48 LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



divides it into two lobules. The anterior lobule is divided by 

 several perpendicular fissures into 3-4 gyri breves insulae. The 

 posterior lobule is, apparently, one single longer convolution, 

 the gyrus longus. It borders directly on the temporal lobe. In 

 the operculum there begins an important fissure which ascends 

 to the margin of the hemisphere, but is separated from the latter, 

 as well as from the fissure of Sylvius, by brain-substance. This 

 is the sulcus centralis, or central fissure. Observe it in Fig. 28 ; 

 it divides the frontal from the parietal lobe. All that lies below 

 'the fissure of Sylvius is called the temporal lobe. In front of 

 the central fissure lies the anterior central convolution ; behind 

 it, the posterior central convolution.* 



The region in front of the anterior central convolution, the 

 frontal lobe, is divided by two fissures, the superior and inferior 

 frontal fissures, into three convolutions, superior, middle, and 

 inferior frontal convolutions. These are not always sharply 

 defined along the whole length of the frontal lobe, inasmuch as 

 the frontal fissures are often interrupted in their course by plis 

 de passage. You will easily discover these three divisions of the 

 frontal lobe lying next to each other in all brains, and will 

 observe that the lower frontal convolution (also called third 

 frontal convolution) takes part in forming the operculum. Very 

 often there is found at the posterior end of the inferior frontal 

 fissure another fissure at right angles to it, which bounds the 

 anterior central convolution in front and is called the pra3-central 

 fissure. 



[The lower frontal convolution is broader in Europeans than in other races. 

 In the brain of Gambetta, who was a great orator, it was twice as broad as usual.] 



The temporal lobe is traversed by several fissures, which run 

 parallel to the fissure, of Sylvius and divide the lobe more or 

 less sharply into an upper (or first), a middle (or second), and a 

 lower (or third) temporal convolution. Generally only the two 

 first of these are clearly distinguishable throughout their whole 

 length. 



* Circonvolution frontale ascendente, i , 



5 of the French writers. 

 Circonvolution parietale ascendeute, 



