15° 



C. Judson Herrick 



true, though \v¡th certain qualifications. Its relations seem to be closer 

 with the lateral olfactory nucleus than with either of the other subdivi- 

 sions of the área olfactoria and the fiber connections described indícate 

 that it is a center of correlation between the olfactory systeni and various 

 nonolfactory Systems of the thalamus. These thalamic connections are 

 similar to those of the área somática next to be considered. 



5. The área somática (Johnston, 191 1 a) lies directly behind (spinal- 

 ward) the área olfacto-somatica in the contraeted posterior part of the 



telencephalon médium (fig. 5)- It con- 

 tains a coUection of nerve cells which 

 are directly continuous with those of the 

 dorsal part of the thalamus. This part 

 of the thalamus is known to be a correla- 

 tion center for visual and other extero- 

 ceptive or somatic senses. There are 

 ascending fibers from this thalamic cen- 

 ter to the área somática (fig. 2, tr. th. f.) 

 and descending fibers from the latter to 

 5 the efferent centers of the ventral part of 



Fig. 5.-Diagrammatic transver- ^he thalamus (fig. 2, tr. SOm. /.). These 



se section through the posterior are precursors of the thalamic projection 



end of the telencephalon médium 



of Acipenser at the level of the fibers of higher vertebrates. 



optic chiasma, illustrating the po- -pj^^ ^^^^ somática of the telencephalon 



sition oí the somatic área, iiased ^ 



on Johnston (191 1 a, fig. 48;. of Acipenser is, accordingly, of the same 



anatomical and physiological type as the 



non-olfactory part of the diencephalon, that is, the thalamus proper, with 



which it is immediately confluent. It is in fishes very small, as is also 



the thalamus proper in comparison with the epithalamus and hypothala- 



mus between which it lies. The área olfacto-somatica of Acipenser lies 



directly in front of the área somática and is of the same physiological type 



so far as the thalamic connections are concerned. This área, however, 



has an olfactory component in its physiological pattern. 



The área olfactoria lateralis, área olfacto-somatica, área somática, and 



thalamus form a longitudinal cellular column which is purely olfactory at 



its rostral end and a non-olfactory somatic sensori-motor correlation 



center at its caudal end, with various admixtures of the two systems in 



between. Under the inñuence of ascending fibers from the thalamus 



