1024 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT 



inferior directing it upward and lateralward; these movements are required for the correct viewing 

 of an object when the head is moved laterally, as from shoulder to shoulder, in order that the 

 picture may fall in all respects on the same part of the retina of either eye. 



A layer of non-striped muscle, the Orbitalis muscle of H. Miiller, may be seen 

 bridging across the inferior orbital fissure. 



Optic nerve 



Fascia balbi 



- Cornea 

 Superior tarsus 



Inferior tarsus 



FIG. 891. The right eye in sagittal section, showing the fascia bulbi (semidiagrammatic) . (Testut.) 



The Fascia Bulb (capsule of Tenon) (Fig. 891) is a thin membrane which envelops 

 the bulb of the eye from the optic nerve to the ciliary region, separating it from 

 the orbital fat and forming a socket in which it plays. Its inner surface is smooth, 

 and is separated from the outer surface of the sclera by the periscleral lymph space. 

 This lymph space is continuous with the subdural and subarachnoid cavities, 

 and is traversed by delicate bands of connective tissue which extend between the 

 fascia and the sclera. The fascia is perforated behind by the ciliary vessels and 

 nerves, and fuses with the sheath of the optic nerve and with the sclera around the 

 entrance of the optic nerve. In front it blends with the ocular conjunctiva, and 

 with it is attached to the ciliary region of the eyeball. It is perforated by the 

 tendons of the ocular muscles, and is reflected backward on each as a tubular 

 sheath. The sheath of the Obliquus superior is carried as far as the fibrous pulley 

 of that muscle; that on the Obliquus inferior reaches as far as the floor of the 

 orbit, to which it gives off a slip. The sheaths on the Recti are gradually lost in 

 the perimysium, but they give off important expansions. The expansion from the 

 Rectus superior blends with the tendon of the Levator palpebrse; that of the 

 Rectus inferior is attached to the inferior tarsus. The expansions from the sheaths 

 of the Recti lateralis and medialis are strong, especially that from the latter muscle, 

 and are attached to the lacrimal and zygomatic bones respectively. As they prob- 

 ably check the actions of these two Recti they have been named the medial and 

 lateral check ligaments. Lockwood has described a thickening of the lower part 



