CHAPTER V 



FUNCTIONAL ANALYSIS, CENTRAL 

 AND PERIPHERAL 



THE brain of Amblystoma performs three general classes of func- 

 tions, with corresponding local differentiation of structure. We 

 recognize, accordingly, three zones on each side — a dorsal receptive 

 or sensory zone; a ventral emissive or motor zone; and, between 

 these and infiltrating them, an intermediate zone of correlation and 

 integration. 



THE LONGITUDINAL ZONES 



Figures 4 and 5 are sketches of longitudinal sections of the cere- 

 brum of adult Amblystoma tigrinum to illustrate the areas included 

 in the motor and sensory zones as here arbitrarily defined. The zones 

 of the medulla oblongata as seen in transverse section are shown in 

 figure 9. The sensory zone includes those parts of the brain which 

 receive afferent fibers from the periphery, together with more or less 

 closely related tissue of correlation. The motor zone includes those 

 parts from which efferent fibers go out to the periphery, together 

 with related apparatus of motor co-ordination. Both these zones 

 contain some areas which, though not directly connected with the 

 periphery, are nevertheless primarily concerned with specific types 

 of sensory or motor adjustment. What is left over is assigned to the 

 intermediate zone, and whether a particular area will be included 

 here depends on one's estimate of its preponderant physiological 

 character. The body of the cerebellum and the pallial part of the 

 cerebral hemispheres are excluded from the zones as supra-segmental 

 structures. 



The lines drawn in this analysis are frankly arbitrary, chosen pri- 

 marily for convenience of description; but, as will appear, this func- 

 tional analysis contributes to an understanding of the meaning of the 

 structure, and, moreover, it has morphological justification as well. 

 These zones are not autonomous units when viewed either struc- 

 turally or physiologically. Their interconnections are intimate and 

 complicated. The more important of these connections are shown in 



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