858 



ORGANS OF SPECIAL SENSE 



connected -with the dural sheath of the optic nerve. As it covers thespheno- 

 niaxillarv ti?;sure its fibres are interwoven with smooth muscle, forming the orbital 

 muscle of Miiller. From its inner surface processes run into the orbital cavity, 

 separating the fat lobules. One imi)ortant process comes from the periorbita al)out 

 midway along the roof of the orbit, runs forward to the back of the ui)per division 

 of the lachrymal gland, and there splits, helping to form the gland-capsule: this 

 capsule is joined at its inner border by other periorbital bands coming off near the 

 upper orbital rim, and forming the suspensory ligament of the gland. On the 

 inner side of the orbit the periorbita sends fibrous processes to the trochlea of the 

 superior oblique, which keep it in position. On arriving at the lachrymal groove 

 the periorbita divides into two layers, a thin posterior one continuing to line the 

 bone forming the floor of the groove, whilst the thicker anterior layer bridges over 



Fig. 485. — Vertical Sectiox through the Eyeball and Orbit in the direction of 

 THE Orbital Axis, with Closed Eyelids. 



(Semi-diagrammatic. After Schwalbe, modified to show fasciae.) 

 Periorhita green; muscle-fascia red ; Tenon's capsule yellow. 



SKIN OF LOWER LID 



LOWER TARSUS 



Palpebral faaeia and 



ant. lamina of musole- 



fascia 



Orbicularis palpe- 

 brarum 

 Extension of sheath of 

 inferior rectus to 

 lower eyelid 



FORNIX CONJUNCTI 



Inferior oblique muscle, 

 cut across 



Posterior lamina of 

 muscle-fascia 



SUPRAVAGINAL SPACE CONTINUOUS 



WITH TENON'S SPACE 

 SPACE OCCUPIED BY ORBITAL FAT, PRO- 

 CESSES OF FASCIA SEPARATING THE 

 LOBULES AND ENCLOSING BLOOD- 

 VESSELS 



Inferior rectus 



SKIN OF UPPER LID 



UPPER TARSUS 



CORNEA 



Orbicularis palpe- 

 brarum 



UPPER R!M OF ORBIT, WITH 

 Splitting of periorbita 

 Upper or anterior insertion 



of levator palpebrae 

 Superior palpebral muscle of 

 FORNIX CONJUNCTIV/t [Miiller 



Connection betTveen levator 

 palpebrae and sup. rectus, 

 and fibres to conjunctiva 



PROCESS FROM PERIORBITA TO 

 CAPSULE OF LACHRYMAL GUND 



Superior rectus 



Levator palpebrae 

 superioris 

 Posterior lamina of muscle- 

 fascia lined by prolongation of 

 Tenon's capsule 



OPTIC NERVE 



the groove and the sac which lies in it, forming the limbs of the inner palpebral 

 ligament (page 867). 



Quite anteriorly, at the rim of the orbit, the periorbita sends off a membranous 

 process which aids in forming the fibrous tissue of the eyelids (orbito-tarsal liga- 

 ment, or palpebral fascia), and is itself continuous with the periosteum of the 

 bones outside the orbital margin. 



2. The orbital muscles are connected by a common fascia, which splits at their 

 borders and furnishes a sheath to each. Processes of this fascia give membranous 

 investments for the vessels and nerves (including the optic nerve), splitting similarly 

 to enclose them; these membranous processes also assist in separating the fat 

 lobules. Posteriorly, this fascia is thin and loose, and blends with the periorbita at 

 the origin of the muscles. Anteriorly, it becomes thicker and firmer, accompanies 

 the muscles to near tlie equator of the eyeball, and there divides into two lamina^ 



