100 F. W. STEWART 



boimdaiy definition afforded by the method, rendered the 

 fixer particularly desirable. 



A review of the rather extensive literature on the nervus 

 ternriinalis seems unnecessary, inasmuch as the presentation 

 offered by Larsell ('18) is quite complete. Attention should be 

 called, however, to the fact that in studies on the origin of the 

 ganglion cells of the nervus terminalis, the older literature has 

 been somewhat neglected. I refer to general descriptions deal- 

 ing with the origin of the fila olfactoria rather than to specific 

 papers concerned with the nervus terminalis. Disse ('97) has 

 shown that in the bird, the fibers of the nervus olfactorius are 

 outgrowths of typical cells of the olfactory epithelium — neuro- 

 blasts — and has noted the presence of ganglion cells appearing 

 simultaneously among the growing fila olfactoria. Disse noted 

 the massing of cells of the olfactory fila into an 'olfactory gan- 

 glion' and observed the similarity of cells, situated in the 'gan- 

 glion' and in the olfactory fila to those of the olfactory pit. He 

 regarded them^ neuroblasts which had wandered out from the 

 wall of the olfactory pit. Disse figures both unipolar cells with 

 processes directed centrally, and bipolar cells — one process 

 directed toward the olfactory epithelium, the other passing 

 centrally (his figs. 6, 7, and 8). The observations of Disse con- 

 firmed the earlier findings of Pogojeff ('88) and likewise had 

 bearing on such suppositions as that of v. Lenhossek ('92) to 

 account for the presence of free nerve terminations in the olfac- 

 tory epithelium. The former observed bipolar cells among the 

 olfactory fila of petromyzon. The interpretation of v. Len- 

 hossek may be summed up in a brief quotation: ''Es konnte sich 

 hochstens um Nervenzellen handeln, die in den Verlauf der 

 Olfactoriusbiindel eingeschaltet sind. Hierfiii' sind einstweilen 



2 "Fassen wir den am Riechnerven gewonnenen Befund kurz zusammen, so 

 ist nachzuweisen, dass ein kleiner Teil von Neuroblasten den Epithelbezirk, in 

 dem er enstanden ist, verlasst, und in das anstossende Mesoderm einwandert. 

 Soweit es sich beurteilen lasst, liegen die ausgewanderten Neuroblasten einzeln 

 imd bilden niemals Gruppen; sie zerstreuen sich liber den ganzen Verlauf des 

 Riechnerven, und treten in Verbindung mit dem centralen Ende, sowie mit dem 



Ursprungsbezirke dieses Nerven Die aus diesen Zellen zur Riech- 



grube ziehenden Nervenfasern endigen frei an der Oberflache der Epithels." 



