THE 



M-:U\ /; 



1041 



work separating the bundles of nerve-fibres: bet \\een the enclosed nerve-li 

 and each niesh of this framework there is a narrow interval occupied by hmph. 

 'I he nerve-fibres: are inediillated, luit have no primitive shea! h. . \liout lifieen or 

 twenty niilliinetres liehind the globe the central vessels enter, piercing obliquely 

 the lower outer quadrant of the nerve, and then run forwards in n I'hey are 



I'm ?:>!>. Ti; \\s\p .\ TMitoriiii Oi-ne NK,U\K, SIKIUIM; TIIK HKLATIONS OF 



1 1 > SHEATHS AND CON M.. i m. HSBDl I I;\MI 



DURAL SHEATH 



ARACHNOIOAL SHEATH 



^Bfl ^^^^~ft J ^ i^f f^^J^f^* "* ^^ Jt ^~"^L. ''^I^H^ 



SUBARACHNOID SPACE 



SUBOURAL SPACE 



( '< ntrtil retinal artery 

 Central retinal vein 



PIAL SHEATH 



Conncctlve-tiMue frame- 

 work, with ttieahea In 

 which the nerve-fibre 



bundles lie 



accompanied throughout by a special process of the pial sheath, which forms a 

 iil irons cord in the centre of the nerve. 



On reaching the eyeball, the dural sheath is joined by the arachnoid, and turns 

 away from the nerve to be continued into the outer two-thirds of the sclerotic. 

 Similarly the pial sheath also here leaves the nerve, its greater part running into 

 the inner third of the sclerotic, while a few of its fibres join the chorioid; the inter- 



Fio. 740. LONGITUDINAL SECTION THUO-UGII TERMINATION OF OPTIC NERVE. 



CHOfl : 



Short j' 



- PHYSIOLOGICAL PIT 



RETINA 



PIGMENT EPITHELIUM 

 8UPRACHORIOIOAL SPACE 



LAMINA CRI6ROSA 

 SCLEROTIC 



</ rrsxrlt 



DURAL SHEATH 



PIAL SHEATH 



ARACHNOIDAL SHEATH 



II I I'll 77N 

 CONUKCTIYK. 

 TIS& 

 FRAMEWORK 



:; 



vaginal space consequently ends abruptly in the sclerotic around the nerve-entrance. 

 In this locality the connective-tissue framework of the nerve becomes thicker and 

 closer in its mesh work, and has been already alluded to as the lamina cribrosa. It 

 is formed by processes passing out from the central fibrous cord at its termination 

 and by processes pass'mu; inwards from t he pial sheath, sclerotic, and chorioid. It does 

 not pass straight across the nerve, but follows the curve of the surrounding sclerotic, 

 66 



