THE OLFACTORY AND GUSTATORY AREAS. 



765 



arborise around the dendrons of the pyramidal cells, the axons of which also 

 then pass to the hippocampus to end in arborisations amongst the dendrons 

 of its pyramidal cells (Fig. 349). If this be so, both the gyrus subcallosus 

 and the fascia dentata are receptive areas of the second order for olfactory 

 impressions. 



Broca * was of opinion that the whole of the limbic lobe (consisting of 

 olfactory lobe, hippocampal lobe, and lobe of the corpus callosum) is related to 

 the sense of smell, although he fully admitted the probability of its having 

 also another unknown function, as shown by its development in some 

 anosmatics. It has an intimate connection with the frontal lobe, and in 

 Broca's opinion this last-named lobe owes its supposed importance as a special 

 organ of intelligence to its connection with the olfactory region ; since in most 



htppocampat — 

 fissure 



glomeruli. 



Hippocampus 



a lee us 



cells of 

 precommissural 

 area. 



Fig. 349. — Diagram to show the connections of the olfactory organ with the 

 hippoeainpal region. — Elliot Smith. 



mammals the chief impressions derived from the external world are ob tamed 

 through the medium of the olfactory sense. 2 



Terrier found that " the effects of electrical irritation of the hippo- 

 campal lobule in the monkey and other animals are such as may be 

 most reasonably interpreted as being indicative of subjective olfactory 



1 "Mem. snr le cerveau," Paris, 1888. Broca's distinction of these regions of the Drain 

 (rhinenccjjhalon, Turner) from all the rest of the cortex {pallium) has been followed by all 

 subsequent writers (Schwalbe, " Neurol ogie " ; Zuckerkandl, "Ueber das Riechcentrum," 

 1887; Turner, Journ. Anal, and Physiol, London, vol. xxv. ; Retzius, "Das Men- 

 schenhirn," Stockholm, 1897. The rhinencephalon is phylogenically and ontogenically 

 the oldest, and in many vertebrates remains throughout life the most important part of 

 the cortex. 



2 P. Broca, "Local, cerebrales." "Rech. sur les centres olfactifs," "Memoires," 1888, 

 pp. 424, 429. 



