Literary Notices. vii 



2. The high prominent mantle-border or rim which surrounds 

 the depression is divided by intervening angles into four sections, 

 viz.: the te?riporal, or lower; \.\\t frontoparietal, or upper ; \hQ frontal, 

 which is formed by an opening out and flattening of the primititive 

 single anterior angle ; and an orbital, or front portion. 



3. Each of these portions of the bounding rim acts as an in- 

 dependent line, ot growth, and consequently, in course of time, four 

 opercula grow over the Sylvian area so as to enclose it. The tempo- 

 ral and frontoparietal opercula appear first ; the frontal and orbital do 

 not develop until a much later period. 



4. The so called three limbs of the fissure of Sylvius are formed 

 by the meeting over the Sylvian area of the contiguous lips of the four 

 opercula ; the posterior horizontal limb intervenes between the fronto- 

 parietal and the temporal opercula ; the anterior ascending limb be- 

 tween the frontal and fronto parietal opercula; the anterior horizontal 

 limb between the frontal and the orbital opercula. 



5. The frontal operculum is therefore the same as the " cap de 

 Broca," and it shows great variations in its length. It may be absent 

 altogether and then the two anterior limbs of the Sylvian fissure are 

 fused into one. When the frontal operculum is reduced in length we 

 have the Y condition of the two anterior Sylvian rami. 



6. The Sylvian fossa once mapped out on the surface of the 

 hemisphere, it extends very rapidly. The growth is not proportionate 

 with that of the hemisphere, it is much more rapid. 



7. During intra-uterine life the anterior end of the insula main- 

 tains a very nearly fixed position with reference to the anterior end of 

 the cerebrum, whilst the posterior end of the cerebrum moves rapidly 

 towards the occipital pole. After birth the posterior end of the insula 

 is fixed, whilst the anterior end, as growth advances, oscillates slight- 

 ly — at first approaching and then retreating from the anterior end of 

 the cerebrum. 



8. An anterior limb of the Sylvian fissures can only be deter- 

 mined by the following tests : (a) it must cut right through the entire 

 thickness of the operculum and reach the furrow surrounding the 

 island of Reil. (b) It must lie in front of the praecentral sulcus. 



9. A single anterior limb of the Sylvian was present in 30 per 

 cent, of the hemispheres exammed ; the two anterior limbs quite dis- 

 tinct and separate were present in 37.5 per cent.; the Y-shaped condi- 

 tion of the two limbs was present in 31.5 per cent. 



10. The two orbital limbs of the Sylvian fissure cannot be re- 

 garded as belonging to the same category of the true anterior limbs. 



