NERVOUS CENTRES. (HUMAN ANATOMY. THE ENCEPHALON.) 



CT1 



Fig. 381. 



fhe superior and part of the lateral surfaces of the encephalon, exposed by the removal of the calvaria. The 

 falx cerebri is seen in the longitudinal Jfaswre. The figures on the convolutions indicate those of opposite sides 

 which present some degree of symmetrical character. They will be referred to fvrther on in the description of 

 the hemispfteres of the brain. 



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. In a distinct sulcus, 

 parallel to and immediately on each side of the 

 longitudinal fissure, we find the olfactory pro- 

 cess or nerve. 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 



fissure of Sylvius, is the posterior limit of each 

 anterior lobe. 



The fasure 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, 



