NERVUS TERMINALIS IN REPTILE AND MAMMAL 107 



accounted for on the supposition that the cells seen in early 

 stages had developed into neurilemma cells. In Dollken's figures 

 4 and 22 the ner\'us terminalis is distinct from the olfactory 

 nerve and the root c of these figures corresponds to the only root 

 seen by the writer. The fibers of Dollken's root a (fig. 3) appear 

 in my preparations to belong to the olfactory nerve. 



Dollken clearly confirms the work of earlier authors both as 

 to fibers arising from the cells of the vomero-nasal epithelium and 

 as to free nerve endings in this organ. He says: 



Im Ruysch'schen Gang (Jakobson'schen Organ) und zwar nie an der 

 Schleimhautoberflache finden sich spindelforniige Zellen mit einer 

 Fibrillenkontur, die einen Fortsatz in die Nervenstrecke des Nervus 

 terminalis senden (Taf. IV, Fig. 16). Ausserdem laufen glatte Fasern 

 vom Nerven bis zur Oberflache der Schleimhaut, ohne in Verbindung 

 mit einer Zelle des Sinnesorgans zu treten. Diese Fasern sind auch 

 von v. Lenhossek u. A. gesehen und beschrieben worden. Sie kommen 

 in der ganzen Riechschleimhaut vor. Manche Autoren haben die 

 Vermutung geaussert, es konne sich um Trigeminusfasern handeln. Fiir 

 die entspreehenden friihen Fasern des Ruysch'schen Ganges glaube ich 

 diese Annahme ausschliessen zu konnen. Sie stammen von Ganglien- 

 zellen des Terminalnerven. 



From this it is clear that two kinds of fibers are present in 

 the nervus vomero-nasalis of de Vries and nervus terminalis of 

 Dollken, some arising from true olfactory sense cells in the vomero- 

 nasal organ as described by v. Brunn ('92), v. Lenhossek ('92) 

 and Read ('08), and others arising from the cells of the ganghon 

 terminale. 



The vomero-nasal nerve of mammals is not the homologue of 

 the nervus terminalis of fishes. The two nerves exist side by 

 side in mammalian and reptilian embryos. The vomero-nasal 

 nerve arises from cells in the nasal mucosa indistinguishable from 

 typical olfactory sense cells, while the nervus terminalis arises 

 from bipolar ganglion cells situated on the course of the nerve 

 and resembling cerebro-spinal ganglion cells. The vomero-nasal 

 nerve enters the bulbus olfactorius where it has a special part 

 of the formatio olfactoria as its center (the so-called accessory 

 bulb or the formatio vomero-nasalis). The nervus terminalis 

 enters the hemisphere caudal to the bulb in entirely different 

 relations. The nervus terminalis in mammalian embryos is 



