106 LABORATORY OUTLINE OF NEUROLOGY 



septum. See'Herrick ('18), Fig. 52. It is reached by the 

 medial olfactory tract. 



The area olfactoria intermedia lies between the two areas last 

 mentioned and includes the anterior perforated space (in lower 

 mammals the tuberculum olfactorium). It is reached by the 

 intermediate olfactory tract, part of these fibers first decussat- 

 ing in the anterior commissure. 



Tracts of the third order arise from all parts of the olfactory 

 area, and these will be considered under two heads: (1) the 

 reflex tracts, and (2) the cortical tracts. 



125. Reflex olfactory tracts. These pass from the olfactory 

 area to the brain stem centers in the amygdala, diencephalon, 

 and cerebral peduncle. Most of them can be dissected in the 

 brain of the sheep. See Herrick ('18), Fig. 106. 



(1) Tractus olfacto-mamillaris. This is a diffuse collection 

 of fibers from the medial and intermediate olfactory areas 

 passing backward dorsally of the optic chiasma to enter the 

 corpus mamillare. It can be dissected, though with some dif- 

 ficulty on account of the scattered arrangement of its fibers. 



(2) Tractus olfacto-habenularis. Fibers originating with 

 those last described can be seen in a careful dissection to 

 separate from them below the interventricular foramen and 

 then to turn dorsalward immediately behind the foramen. 

 They enter the stria medullaris thalami, a strong superficial 

 fiber tract passing across the rostral border of the thalamus and 

 bordering the tsenia thalami. This tract is sometimes called 

 the tractus tsenise; it terminates in the habenula. 



(3) Tracing olfacto-tegmentalis. These fibers originate with 

 those of the tractus olfacto-mamillaris, but instead of terminat- 

 ing in the mammillary body they pass on to enter the tegmen- 

 tum of the cerebral peduncle. They can be dissected, though 

 they are hard to separate from tractus olfacto-mamillaris. 



(4) The olfactory projection tract of Cajal passes from the 

 lateral olfactory area and amygdala backward into the regions 

 of the mammillary body and cerebral peduncle. We have not 

 been able to dissect these fibers, but they can be demonstrated 

 microscopically. 



(5) Stria terminalis. This tract (also called stria or taenia 

 semicircularis) connects the medial olfactory area in the vicin- 



