201 



culum has been demonstrated. It is only the most probable inter- 

 pretation to look upon the tuberculum as olfactory" i). 



On many occasions 2) I have called attention to the fact that the 

 size of the tuberculum varies directly with that of the bulbus olfac- 

 torius and that it disappears in the anosmatic Cetacea. For some 

 years I have been in possession of facts which demonstrate its direct 

 connection with the olfactory apparatus; but I have not hitherto con- 

 sidered it necessary to produce this evidence because the olfactory 

 nature of the tuberculum had not been called in question. 



But Professor Edinger has just sent me the proofs of a memoir^) 

 in which he puts forward the suggestion that the tuberculum olfac- 

 torium is the "centre" for those branches of the trigeminal nerve 

 which innervate the snout and subserve the "oral sense". 



His argument may be briefly summarised as follows: — In the 

 year 1904, in conjunction with Wallenberg and Holmes, he discovered 

 a large area behind the olfactory bulb on the base of the forebrain in 

 birds, which was subdivided into a lateral lobe (Nucleus basalis) and 

 a mesial (Lobus parolfactorius). Wallenberg found that a lesion of 

 the brain-stem immediately in front of the insertion of the trigeminal 

 nerve was followed by degeneration in a clearly defined tract of fibres 

 passing forwards to the region of these lobes. Edinger and Ariens- 

 Kappers found that in the brain of the Chameleon the lobus par- 

 olfactorius attained an enormous development, although the olfactory 

 apparatus itself was atrophied. The Chameleon's chief means of ob- 

 taining food is its extraordinary tongue. "Nur hatten wir den Lobus 

 parolfactorius, resp. das Mesostriatum der Vögel deshalb als einen 

 Zentralapparat für die Bewegungen des Schnabels »angesprochen, weil 

 nicht nur Bahnen aus dem Trigeminusendgebiet in seine Nähe, son- 

 dern, was noch nicht erwähnt ist, Züge ebendaher bis in die Mitte der 

 Oblongata degenerativ festgestellt waren (Wallenberg). Auch Reiz- 

 versuche, die Kalischer an Papageien angestellt hatte, ergaben, daß 

 elektrische Ströme, welche das Mesostriatum treffen, Schnabelbe- 

 wegungen hervorrufen" (p. 154). 



The results of these comparisons of avian and reptilian brains 



1) Trabajos del Laboratorio de Investigaciones biologicas de la 

 Universidad Madrid, Tomo 1, 1901 — 1902, p. 85. 



2) See, for instance, "The Cerebrum of Notoryctes typhlops". 

 Transactions of the ßoyal Society of South Australia, 1895, p. 177. 



3) Ueber die dem Oralsinne dienenden Apparate am Gehirne der 

 Säuger. 2. Jahresversammlung der Gesellschaft Deutscher Nervenärzte, 

 1908, p. 151 — 160. 



