NERVOUS CENTRES. 
(Human Anatomy. Tor Encernatoy.) 671 
Fig. 381. 
= 
The superior and part of the lateral surfaces of the encephalon, exposed by the removal of the calvaria. The 
falx cerebr 
hich i is seen ee longitudinal fissure. 
which present some degree of symmetrical character. 
the hemispheres of the abs ‘a 
the highest level, corresponds to the anterior 
fossa of the cranium. It rests, therefore, upon 
the roofs of the orbits, and its surface is on 
each side slightly concave to adapt it to the 
form of its resting-place. The continuation of 
the anterior median fissure separates its right 
and left portion, and the attachment of the falx 
to the crista galli of the ethmoid makes the 
distinction more complete. Ina distinct sulcus, 
rallel to and immediately on each side of the 
ongitudinal fissure, we find the olfactory pro- 
cess ornerve. This segment forms the inferior 
surface of what anatomists commonly designate 
as the anterior lobes of the brain. It presents 
the convoluted appearance which is conspicuous 
on the proper cerebral surface every where. A 
curved fissure of considerable depth, called the 
The figures on the convolutions indicate those of opposite sides 
They will be referred to further on in the description of 
fissure of Sylvius, is the posterior limit of each 
anterior lobe. 
The fissure of Sylvius corresponds on each 
side to the posterior concave edge of the lesser 
ala of the sphenoid bone, which is received into 
it. It may be traced from within, commencing 
at a triangular flat surface (locus perforatus 
anticus ), which corresponds to the posterior 
extremity of each olfactory process. From this 
situation it proceeds outwards and curves back- 
wards and a little upwards; its convexity is 
therefore directed forwards. Towards the lateral 
surface of the brain it becomes continuous with 
the fissures of neighbouring convolutions. 
The fissure of Sylvius is of considerable 
depth, especially at its internal extremity, and, 
like all the fissures of the brain, large or small, 
