173 



As was to be expected, in the adults of the mammals the nerve 

 was not first found in man. The dog and the cat (Mc. Cottkr. 

 1913.) and the rabbit (Hubkr & Guild. 1913.) were the first, but it 

 is remaikable that in the embryonic stages of tiie mammals tlie human 

 embryo was the first in which, although incompletely, the nerve was 

 discovered. This was done by our countryman Ernst dk Vriks, 

 who also observed it in the embryos of the gninea-|)ig. He described 

 his research (|)ublished in the Proceedings of the Royal Academy 

 of Sciences of April the 22'"^ 1905), which also drew much attention 

 abroad, in an article of four pages, which proves that it is not ne- 

 cessary or even desirable to be loquacious when one has found 

 something of importance. 



Dk Vries found ganglionic cells spread in the course of the nerve 

 which supplies the organon vomeronasale, (the organ of .Iacohson, or 

 better the organ of Ruysch) ^) near the base of the nasal septum. 

 He moreover found that the so-called olfactory ganglion, by him 

 called tlie ganglion vomeronasale, does not belong to the tila olfac- 

 toria, which are taken collectively as the true olfactory nerve. 

 In his opinion it belongs to the N. Vomeronasalis, which supplies 

 Ruysch 's organ, lined by a layer divided off from tlie nasal 

 mucous membrane. As the vomeronasal nerve also enters the central 

 nervous system at a different place — the area vomeronasalis — than 

 do the fila olfactoria, dk Vries drew the conclusion that the N. Vo- 

 meronasalis is not, as was the general opinion, a component part 

 of the olfactory nerve, but an independent nerve, homologous to 

 the N. Terminalis in the fish. 



A serious difficulty to this explanation however is that, according 

 to the illustrations of dk Vriks, the N. Vomeronasalis issues from the 

 olfactory bulb, while the N. Terminalis of the Dipnoi and the Se- 

 lachii issues out of the true hemisphere and not out of the bull). ") 



This difficulty seems to have escaped dk Vries's notice. On the 

 first page of his publication he rightly distinguishes between the 

 olfactory lobe and the hemisphere, which are separated from each 

 other laterally by the fissura rhinica, and mesially by the fissura 

 prima. On pages 3 and 4 he states that the ai-ea vomeronasalis, 

 where the nerve of this name enters the brain, belongs to the he- 

 misphere. According to his own communication and illustration, 

 however, this area lies at the sulcus circularis bulbi, hence not on 



') Concerning Ruysch's organ see postscript at the end of this paper. 

 2) Entering and issuing out of a nerve are used in this address, indiscriminate 

 of the direction in which the impulse moves. 



