50 



LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



latter you will have to be at some pains to distinguish. You 

 will find it in the space which is bounded above by the inter- 

 parietal fissure and below by the superior temporal fissure, its 

 posterior portion, indeed, surrounding the end of the latter. 



Do not always expect, gentlemen, to find the interparietal 

 fissure running its whole course without a break. Often enough 

 it is broken into two or more parts by 2^'^ d & passage, which 

 are usually found in its posterior third. Its posterior portion 

 extends into the occipital lobe. 



This occipital lobe is not in all brains so uniformly divided 



by its sulci that we can always 

 find the three convolutions 

 described by writers, viz., first 

 (upper), second (middle), and 

 third (lower) occipital convolu- 

 tions, easily and without arti- 

 ficial refinement. 



It is often separated from 

 the parietal lobe by an addi- 

 tional occipital fissure (not 

 shown in the figure), which 

 passes up perpendicularly be- 

 hind the gyrus angnlaris. 

 The line of division from the 

 temporal lobe is a horizontal 



fissure, appearing like a continuation of the inferior temporal 

 fissure, and called the inferior occipital sulcus. The angle be- 

 tween these occasionally continuous fissures bounds the temporal 

 lobe. At the upper and anterior part it is continuous with the 

 parietal lobe. This connection is divided into the bridging con- 

 volutions by the interparietal fissure, which passes through it 

 longitudinally. 



After noting all these convolutions and fissures, divide the 

 brain into halves by cutting down through the great fissure and 

 study the median surface. 



Slellc wo Vardcrhtm 

 mi. Iwixhcnliim 



FIG. 30. 



Inner aspect of the embryonic hemi- 

 sphere, shown in Fig. 7. Shows the inner 

 1 >wer border of the hemisphere, which be- 

 comes thickened into the white medullary 

 line of the fornix. The latter, however, only 

 becomes medullary after birth. 



St?He uo Yorderkirn und Zwi$chenih#rn zu.ifim- 

 mfn.itos.ten, Point where the fore-brain and mid-brain 



meet. 



