ORBITAL CONVOLUTIONS. 



283 



THE CONVOLUTIONS OF THE PARIETAL LOBE. 



The ascending lies behind the fissure of Rolando, and 

 runs upward and backward, an,d is continuous with the 

 superior parietal, which is continued backward to the 

 parieto-occipitaj fissure. The supra-marginal convolution 

 lies behind the ascending parietal. It is frequently con- 

 tinuous with the angular, 

 which bends abruptly 

 downward. The intra- 

 parietal fissure separates 

 the supra-marginal from 

 the angular convolution. 



OCCIPITAL CONVOLUTIONS. 



The occipital convo- 

 lutions are obliquely 

 placed, and separated by 

 secondary fissures, which 

 vary much in extent and 

 depth. 



The temporo-sphe- 

 noidal convolutions are 

 horizontally disposed and 

 separated by deep and 

 well-marked fissures, one 

 of which (that below the 

 first temporo-sphenoidal 

 convolution) is called the 

 parallel fissure. 



The orbital convolutions are three in number. They 

 rest on the orbital plates of the frontal and on the lesser 

 wings of the sphenoid. They are designated the ante- 

 rior, posterior, and inner, the latter lying parallel with 

 the commencement of the marginal convolution. These 



FIG. 122. ORBITAL SURFACE OF THE 

 EEFT FRONTAL, LOBE AND THE ISL- 

 AKD OF RKII, , THE TIP OF THE TEM- 

 PORO-SPHENOIDAL, LOBE HAS BEEN 

 REMOVED. 



17, convolution of the margin of the longitudinal 

 fissure: O, olfactory fissure, with the olfactory lobe re- 

 moved: TR, triradiate fissure: 1" and 1'", convolu- 

 tions of the orbital surface : 1. 1, 1, 1, under surface of 

 the infero-frontal convolution ; 4, under surface of the 

 ascending frontal, and ft, of the ascending parietal con- 

 volutions ; C, central lobe, or island. 



