476 PEOr. G. ELLIOT SMITH ON THE MOEPHOLOGT OF THE 



I may pass over the consideration of the works of the brothers Ramon y Cajal, of Koppen, Schulgiu, 

 Botazzi, Maracino, and Milia, because they contribute nothing fresh to the morphological problem under 

 discussion, and as they have been reviewed by Edinger (Abhandl. d. Seuckeuberg. Gesell. 1896, pp. 318- 



319). 



In 1892 a most important contribution to the discussion of the problem made its appearance, its 

 author l)eing Adolf Meyer (" Ueber das Yorderhirn eiuiger Reptilien," Zeitsch. f. wiss. Zoologie, Bd. Iv. 



p. 63). 



Meyer attempted to institute comparisons between the Reptile and the foetal, rather than the adult, 

 Mammal. He called the paraterminal body the "septum lucidum," but this loose application of a term, 

 which is strictly associated with a special modification of the dorso-caudal extremity of the paraterminal 

 body, and which is found only in the more highly organized j\Iammalia, can hardly be regarded as happy, 

 and at the outset prejudices the chance of an exact comparison. He described a furrow in certain 

 Reptiles, which marks the line of demarcation between the paraterminal body and the cortical area, 

 which I have referred to as hippocampus. This furrow is the fissura limitans hippoccmipi, and Meyer 

 homologized it with the furrow which separates the so-called " Randbogeu" into outer and inner arcs. 

 While this comparison with the somewhat problematical " Randbogen " of the Mammalian foetus is 

 unfortunate, he further compared the cortical portion of the mesial wall of the Reptilian brain with the 

 " outer Randbogen " of the mammal, but he did not commit himself to any more precise homology 

 than this. 



He declined to call the dorsal commissure " corpus callosum," as Osborn, Edinger, and most writers 

 before him liad done. The reason for this is not that the fibres arise from the region which he compared 

 with the " outer Randbogen," but becarise the commissure in question is situated in the lamina terminalis, 

 and not in a secondary fusion of the mesial walls of the hemisphere. This argument is fallacious, as it 

 is based upon a misconception as to the real position of the primordial corpus callosum. 



In 1896 Edinger once more reconsidered the whole question of the morphology of the mesial wall of 

 the liemisphcre in Reptiles ; and, as I have already mentioned, he then corrected the errors which he 

 committed in 1893. He approached the study of this subject again, not only with the much wider 

 knowledge which his own researches has yielded, but with the benefit of the results of the work of 

 Spitzka, Brill, Herrick, and especially Meyer, on the Reptilian brain ; and of Symington, Hill, and 

 myself, upon the lirain of the Proto- and Metatheria. Von Kolliker also, in the same year, added the 

 weight of his authority to the controversy, but apparently merely as the interpreter of the data collected 

 by the writers quoted above. Indeed, the view with which the names of Edinger and Kolliker became 

 associated in 1896 is so plausible and so insidiously deceptive that it is necessary to state it at some 

 length, with the objections to it. In 1894 Kolliker stated that some of the uncrossed fibres of the 

 formx in the Mannnalian brain are derived from the gyrus foruicatus — that is, from a part of the 

 neopallium beyond the limits of the hippocampus *. In reviewing this work shortly afterwards, 

 Edinger t tised the term 7?aw6?!t7»«?;«J9 as a synonym fo;- "gyrus foruicatus"; and elsewhere he subse- 

 quently used the term "gyrus Ibnbicus" in the same sense. I mention this specifically, because both 

 of these terms had been previously used as synonyms for the bidusiuin grisemn, which is not a part of 

 the gyrus Ibrnicatus, but is composed mainly of the vestigial supracallosal portions of the hippocampus 

 {vide Schiifer, ' Quain's Anatomy,' ed. x. vol. iii. pt. 1, 1893, p. 159). In 1896 Edinger spoke of the 

 gyrus limbiciis in nuimmals as the frontal continuation of the " Ammonsrhtdr,'^ " welche nicht mehr 

 eingerollt ist und uber dcm Ventrikel liegt." From the reference to the inroUing, it is clear that the 

 author cannot be using the term " Ammonsrinde" in the literal sense of " gyrus hippocampi" (which is 



* " Ueber don Fornix lougus von Forel,'' Verhandl. d. anatom. Gesellschaft in Strassburg (Anat. Anz. Bd. is. 

 p. 45, Erganzung). 



t " Leistungen auf dem Gebiete der Anatomie des Centralnervensystems," Schmidt's Jahrbiieher, Bd. ccxlvi. 



