TKEFACE. xix 



Articles VII.-IX. " Des os du pied,"" the frame of tlie hind 

 feet of Man, Ape, Lion, Seal, Elephant, &c., is shown to consist 

 of homologous bones. Nevertheless the great zootomist, in his 

 labour aud character as zoologist, does not hesitate to define and 

 differentiate the ' foot,' the ' hand,' the ' paw,' the ' fin,' and the 

 ' hoof,' respectively : nor does he deem the demonstration of the 

 unity underlying the diversity to make the ' man ' an ' ele])hant ' 

 or a ' seal,' any more than it makes him a ' dog ' or an ' ape ' ! 



The ' corpus callosum ' is defined as ' a horizontal mass of trans- 

 verse fibres covering the lateral ventricles, and exposed by divari- 

 cating the cerebral hemispheres.' If a group of manmials want 

 such commissural fibres, and another group possess them, the 

 classifier will avail himself of a well-defined term expressing such 

 difference, without prejudice to his recejition of any homological 

 determination of the parts, or their rudiments,^ in anatomical 

 works of the applier of the term. 



Only by ignoring such indication of the ' rudlmental com- 

 mencement of the corpus callosum,' may a semblance of superior 

 knowledge be assumed by him who asserts, as an antagonistic 

 proposition to an affirmation of its absence as a zoological cha- 

 racter, that the Marsupialia, e.g., do possess the ' great com- 

 missure,' or ' corpus callosum.'^ 



So likewise with other well-defined parts of the human brahi, 

 the homologues of which may not be traceable to the same extent 

 down the mammalian series. Kuhl, e.g., in Ateles Bdzehuth,^ 

 TiEDEMANN in the Macafjue'"^ and Orang," Van der Kolk and 

 VeOlik in the Chimpanzee,' and myself in the Gorilla,' had 



' Lemons d'Auat. Comparee, vol. i. 1799. 



- As given in the "Philosophical Transactions' for 1837, p. 41. 



= Proceedings of the Eoyal Society, No. 72, aud March 23, 1865. 



^ Beitrage zur Zoologie und vergleichenden Auatomie, 4to. 1820, zweite Ahtheihuig, 



p. 70, Taf Tii. 



5 Icones cerebri Simiarum, fol. 1821, p. 1-1, fig. iii. 2. 



= TreTiranns, Zeitschrift fiir Physiologic, Bd. ii. ,S. 25, Taf iy. 



' Nieuwe VerhandUngen der erste Klasse ran liet Koningl. Nederlandsche lustituut. 

 Amsterdam, 1849. 



» Fnllerian Lectures ou Physiology, Eoyal Institution (jidaroh 18, 1861); reported, 

 with copies of diagrams, in ' Athenpeum,' March 23rd, 1861, p. 395. 



