THE NERVOUS SYSTEM. 



291 



The principal fissures of the brain are five, as follows : 



1. The great longitudinal fissure, separating the two hemispheres 

 from one another. 



2. The great transverse fissure of Bichat, between the cerebellum 

 and the cerebrum, admitting the pia mater to form the velum inter- 

 positum. 



3. The fissure of Sylvius, beginning at the anterior perforated 

 space and ascending obliquely. 



4. The fissure of Rolando, descends from near the middle of the 

 great longitudinal fissure to join the fissure of Sylvius. 



FIG. 133. 



Left side of human cerebrum. S. fr. s., superior frontal sulcus; 

 S. praec., precentral sulcus; S. R., central sulcus of Rolando; S. poste., 

 Post-central sulcus; S. interp., interparietal sulcus; S. p. o., parieto- 

 occipital fissure; Ram. post. S., posterior ramus of fissure of Sylvius; 

 S. temp, m., middle temporal sulcus; S. temp, s., superior temporal 

 sulcus; F. S., fissure of Sylvius; R. ant. asc. S., ascending anterior 

 ramus of fissure of Sylvius; R. a. h. S., horizontal anterior ramus of 

 fissure of Sylvius; S. fr. inf., inferior frontal sulcus. (After Van 

 Gchuchten.) (Wtiiteliead.) 



5. The paricto-occipital fissure, on the postero-lateral aspect of the 

 cerebrum. 



6. The callaso-marginal fissure. 



7. The collateral fissure. 



8. The limiting sulcus of Reil. 



