188 
ME. W. H. ELOWEE ON THE POSTEEIOE LOBES 
ture of that organ ; and I must premise that in all the ensuing descriptions the nomen- 
clature used is the one proposed by Mr. Huxley*, founded on that of M. Gratiolet, 
to whom the merit of reducing to an intelligible and harmonious system the apparently 
confused and intricate surface-markings of the brain of the Primates is chiefly duef. 
Plate II. flg. 1 is a sketch of the internal sm’face of the right hemisphere of the bram 
of an adult European. It has been carefully drawn from a specimen which had been 
prepared for the purpose, by injecting the carotid arteries with strong spirit, and harden- 
ing within the cranium, so that the general form and relative situation of the different 
parts have been accurately preserved. Five principal sulci are seen upon this face of 
the cerebral hemisphere. 1. The calloso-margiiial {i, i), running lengthwise, parallel to, 
and between, the upper border of the corpus callosum and the superior margin of the 
hemisphere. 2. A nearly vertical fissure (^’, k) placed about midway between the 
posterior end of the corpus callosum and the apex of the hemisphere. As it forms the 
line of demarcation between the parietal and occipital lobes, it has received the name of 
occijyito-parietal (“ scissure perpendiculaire interne ” of Gratiolet). 3. A deep and 
distinctly marked sulcus (I, 1) commencing just below the posterior extremity of the 
corpus callosum, and running backwards and slightly upwards almost to the apex of the 
hemisphere, where it divides into an ascending and descending branch. This is the cal’ 
carine sulcus, so named from its relation to the part called, when seen from the interior 
of the ventricle, “ calcar avis,” or “ hippocampus minor ” (“ anfractuosite de la cavite 
digitale,” Cruveilhier ; posterior portion of the “ scissure des hippocampes,” Gratiolet), 
4. The dentate- sulcus, in which the small gyrus called “ corpus dentatum ” (corps go- 
dronne) is situated. This is the anterior portion of the “ scissure des hippocampes ” of 
Gratiolet, and holds the same relation to the hippocampus major as the calcarine 
fissure does to the hippocampus minor. 5. A fissure (w, n) running more or less parallel 
to the last, but at a lower level, named from its connexion with the eminentia coUate- 
ralis, the collateral sulcus. The relations of the last three sulci have been pointed out 
in detail by Mr. Huxley in the paper referred to. 
The gyri on the inner surface have their boundaries defined by the above-named sulci, 
and are of a very simple character. They will be better understood by a reference to 
the figure, than by a verbal description. 17 is the marginal gyrus; 18 the callosal; 
18' the quadrate lobule; 19 the uncinate gyrus; 20 the dentate; and 25 the internal 
occipital lobule. 
In the hemisphere of the hardened brain (Plate H. fig. 1) the space between the poste- 
rior edge of the corpus callosum and the extremity of the lobe was divided into four 
equal parts, and the sections indicated by the lines A, B, and C were made at the points 
thus determined. For accuracy of comparison, the same rule has been observed in all 
the sections of the Simian brains which follow. The figures A, B, and C represent the 
surface of such sections, and exhibit the distance to which the different sulci penetrate 
* On tlie Brain of Ateles pmiscus, Proc. Zool. Soc, June 11, 1861. 
t Memoire sur les Plis Cerebraus de THomme et des Primates. Paris, 1854. 
