HUMAN EMBRYOLOGY AND MORPHOLOGY. 



solid and divided into anterior and posterior parts by a transverse 

 fissure (Fig. 17). 



The anterior part, as is shown in figure 18, becomes (a) the 

 olfactory bulb, (b) the olfactory peduncle or tract, (c) the trigonum 

 olfactorium, lying between the lateral and mesial roots into which 

 the tract divides, and (d) the area of Broca. The posterior part 

 of the olfactory lobe (B in Fig. 17) becomes (a) the grey matter 

 of the anterior perforated space, and (b) the gyrus subcallosus 

 or peduncles of the corpus callosum (Fig. 18). 



Termination of the Olfactory Tract. — As is shown in figure 

 18, the mesial root terminates in the supra-callosal gyrus and 

 fornix, while the lateral ends in the uncus of the hippocampal 

 convolution. Olfactory nerve fibres also terminate in the trigone 

 and area of Broca. To the parts derived from the olfactory 



gyrus 



l^m- eo 



sept, lucid.. 



striae longitud. 

 gyrus subcallos. 



supra-callosal 

 gyrus 



gyrus dentatus 



tract (B) 



mesial root 

 anterior perforated space 



uncus ^collateral fissure 



band of Giacomini 

 uncus 

 temp, incis. 



Fig. 18 -Showing the parts formed out of the Olfactory Lobe in the brain of an Adult 

 (After BlUot "mitlO olfilctol T Hoots in the Sub-callosal and Uncinate Gyri.' 



lobe together with the uncus, the fascia dentata, the supra-callosal 

 gyrus, the fimbria, the fornix and septum lucidum (Figs. 18 and 

 172) the term Rhinencephalon is given because these" parts are 

 concerned with the sense of smell, and represent the parts first 

 and most highly developed in the brains of lower vertebrates 



