TRANSPLANTATION OF HEMISPHERES 163 



normal structure as worked out by Herrick in 1910. Briefly 

 stated, the organization of the telencephalon is this. From the 

 olfactory bulb, running caudal to the dorsal body of the anterior 

 olfactory nucleus and to the posterior pole of the hemisphere is 

 the tractus olfactorius dorsolateralis (fig. 1). A ventral division 

 of this tract, the tractus olfactorius ventrolateralis, runs caudad 

 intermingled with the lateral forebrain tract to the so-called 

 corpus striatum opposite the anterior commissure. Some of 

 the fibers of this tract in all probability enter the anterior olfac- 

 tory nucleus. The lateral forebrain tract, above mentioned, 

 consisting of ascending and descending fibers, runs between the 

 olfactory bulb and the anterior olfactory nucleus and thalamus 

 via the anterior commissure (fig. 2) . On the median side of the 

 hemisphere the tractus-olfactorius dorsomedialis runs from the 

 olfactory bulb caudad to the dorsomedian part of the hemisphere, 

 the area designated by Herrick as the primordium hippocampi 

 (fig. 3). Ventromedially the tractus olfactorius ventromedialis, 

 consisting of ascending and descending fibers, runs from the 

 olfactory bulb to the hjrpothalamus. The paUial portion of the 

 hemisphere, owing to its relative isolation from the rest of the 

 brain stem by the diencephalic flexure, is connected with the 

 brain stem by two relatively small groups of fibers. The first 

 of these, the columna fornicis, runs from the anterior boundary 

 of the primordium hippocampi first ventrad then caudad to the 

 hypothalamus. The second of these is the stria-medullaris, 

 running from the dorsomedian region of the primordium hippo- 

 campi through the commissura pallii anteriora to the pars ven- 

 tralis thalami. 



Two nuclei are apparent in the hemisphere, one laterally just 

 posterior to the anterior olfactory bulb, the anterior olfactory 

 nucleus (nucleus olfactorius anterior) and a second medially, 

 the nucleus medianus septi, situated in the ventro-anterior part 

 of septum ependymale (fig. 2). 



As would be expected, the isolation by transplantation of the 

 cerebral hemisphere precludes the development of nerve fibers 

 which reach the hemisphere from lower parts of the brain stem. 

 That is to say, the ascending fibers of the median and lateral 



