CEREBEAL CO.MMISSUBES IX THE VEKTEBRATA. 477 



rc'uUy in coiitimiity with the gvnis I'oniicatus * ), but as a synonym for tlie more usual name " Ammons- 

 horn," i. e. coruu Ammouis or hippocampus. He further added : " Ich halte es fiir wahrscheinlich, dass 

 in dem Rindeugebicte, welches bei den Reptilien als Aramonsrinde bezeichnete wurde, die Elementc des 

 Gyrus limi)iciis ^</(c/ der Ammonsriude gegcbeii sind " (" I'ntersuchungeu iibcr d. vergl. Anatomic d. 

 Gehirns. 3. Neuc Studien iibcr das \'orderliirn der Reptilien/' in Abhandl. d. Senckcnberg. Gescllsch., 

 1896). Thus, while he was clearlj' using the term " gyrus limbicus" in the sense of the " gyrus fornieatus " 

 he spoke of this structure as the forward continuation of the hippocampus, as if the latter were identical 

 with the pallial area confusedly known as the " hijjpocampal gyrus." The first quotation is so vaguely 

 expressed that one might readily imagine the author to ])e using the term "gyrus linibicus" (or " Raud- 

 windung") in the sense of the inJusiiiin or vestigial hippocampus, as Schiifer does in ' Quaiu's Aiiatomv.' 

 In this ease tlie statement would be quite intelligible; but this interpretation the author never intended, 

 for while in the second cpiotation {siipi^a) he referred to the "Gyrus limbicus iinil der Aramonsrinde," 

 in his ' \'orlesungen,' which were published contemporaneously, he called the imlusium {strire 

 lom/i/inlinales Lancisii) t\w forward continuation of what he somewhat rashly terms the " schon im 

 .\mmonshorne atrophisehen Windung, des Gyrus dentatus." (L. Edinger, ' Vorlcsungen iiber den ]5an 

 der NerviJsen Centralorgane des Menschen und der Tliiere,' 5th ed., Leipsig, 18'JG.) 



It is clear from the foregoing quotations that Edinger, in renouncing his erroneous views of 1893, did 

 not revert to his original belief of 1888. On the contrary, he stated distinctly that the region which he 

 had previously called cornu Ammonis, and of which he now speaks as the " Ammonsrinde," contains 

 the elements not only of the " Ammonsrinde" or hippocampus, but also of the (ji/rus limbicus (or gyrus 

 fornieatus). Some inkling of the meaning of these extraordinary views is obtained from Ediuger's 

 definition of the fornix lum/us as that "welcher aus demjonigen Theile der Randwinduug, welcher 

 nicht zum Ammonshorne sicli einrolltc, aus dem Gyrus limbicus" (Vorlesungen, p. 210). In this 

 statement he was evidently attempting to harmonize the morphology of the cerebral cortex with the 

 supposed grouping of the fibres springing from it. In other words, he argued that the gyrus fornieatus 

 is the anterior continuation of the hippocampus, because tlie fornix is derived posteriorly from the latter 

 and anteriorly from the gyrus (according to the belief of KiiUiker [vide supra] and Edinger). Again, he 

 stated {op. cit. p. 168) that in the higher Mammals, as a consequence of the development of the corpus 

 callosum, the fibres, of the fornix coming from the hippocampus become separated from those which 

 come from the more anteriorly placed part of the " Randwinduug" (meaning the gyrus fornieatus). 



By thus introducing the idea of a " Randwindung " or gyrus marginalis, which includes both gyrus 

 fornieatus and hippocampus, Edinger obviously intends to establish a morphological justification for 

 Kijlliker's belief in the origin of the fornix in part fi-om the gyrus fornieatus. \Vhether any fibres of 

 the fornix ever have any such origin is extremely doubtful {ride "The Fornix Superior," Journal of 

 Anatomy and Physiology, vol. xxxi. p. 90). 



Kolliker in his ' Gewebelehre ' {op. cit. 189(5) ap)n'oved of Ediuger's interpretation, and translated 

 the vague and somewhat cryptic language of the latter into a clear statement, free from all ambiguity. 

 He thus distinctly, though unintentionally, reduced the argument to a reductio ad ubsurdum ! 



Thus Kolliker, whilst speaking of the Re])tilian brain (' Gewebelehre des ^lenschcn,' Bd. ii., zweitcr 

 Hiilfte, 1896, p. 825), writes : — "Edinger hat schon cine Andcutung, ob dieser Fornix der Reptilien 

 nicht dem Fornix hmgus der Siiugcr cntspreche, die ich voU unterstiitzen mochte. Die mediale Waud 

 des Yorderhirnes der Reptilien cntsjiricht ja nicht nur Animonsfalte, sondern audi dem Gyrus forni- 

 eatus der Sanger, aus welchem der Fornix longus entspringt. Ein Fornix inferior kann bei den Reptilien 

 kaum vorhandcu scin, da auch das Ammonshorn, in weleheni derselbe entspringt, nicht gebildet ist." 



This means that Edinger and Kiilliker regarded the cortex of the mesial wall of the llcptiliau 



* I mention this point specitically because elsewhere Ediuger has on several occasions confused the hippocampus 

 and gyrus hippocampi. 



