be regretted that so inadequate a figure should have been taken as a typical representation of the Chimpanzee's brain.
3. The Hippocampus minor.—But even supposing that the posterior cornu of the lateral ventricle and its appendage, the hippocampus minor, were absent in the apes, and "peculiar to the genus Homo," what classificatory value would the distinction possess? This, of course, depends upon the constancy of the supposed distinctive character; but it so happens that, as every anatomist knows, the posterior cornu and the hippocampus minor, are precisely those structures which are most variable in the human brain. This is by no means a novel discovery. The work of the brothers Wenzel[1] has now been published nearly half a century, and it contains (pp. 144–146) the following account of the special researches of these observers on the posterior cornu and the hippocampus, which they call simply "Tuber":—
"Tuber in cornu posteriore ventriculorum lateralium:—Non semper plerumque tamen adest, et quidem utroque in latere sive in utroque cornu. Inter quinquaginta et unum, eo specialiter fine a nobis examinata cerebra diversæ omnino ætatis atque utriusque sexus, tria tantum reperiebamus in quibus tuber illud in utroque latere et duo in quibus uno in latere desiderabatur. Quam constans autem, in universum tuberis istius præsentia, tam varans est magnitudo illius, non in diversis tantum subjectis, sed etiam in uno eodemque absque omni prorsus et ætatis et sexus discrimine. Quandoque admodum longum, interdum latum nonnunquam valde augustum est. Magnitudo illius in universum spectata, sequitur magnitudinem posterioris cornu ventriculorum lateralium: hæc quam maxime diversa est, quin et in uno eodemque cerebro et utroque latere. Quandoque enim cornu istud fere usque ad posteriorem cerebri marginem pertingit, sæpe terminus prope initium est, Sæpe contingit ut in minore cornu magis, in majore minus sit tuber, id quoque eodem nonnunquam in cerebro evidentissime animadvertitur. Rarius in hoc tubere est quod sictit hippocampus ad finem suum crenas sive sulcos habeat quod superficies ejus duo in tubera superius atque inferius, divisa sit; plerumque autem in medio latissimum est et crassissimum. in terminis angustius: sed et hoc quoque varium est.
"Situs illius atque interior structura semper sunt eadem. Semper juxta interius latus cornu videtur, ideoque superficiei cerebri prope adjacet, idque cum interiore ejusdem structura cohæret, quae, ut sectio in transversum ducta clare demonstrat, eadem omnino est ac in gyris cerebri. Constat videlicet ex interiore in laterales ventriculos continuato, sive prolongato pariete cujus gyri in superficie cerebri siti, qui inflectitur, ac deinde interiori de parte exteriorem versus ad superficiem cerebri rediens in alium gyrum transit. Paries ist intra cornu medullosa, quœ cornu ipsum vestit, lamina obducitur; paries ipse autem ex cinerea, in ambitu cerebri sita, ubique conspicua substantia constat, quæ hoc loco neque latior est, neque alium colorem exhibet ac in quovis alio cerebri gyro.
"Inter utrumque tuberis parietem spatium invenitur, quod vasculosa cerebri æque explet ac sulcum inter duos alios gyras in superficie cerebri sitas.
"Si in superficie cerebri eo, qui eminentiæ isti opponitur loco membrana cerebri media et interior detrahitur, tuber illud evanescit, ut quamprimum cerebri superficies extenditur, in planum mutatur.
"Discrimen ergo, hoc tuber inter et processum cerebri lateralem in eo consistit, quod illud verum absolutum, gyris in exteriors cerebri superficie sitis omino simile, quoad interiorem vero structuram plane æquale, in interiore cerebro sive in aliqua ventriculorum ejusdam parte existens gyrus sit; quod e contrario hippocampus, si cum gyris in superficie cerebri existentibus comparatur, tantummodo gyri alicujus pars, non autem absolutus atque integer gyrus sit, cujus initium in interiore cerebro, aut in aliqua ventriculorum parte existit."
- ↑ Jos. et Car. Wenzel, "De penitiori structura Cerebri Hominis et Brutorum. Tubingæ, mdcccxii.
