252 PROF. HUXLEY ON THE [Jujie 11, 



two, in one of which the cornu was a mere fissure, while in the other 

 it was excessively short, not extending for more than half an inch 

 behind the corpus callosum. 



Thus, not only does the posterior cornu of the lateral ventricle 

 exist in Ateles ; not only has it that backward, outward, and then 

 inward curvature which has been wrongfully asserted to be peculiar 

 to the homologous cavity in the human brain ; but it is, in propor- 

 tion, wider than in the human brain, and it is longer than in many 

 human brains. 



The third point in my argument is the demonstration of the exist- 

 ence of the hippocampus minor. But such strange confusion has 

 been lately introduced into anatomical science, partly by a misappli- 

 cation of well-understood terminology, and partly, to all appearance, 

 by a want of proper acquaintance with the structure aud nomen- 

 clature of the human brain, that I must begin ab initio, by a de- 

 scription of the latter, so far as regards the hippocampi and their 

 related structures. 



The term " Hippocampus minor " was first used by Vicq d'Azyr 

 in the following passage of his famous ' Traite d' Anatomic et de Phy- 

 siologic ' (tome i. 1786), where, in the Explication des Planches du 

 Cerveau, pi. 6. p. 9, I find: — " 26. 46. 4."). SailUe ou relief qui se 

 continue en 26 avec I'origine de la come d'Ammon, et qui en 45 se 

 recourbe en dedans : c'est la partie que Morand a appellee I'ergot*." 



The term " hippocampus minor" has been used in the sense here 

 defined by Vicq d'Azyr by all succeeding anatomists, as the following 

 extract from the celebrated work on Human Anatomy, " Soemmer- 

 ing, vom Bane des menschlichen Korpers," Bd. IV. (Him- und Ner- 

 venlehre, umgearbeitet von G. Valentin) pp. 195, 196, will show : — 

 " Der Sporn, oder die Klaue, oder der Vogelspom, oder die Vogel- 

 klaue, oder der kleine Fuss des Seepferdes, oder der Nagel, oder der 

 Stiefel, oder die Falte, oder der Hahnensporn, oder die hintere, oder 

 kleinere, Wnlst, oder die fingerformige Erhabenheit {calcar s. unguis, 

 s. calcar avis, s. hippocampus minor, s. pes hippocamjn minor, s. 

 eminentia 7ninor, s. digitata, s. unciformis, s. ocrea, s. coUiculus), 

 bildet eine nach ausseu und vorn convex gebogene Erhabenheit der 

 inneren Wand des hinteren Homes des Seitenventrikels." 



"The hippocampus minor forms an elevation, convex outwards 

 and forwards, of the inner wall of the posterior cornu of the lateral 

 ventricle." 



There can, therefore, be no doubt as to what is meant by the term 

 ' hippocampus minor.' 



Another elevation of the wall of the ventricle is known to human 



* " Ce relief est, comme la corne d'Ammon, ou hypocampe, forme d'une lame 

 blanche a sa surface, et, plus profondement, de substance grise : il occupe Tangle 

 interne du prolongement posterieur des ventricles lateraux, comme I'hypocampe 

 celui du prolongement inferieur des memes cavites ; et il ne differe de cette pro- 

 duction qu'en ce qu'il se termine par une pointe mousse, tandisque I'autre s'elargit 

 en s'eloignant de son origiue. On pent done le regarder comme un petit hypo- 

 campe, et le designer sous le nomde hypocampus minor par opposition avec I'hy- 

 pocarapus major, qui est la corne d'Ammon. Cette nomenclature m'a paru plus 

 convenable que celle d'unguis, de colliculus, &c." 



