THE CEREBRUM 411 



proprius. It is sometimes divided into anterior and posterior 

 parts by a small sulcus called the superior parietal sulcus. 



Lobulus Parietalis Inferior. The anterior and the superior 

 boundaries, and the anterior part of the inferior boundary of 

 the inferior parietal lobule are quite definite, but the posterior 

 boundary and the posterior part of the inferior boundary 

 are arbitrary lines. The superior boundary is the sulcus 

 interparietalis proprius ; the anterior boundary is the inferior 

 post-central sulcus ; the inferior boundary is formed by the 

 posterior part of the posterior ramus of the lateral fissure, and 

 an imaginary line drawn backwards from the point where the 

 posterior ramus of the lateral fissure turns upwards, to a 

 second imaginary line, drawn from the lateral part of the 

 parieto -occipital fissure to the pre-occipital notch on the 

 infero-lateral border. The last-mentioned line, and the lateral 

 part of the parieto-occipital fissure form the posterior boundary 

 of the parietal lobe, and separate it from the occipital lobe 



(Fig- i55)- 



The Sulri of the Inferior Parietal Lobule are the upturned 



ends of the posterior ramus of the lateral fissure, and the 

 superior and middle temporal sulci, which extend from the 

 temporal lobe into the inferior parietal lobule (Fig. 152). 



The Gyri of the Inferior Parietal Lobule are three in number 

 the supra-marginal, the angular, and the post-parietal 



The supra-marginal gyrus surrounds the upturned end of 

 the posterior ramus of the lateral fissure. 



The angular gyrus surrounds the upturned end of the 

 superior temporal sulcus ; and, in a similar manner, the post- 

 parietal gyrus, when it is well marked, surrounds the upturned 

 end of the middle temporal sulcus. It is separated from the 

 arcus parieto-occipitalis by the sulcus par-occipitalis. 



Lobus Temporalis. The temporal lobe appears on the 

 lateral and the inferior surfaces of the hemisphere, and it forms 

 the lower wall of the posterior ramus of the lateral fissure. 



The Sulci on the Lateral Surface of the Temporal Lobe are 

 the superior and the middle temporal sulci. 



Sulcus Temporalis Superior. The superior temporal sulcus 

 lies parallel with the posterior ramus of the lateral fissure 

 (Figs. 152, 155). It intervenes between the superior and 

 the middle temporal gyri ; and it consists of two genetically 

 distinct portions an anterior and a posterior, which some- 

 times remain separate, even in the adult. 



