140 



C. Judson Herrick 



In the discussion of the fiber tracts attention is directed especially to 

 the longitudinal connections of the parts, for the effect of these function- 

 al relationships upon morphological differentiation is the especial theme 

 of this review. The transverse connections, especially the commissures 

 and decussations, are of great importance from many standpoints, but 

 they do not lie within the scope of this paper. 



n.ol. 



tr. som. p 



Fig. 2.— Dingrammatic median section of the forebrain of Acipenser rubicun- 

 dus. The outline is based on figure 2 of Johnston (1911 a). The courses of a few 

 of the fiber tracts to which reference is made in the text are diagrammatically in- 

 dicated from Johnston's descriptions. The área somática (a. som.) and área olfac- 

 to-somatica (a. ol. s.) are indicated as projected upon the medial surface. 



The greater part of the telencephalon médium is reached by secon- 

 dary fibers from the bulbus olfactcrius, that is, it comprises the área 

 olfactoria. Though the olfactory tracts which end in the various parts 

 of this área are, so far as known, of the same physiological type, the área 

 itself is divided into severa! regions or nuclei, each with characteristic 

 internal structure. Since this differentiation within the área olfactoria 

 cannot be accounted for by physiological differences in the olfactory 

 tracts entering from in front, we naturally are led to inquire into the rela- 

 tions of this telencephalic olfactory área at its lower or diencephalic 

 border. 



