928 



THE NERVE SYSTEM 



which connects them (the corpus callosum) has been an important factor in widely 

 displacing primitively connected parts. The developmental history must be 

 sought for in the writings of Edinger, Retzius, and Elliott Smith. 

 The Rhinencephalon comprises: 



1. Peripheral parts. 



2. Central or Cortical parts. 



A comprehensive term for the peripheral part is lobus olfactorius, divisible into 

 pre- and postolfactory parts. 



' 1 . Bulbus olfactorius. 



2. Tractus olfactorius, 



3. Tuberculum olfactorium and triyonum. 



4. Area parolf actor ia (Broca). 



5. Stria (gyrus) olfactorius medialis. 



6. Stria (gyrus) olfactorius inter medialis. 

 > 7. Stria (gyrus) olfactorius lateralis. 



Postolfactory lobe J s - ^nierwr perforated substance. 



\ 9. Gyrus subcallosus and Broca' s diagonal band. 



G. OLFACTORIO- 



ORBITALIS 



LATERAL STRIA 

 ANGULUS LATERALIS 



INTERMEDIATE STRIA 



ANTERIOR 



PERFORATED 

 SUBSTANCE 



GVRUS AMBIENS' 

 GYRUS SEMILUNARIS^ 

 FRF.NULUM GIAOOMIN 



J 

 UNCUS/ 



GYRUS SUBCALLOSUS 

 AREA PAROLFACTORIf. 



GYRUS OLFACTORIUS 

 MEDIALIS 



LIMEN INSULAE 



BROCA'S DIAGONAL 

 BAND 



LAMINA TERMi- 



NALIS 



8ULCUS SEMI- 

 ANNULARIS 



Fin. 680. ^Schematic representation of the rhinencephalon, basal aspect. 



THE PREOLFACTORY DIVISION. The olfactory bulb and tract form a long and 

 slender band with a bulbous extremity situated on the basal aspect of the frontal 

 lobe and constituting a rudimentary remnant of a relatively large diverticulum, 

 developed from the sensor ectoderm close to the border of the neural plate before 

 it becomes converted into the neural tube and situated on either side of the neu- 

 ropore at the extreme frontal end. Although hollow at first, the cavity (rhinocele) 

 soon becomes obliterated. 



The olfactory bulb (bulbus olfactorius} is an oval mass of reddish-gray color, 

 which rests on the cribriform plate of the ethmoid and is received in the olfactory 

 fissure on the orbital surface of the frontal lobe. It receives the numerous 



