36 
MR, W. BEVAN LEWIS ON THE COMPARATIVE 
The brain of the Pig presents us with four primary divisions or lobes : 1, the great 
limbic lobe ; 2, the parietal lobe ; 3, the frontal lobe ; 4, the olfactory lobe. 
1. The great limbic lobe. —This lobe, seen chiefly on the internal aspect of the hemi¬ 
sphere, consists of a superior arc (convolution of the corpus callosum), fig. 1 (1, 1), 
commencing in front of the corpus callosum where the internal root of the olfactory 
unites with it, bends round the anterior extremity or genu of this great commissure, 
and borders its upper aspect as far as its posterior extremity, where it becomes con¬ 
tinuous with the inferior arc of the same lobe, or the gyrus hippocampi, fig. 1 (2, 2), 
and from which it is marked off by a well-developed retro-limbic annectant (3). The 
anterior half of the upper arc becomes superficial and exposed upon the surface of the 
hemisphere, forming here the border of the great longitudinal fissure (4). The limbic 
fissure, separating this important lobe from the remainder of the hemisphere, may be 
traced in front as a somewhat obscure sub-frontal sulcus (5), and further back as a 
Fig. I. 
deeply-marked sub-parietal sulcus (6), interrupted posteriorly by the retro-limbic annec¬ 
tant (3). Beyond the latter annectant, it can be traced between the parietal lobe and 
the inferior arc of the limbic lobe, i.e., the gyrus hippocampi (8). The anterior ex¬ 
tremity of the sub-parietal sulcus turns upwards towards the surface of the hemisphere, 
and is continued obliquely forwards and outwards as a well-marked crucial sulcus, 
separating the superficial portion of the limbic lobe from the parietal lobe (7). The 
great comparative depth of the anterior portion of the superior arc, when contrasted 
with its posterior half, is well marked in this animal—a feature identified by Broca as 
of constant occurrence in “ Osmatic” Mammals, or those in whom the olfactory appa¬ 
ratus is highly developed. 
2. The 'parietal lobe. —Turning our attention to the external aspect of the hemi¬ 
spheres (extra-limbic mass of Broca), we find by far the greater portion enters into 
the constitution of the great parietal lobe. In this extra-limbic portion we recognise 
readily three primary fissures—the crucial, interparietal, and Sylvian. Still further 
forwards, at the extreme anterior pole of the hemisphere, is a shallow vertical fissure— 
