephalon. 



The drawing represents the preparation tilted up so as to expose the ven- 

 tral aspect foreshortened. 



As compared with fig. 6, this might well have been made of the natural 

 size. A less regularly symmetrical brain would have been more instructive. 

 One of the Crura olfactoria should have been divided at a little greater dis- 

 tance from the prosen. 



So far as appears in the figure, the fissures are remarkably alike upon 

 the two sides ; the left F. ansata {F. an.) however, only the meso-cephalic 

 end of which appears in the figure, presents the somewhat unusual but very 

 suggestive condition of entire independence of the F. lateralis (which is in- 

 visible) and the F. coronalis (F. cor.). On the right side it is joined by the 

 former fissure. 



The right F. syUiana (F. s.) is shorter than the left, and presents a 

 slight terminal bifurcation which is not shown. 



In consequence of the removal of the Lobi olfactorU, and the tilting of 

 the whole preparation, so much of the F. rhinalis (F. rli.) as lies cephalad 

 of its union with the F. superorMtalis {F. so.) is practically obliterated, and 

 the remainder of it is so foreshortened as to appear as an insignificant in- 

 termediate portion of an extensive u-shaped fissure formed by the FF. syl- 

 mana (F. s.) and superorbitaUs (F. so.). The appearances thus presented 

 are suggestive in view of the idea of Meynert (i, 12), which I also enter- 

 tained at one time (10, 225), that the F. superorbitaUs represents the "an- 

 terior branch" of the human F. sylciana, and that the intervening part of 

 the brain corresponds to the " operculum." 



A slight preponderance of the left hemisphere just caudad of the F. syl- 

 viana is somewhat exaggerated in the figure, and the Crura olfactoria 

 iCr. ol.) should differ less in form and in their distance from the meson. 



The FF. olfactories (F. ol.) appear as little more than shallow furrows. 



On account of the foreshortening of the ventral aspect, the line of sepa- 

 ration of the Portio prominens (Pt. p.) and'the Pt. depressa (jpt. d.) is indis- 

 tinct. The LI. hypocampm {LI. hmp.) on each side has been flattened by 

 pressure, and is so represented. 



Fig. 6. — The caudal aspect of tlie Prosencephalon, with part of the 

 Diencephalon, after the removal of the other parts of the brain. 



From prep. 292, an adult $ , 



The dien. has been transected so as to leave a concave surface which, at 

 the meson, is close to the caudal border of the medicommissura (mcs.), but 

 rises at the sides so as to coincide nearly with the caudal surface of the 

 prosencephalon. 



The postcommissura has been removed, and the slender transverse band 

 (Cs. h.). Just ventrad of the splenium (sp.) is the Commissura habenarum. 



