544 HANDBOOK OF PHYSIOLOGY ^ NEUROPHYSIOLOCn' I 



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FIG. 9. Records from the middle region of the rabbit's olfactory bulb showing the differential 

 sensitivity of neighboring mitral units. In this case, acetone gives only large spikes; amyl acetate 

 gives large and small; and pentane gives only small spitces. [From .Adrian (9).] 



ANTERIOR BULB 



POSTERIOR BULB 



AMYL HEPTANE 



ACETATE 



FIG. ID. Integrator records of the spike discharges from the 

 anterior and posterior areas of the olfactory bulb following 

 stimulation by heptane and amyl acetate. The responses indi- 

 cate a differentiation in both space and time. [."Kfter Mozell 

 & Pfaffmann (72).] 



axons arising mainly from the tufted cells and trav- 

 ersing the anterior commissure to reach the opposite 

 olfactory bulb. The existence of a medial olfactory 

 stria conveying fibers from the bulb to the septal 

 area appears unlikely (40- Although the tuberculo- 

 septal tract is often stated to conve\ impulses from 

 the olfactory tubercle to the septum, this tract arises 

 largely in ihc nonolfactorv part of the olfactor\ 

 tubercle (15). 



Extent oj Primary Olfactory Cortex 



NEUROA.N.ATOMiCAL INVESTIGATIONS. Removal of the 

 olfactory bulb in the rabbit (34) and monkey (67) is 

 follovvfed by degeneration of fibers running in the 

 lateral olfactory tract to reach the olfactory tubercle, 

 the frontal prepyriform cortex, the temporal prepyri- 

 form cortex, the cortical and medial amygdaloid 

 nuclei and the bed nucleus of the stria terminalis. 

 The general arrangement of these structures is shown 

 in figure 1 1 . An essentially similar distribution occurs 

 in the marsupial phalanger (i). No degeneration has 

 Ijeen seen in these studies in the hippocampal forma- 

 tion nor in the posterior pyriform cortex (entorhinal 

 area), nor is there evidence of a medial olfactory 

 tract establishing direct cingulate or septal connec- 

 tions. 



Following inoculation of the olfactory mucosa of 

 rhesus monkeys with poliomyelitis virus, Bodian (25) 

 has found degeneration in the olfactory tubercle, the 

 nucleus of the diagonal band, the prepyriform cortex 

 and the periamygdaloid cortex. Some degeneration 

 also occurs in the hypothalamus, the mid-line thalamic 

 nuclei, the habenular nucleus and the globus pallidus. 

 No degeneration was .seen in the hippocampal forma- 

 tion or entorhinal area, nor in the lateral thalamus, 

 putamen or caudate nucleus. 



