268 PROFESSOR OWEN ON THE EXTERNAL CHARACTERS 
The size which the brain of the Gorilla acquires in the full-grown male is illustrated 
by the capacity of the cranium, in the paper on that subject (No. IV.) communicated 
to the Zoological Society, November 11, 1851, and published, with illustrations of the 
vertical longitudinal sections, in the fourth volume of the ‘Transactions’ (Pl. XXVIIT.)". 
From these sections an observer, not anatomically acquainted with the disposition of 
the dura mater in relation to the ‘‘ lateral sinuses,” might infer that the cerebrum ex- 
tended backward beyond the cerebellum : it is coextensive therewith in length, but not 
quite in breadth. The Gorilla shows the same degree of development of the ‘‘ posterior 
cornu” and ‘‘ hippocampus minor”’ as has been observed by Van der Kolk and Vrolik in 
the brain of the Chimpanzee. It is the beginning of those structures which are back- 
wardly extended, with the parts of the hemispheres containing them, and fall short, in 
the same degree, of their extended and differently curved homologues, in Man. The 
term ‘‘ rudiment,”’ as applied to the totality of an undeveloped organ, such as the mam- 
mary organs in the male mammal, the hidden tusk in the female Narwhal, &c., cannot 
be applied in the same sense to the commencing extensions of homologous parts in a 
given direction of growth. The stunted tail of the Sloth, for example, is not the 
‘‘ rudiment” or undeveloped representative of the whole tail in the Megatherium ; it 
answers only to two or three of the caudal vertebra at the base of such tail, of which 
huge and complex vertebrz alone, in the Megatherium, the answerable vertebre in the 
Sloth can truly be affirmed to be rudiments. The hinder thumb, in many Orangs 
(seven out of eight observed by Camper (CEuvres, tom. 1. p.54)), is not the homologue of 
the Human hallux, but only of its metatarsal and first phalangeal bones. The begin- 
nings of the posterior cornua and their inflected eminences, in the Gorilla, are shown 
in Pl. XLVIII. fig. 3. 
To supplement the information which the partial decomposition of the exterior 
surface of the Gorilla’s brain left incomplete, a cast was prepared of the cranial cavity 
of an adult male. The brain of the Gorilla, as exemplified by such cast (Pl. XLVIII.), 
is of a narrow-ovate form, with the small end forward: the cerebrum does not extend 
beyond the cerebellum ; viewed with the lower surface of the medulla oblongata hori- 
zontal, it does not extend so far back as the cerebellum does. The difference of size 
between it and a small-sized male Negro’s brain is exemplified in the subjoined admea- 
surements :— 
égale a peine celle d’un enfant qui vient de naitre; et lorsque les dents de lait de celui-ci sont arrivées au 
point ou époque que je citais tout-a-l’heure pour les singes anthropoides, la téte de l’enfant, ou plutédt son 
cerveau, @ acquis un volume double ou triple du cerveau des singes que je lui compare, et il doit accroitre beau- 
coup encore.” (Bulletin de la Société Linnéenne de Normandie, vol. vi. p. 53, 1861.) 
' Reduced woodcuts of the figures were given in the report of the paper which appeared in the ‘ Literary 
Gazette,’ November 15th, 1851, p. 777; that of the adult Gorilla is No. 3. 
* Kuhl takes the correct view of the homologous part, which he shows in the brain of the Aéeles, and calls it 
“ Anfang”? (commencement) “ des hintern, dritten Horns des Seitenventrikels’’ (op. cit. p. 70). 
