PEOSENCEPHALON OF MAMMALS. 



133 



The f parietal lobe,' P, includes the frontal fold, ?i, n, the anterior 

 and superior parts of the sylvian, e, and supersylvian, y, folds, 

 with the medial, /, and medilateral, m, folds. 



The ( temporal lobe,' T, in- 119 



eludes the posterior part of 

 the sylvian fold, the postsyl- 

 vian, and subsylvian folds, 

 fig. 115, f,f, and also part of 

 the supersylvian fold, g. 



The l occipital lobe,' o, is a 

 more natural division, includ- 

 ing all the part of the hemi- 

 sphere which lies behind the 

 lambdoidal fissure, is. 



The anterior lobe has three 

 surfaces, one applied to the 

 calvarial part of the frontal 

 bone, another to the orbital 

 plate, a third to the falx. 

 Each of these are impressed 

 by secondary fissures, which 

 I have called ' frontal,' ( or- 

 bital,' and ( falcial,' accord- 

 ingly. The frontal fissures 

 mainly affect a longitudinal 

 direction, but run behind into 

 a transverse one. This is the 

 * frontal,' or ( postfrontal,' fig. 



119, u ; it is more or less 

 extensive and parallel with 

 the coronal fissure, ib. 12. The 



Constant OI tlie lOngltU- superior surface of the right hemisphere of the adult 

 fisSlireS pretty equally human brain, two-thirds nat. size. 



bisects the frontal surface; it is the ( midfrontal ' fissure, fig. 116, 

 14"; the fissure above or internal to it is the ( superfrontal,' u', 

 that beneath or external is the ( subfrontal,' fig. 115, 14 /X/ ; beneath 

 this again and upon the outer and back part of the frontal lobe 

 is a deep and constant longitudinal fissure, usually bifurcate, the 

 ectofrontal, ib. 14 X . 



The fissures on the orbital surface present much analogy to the 

 frontal ones. The posterior one is transverse and usually curved 

 with the convexity forward ; it is the orbital or postorbital, fig. 



120, 16 ; the most constant of the longitudinal fissures which 



