174 



the hemisphere, but on tlie olfactory lobe. In young embryos the 

 ti'act is thicker than the bulb, later on this relation is reversed. 



It was therefore very desirable that more light were thrown on 

 the question whether the vomeronasal nerve should be considered 

 as the homologue of the N. Terminalis of the fishes. 



This happened in 19J3 in America, more especially through two 

 publications viz. of Johnston in the Journ. of Comp. Neur. Vol. 23. 

 and of HuBKH & Guild in the Anatomical Record Vol. 7. ') 



Johnston examined embryos of the pig, the sheej), and of man. 

 Besides mammals he also examined embryos of tortoises and a larva 

 of Amblystoma. 



The elucidation which Johnston brought, consists herein that (as 

 he found) the ganglion and the ganglionic cells do not belong to 

 the N. Vomeronasalis, but to another nerve, which does not enter 

 the brain in the olfactoi-y bulb, but in the true hemisphere, near or 

 in the lamina terminalis, as is the case in the Selachii. 



What DE Vries had considered as one nerve, was in reality two 

 nerves which for the greater part cover each other; one is the N. 

 Terminalis, the other is the true N. Vomeronasalis. 



The vomeronasal nerve has no ganglionic cells and ai-ises out of 

 the cells of a part of the nasal mucous membrane which had been 

 split off (Organon Vomeronasale). In structure and development 

 it is exactly similar to the bundles of the olfactory nerve, it also 

 enters the brain in the olfactory bulb, just as the tila olfactoria, 

 which collectively form the olfactory nerve. It is true that it enters 

 the bulb at a special place, on its mesial plane rising high up 

 caudally, but then it is a specialised bundle of the olfactory nerve. 

 The peripheral ganglionic cells and the true ganglion belong to the 

 N. Terminalis. 



DK Vries' mistake is easily comprehensible; he used no special 

 methods to make the nerves visible, could not expose his material 

 of human embryos to this risk and was thus compelled to considei 

 the proximal end of the N. Vomeronasalis (split into four bundles 

 according to him) as a root of the Ganglion Terminale, by him 

 incorrectly called the Ganglion Vomeronasale, which is as it were 

 pasted up against it, while the true roots of this ganglion escape 

 observation in cross section through their fineness. That it is possible 

 to make mistakes even when using nerve-staining methods is proved 

 by the work of Dollkkn (1909). He examined embryos of mice, 

 rabbits, guinea-pigs and man. Following in the footsteps of de Vries 



Further literature is found mentioned in these publications. 



