206 



the other parts of the central olfactory apparatus — with the pyri- 

 form lobe on its outer side and the hippocampal formation on the 

 mesial side^). It is linked to the latter, not only by direct connections, 

 but also by a nerve tract, which forms part of the cephalic segment 

 of the cingulum, which has been described by Beevor, Zuckerkandl 

 and especially Redlich-). 



In the face of all this varied evidence I do not think it possible 

 to maintain that the tuberculum olfactorium is not connected with the 

 smell-apparatus. Nor, on the other hand, is there any definite proof 

 that it is really a centre for the "oral sense". It is interesting to 

 recall, however, that in many mammals, to the cerebral cortex of which 

 I have applied electrical stimulation, movements of the tongue, jaws 

 and lips have been obtained from excitation of the spot corresponding 

 to that marked ^ in Figure 1. This centre is in the neopallium (i. e. 

 to the outer side of the pyriform lobe) and not in the tuberculum 

 olfactorium (i. e. to the inner side of the same structure). Perhaps 

 the tract of trigeminal fibres which Edinger regarded as being des- 

 tined to end in the tuberculum olfactorium really terminates in the 

 neopallial centre x. 



Conclusion. 



The tuberculum olfactorium is certainly a part of the smell-centre 

 and its function is probably almost exclusively olfactory. 



It is linked to the olfactory bulb by a direct tract, which arises 

 in the forniatio bulbaris. 



Addendum. Since this note has been printed Dr. Aeiens-Kappers 

 has kindly called my attention to the fact that he discussed and rejected 

 the hypothesis of the tactile function of the tuberculum olfactorium (Anat. 

 Anz., Bd. 33, Oct. 17, 1908, p. 333), and Professor Edinger has written 

 to say that Ornithorhynchus was included in his memoir by mistake. 

 It is, however, impossible to ignore the decisive evidence supplied by 

 the brain of Ornithorhynchus, because it has the most highly-developed 

 "oral sense" in the whole series of mammals. It is a common mistake 

 to suppose that Ornithorhynchus has a horny snout; but, as Wilson 

 and Martin have shown (op. cit. supra), the skin covering the bill is 

 of exceptional softness and of extreme sensitiveness. 



1) See for example Livini, II Proencefalo di un Marsupiale, Arch, 

 di Anatomia e di Embriologia, Vol. 6, Pasc, 4, Firenze 1907, tav. 25 

 to 26 ; and Ariens-Kappers, Die Phylogenese des Rhinencephalons, etc., 

 Folia Neuro-biologica, Bd. 1, No. 2, Januar 1908. 



2) Zur vergleichenden Anatomie der Assoziationssysteme des Gehirns 

 der Säugetiere. Arb. a. d. Neurol. Institut an d. Wiener Univ., 1903. 



