742 
MR. A. SANDERS ON THE ANATOMY OF THE 
rounded form; it penetrates only a short distance into the posterior end of the 
olfactory lobe so that the ventricle of this is but small. 
Prof. Burt. G. Wilder* gives a different interpretation to these facts. He con¬ 
siders that the ventricles in the olfactory lobes are the true lateral ventricles, that the 
apertures by which they communicate with the ventricles of the cerebrum are the 
foramina of Monro, and that the walls of the cerebrum are what he proposes to call 
the “ prothalami,” connected by the crura thalami with the optic lobes, and 
that the ventricles which they contain are simply the forward continuation of the 
third ventricle. There are many objections to this mode of interpretation; the 
ventricles in the cerebrum and their continuation backward into the third ventricle 
fulfil all the requirements of the case ; but principally the structure of the olfactory 
lobes would forbid their being interpreted as cerebral hemispheres, which would have 
to be the case if their cavities were to be looked upon as lateral ventricles. 
The third ventricle extends interiorly into the ventricles of the hypoaria, which in 
the species under consideration, viz., Scyllium, is broad from side to side, and narrow 
from above downward; posteriorly it ends in two lateral pouches, between which, in 
the midline, is a communication with a cavity in the interior of the hypophysis 
cerebri, which cavity is lined by a continuation of the endothelium lining the 
ventricle of the hypoarium. 
The arrangement in Bhina and Acanthias resembles that of Scyllium, but in the 
former all the cavities are more extensive. On the other hand, in the Bays all the 
ventricles are smaller and more contracted ; the fourth ventricle is a comparatively 
narrow deep fissure, the ventricle of the optic lobe is a small triangular enlargement 
of the aqueduct of Sylvius, and communicates by a narrow passage with the third 
ventricle. The lateral ventricles are non-existent, only a single very small cavity 
extending for rather less than one quarter of its length into the parenchyma of 
the posterior inferior margin of the cerebrum remains as the representative of the 
foramen of Monro (fig. 18 ). 
Microscopic Anatomy of the Brain. 
Lohi Olfactorii. 
The olfactory lobe may be looked upon as consisting of two parts, the lobe proper 
and the peduncle, but this classification is merely superficial, as in structure they pass 
gradually into each other. The lobe itself is more or less pear-shaped, broader at the 
anterior end, where it abuts on to the olfactory organ, and narrower behind, where it 
is attached to the peduncle. 
The olfactory lobe may be described as consisting of three layers placed one in front 
of the other. The internal, which is also the posterior layer, occupies more than half 
of the lobe at the posterior extremity, and consists entirely of a mass of small cells 
embedded in a network of fibrillse and granular neuroglia. In front of these is seen 
* ‘Philadelphia, Acad. Nat. Sci. Proc.,’ 1870. 
