886 



THE NERVOUS SYSTEM 



bones appears very uneven, and when placed in water presents a flocculent appearance. 

 This is due to the many fine bundles of connective tissue and the blood-vessels 

 which pass between the dura and the cranial bones and which are partially pulled out 

 of their openings in the latter in the process of separation. The abundance of these 

 connections, and, therefore, the degree of adhesion to the bones, varies in different 

 localities. The separation is much less- difficult from the inner table of the bones of 

 the vault of the cranium than from the bones of the base of the cavity. The adhe- 

 sions to the vault of the cranium are most firm along the lines of the sutures. This 

 is due to the fact that during the period before the sutures are closed the outer layer 

 of the dura mater is directly continuous with the external periosteum, and, in conse- 

 quence of this condition during development, the connective-tissue connection is more 



FIG. 658. THE DURA MATEU ENCEPHALI OF THE BASE OF THE CRANIUM. 

 (After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.) 



POSITION OF CRISTA GALLI 

 < 'ii-<-tihn- smut \ 



\ \ 



Oircttliit- xinus 



PROCESS OF DURA IN FORAMEN C/tCUM 

 OLFACTORY BULB 



OPTIC NER VE \ 



ic vein 



'".* sinvs 



( -finm i-fiii/r iriffi ftir -,. 

 ri-h- nffoi-amen ovale 



ttiriiingeal 

 artery 



I/t/i'rtttil carotid ______ t 



arte.ry 



nl!> fti tlir internal ______ 



juijiilttr vein 



i.s-'>'rw sinus 

 Mustoid vein ----- "" 

 Vertebral artery 



OPTIC NE&VE 



M. 1. 177, /,.I 

 NERVE 



ABDUCENS 



M:I:VJ-: 



SUPERFICIAL 



PKTHtin.lL 



XI-:HVK 



xt:i:n: 



XK i; vi-: 



FOLD OF DURA MATER 



<,/:,! I, M: i:\-i-: 



VAllJ'X NERVE 



Afi'KfiSORY XI-:r.VE 

 UYPOGLOSSAL XKKVE 

 F1HXT SPINAL . 



abundant along these lines and some is even caught in the closure of the sutures. 

 Along the vault there are occasionally noticed small lymph-spaces between the bone 

 and the dura mater. The stronger adherence to the base of the cranial cavity is due 

 to the numerous foramina in the floor, through which all the larger cranial blood- 

 vessels and the cranial nerves pass, and the dura mater is continuous with the con- 

 nective-tissue investments of these as well as with the periosteum lining the foramina . 

 Also the floor of the cavity is more uneven than the vault, and the projections of 

 the bones here tend to increase the firmness of attachment. The weight of the 

 brain upon the floor probably contributes to the result. 



The inner surface of the inner layer of the cranial dura mater forms the outer boun- 

 dary of the subdural cavity. Except for the occasional delicate subdural trabeculsp 

 and the passage of blood-vessels and nerve-roots, this surface appears smooth and 



