104 LABORATORY OUTLINE OF NEUROLOGY 



ependyma of the third ventricle, beginning in the region of the 

 mammillary body. 



(8) Tr actus mamillo-tegmentalis. — By very slight dissection, 

 beginning in the median plane, this tract can be exposed. It 

 runs from the mammillary body dorsalward and spinalward 

 through the tegmental region under the aqueduct of Sylvius. 



(9) Tractus mamillo-peduncularis. This tract arises with the 

 last and runs somewhat farther ventrally in the cerebral pe- 

 duncle. 



(10) Tradus habenulo-peduncularis (fasciculus retroflexus, or 

 Meynert's bundle). This tract also can readily be dissected. 

 It runs from the habenula into the ventral part of the cerebral 

 peduncle immediately behind the mammillary body, crossing the 

 tractus mamillo-tegmentalis at a somewhat deeper level (more 

 laterally) . 



The three tracts last mentioned carry olfactory nervous 

 impulses into the motor centers of the cerebral peduncle. After 

 synapses here the pathways are continued to the lower motor 

 centers. 



126. Cortical olfactory tracts. — All parts of the olfactory 

 area discharge tracts of the third order into the cerebral cortex 

 (hippocampus and gyrus hippocampi). 



(1) Tractus olfado-corticalis medialis. — These fibers ascend 

 from the medial and intermediate olfactory areas close to the 

 median plane between the corpus callosum and the anterior 

 commissure to enter the body of the fornix and fimbria. They 

 are drawn, but not named, in the region marked S in Fig. 106 of 

 Herri ck ('15). They pass through the fimbria to terminate in 

 the hippocampus (see Section 127). 



(2) Stria longitudinalis medialis ("nerve" of Lancisius). A 

 few fibers belonging to the same system as the last pass dorsally 

 instead of ventrally of the corpus callosum. By exposing the 

 dorsal surface of the callosum they can be seen curving around 

 the genu, passing backward along its dorsal surface close to the 

 median plane, then curving ventrally around the splenium to 

 enter the underlying hippocampus (see Burkholder ('12), 

 Plates XI and XII). These fibers are accompanied by the 

 thin gray "indusium verum," which is a vestige of an extension 

 of the hippocampus above the callosum which is found in the 



