1072 



SPECIAL SENSE ORGANS 



larly 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 the equa- 

 tor of the eyeball, and there divides into two laminae, an anterior and a posterior; the former 

 continues a forward course, forming a complete funnel-shaped investment all around, passing 

 ultimately to the eyelids and orbital margin — whilst the latter turns backward, covering the 

 hinder third of the globe. 



The anterior lamina is a well-marked membrane everywhere, but in certain situations it 

 presents special bands of thickening, corresponding to the direct continuation forward of the 

 sheath of each rectus muscle. Above and below, this lamina spreads out in the form of two 

 large membranes, which are finally applied to the deep surface of the palpebral fascia; the lower 

 membrane constitutes what has been described as the suspensory hgament of the eyeball.' 

 The upper membrane requires a fuller description, as its distribution is modified by the presence 

 of the levator palpebrae muscle. 



Fig. 816. — Horizontal Section Through Left Orbit, viewed from above. 

 (After von Gerlach. To show check ligaments, etc.) 



Taisus 



Conjunctival fornix 

 Lacrimal gland 



Palpebral raphe 



Lateral check ligament i^ 



Lateral orbital wall 



Lateral rectus 

 Orbital fat 



M. Orbicularis palpe- 

 brarum 



\ \\( * ^^^ Space occupied by 

 \ \\\ > T-i subconjunctival tis- 

 '' 1 / sue, and by fascia 



bulbi further back 

 Upper part of Horner's 



muscle 

 Palpebral fascia 



Medial check ligament 



/ . - l/ht Spatium interfasciale 

 ^ Tj (Tenon's) 



Medial wall of orbit 



— -Optic nerve 



Medial rectus 



Ethmoidal cells 



The upper part of the sheath of the superior rectus (along with the adjoining membrane on 

 each side of it) passes to the deep surface of the levator, to which it closely adheres, and com- 

 pletely ensheaths this tendon by extending round its borders to its upper surface. The lower 

 part of this levator sheath is applied to the inferior surface of the deeper of the two divisions of 

 the levator muscle, superior tarsal muscle, and is attac^hed to the upper border of the tarsus of 

 the ui)pcr lid, reaching on each side to the lateral and medial angles of the orl)it. The upper 

 part of the sheatli of the superior tarsal muscle reaches to the middle of the palpebral fascia, and 

 is mainly continued forward between the muscle and the fascia to the anterior surface of the 

 tarsus. 



The lower membrane (suspensory ligament of the eyeball), joined by the sheath of the 

 inferior rectus, reaches forward to the attached (posterior) border of tiie tarsus of the lower lid, 

 where it is mainly attached, while a part of it extends to the lower pali)cbral fascia. 



To understand the special hands of the anterior himina mentioned above, we must follow 

 the sheath of each rectus muscle forward, when we find tiiat, while it is rather loosely applied 

 to the muscular Ixilly in its })ostcrior two-thirds, it tlien suddeidy l)ec()mes thicker, and is 

 firmly attached to the muscle for some distance! before finally leaving it, and is thereafter often 

 accomf)ariied l)y some muscle-fil)res. 'i'he l)est developed of these bands, the lateral check 

 ligavii III, passes ant(!riorly and laterally to tlu! lateral ungie of tli(> orbit, helping to support the 

 lacrimal gland on its way, and is inserted near the orbital edge immediately behind the 

 lateral palpebral raphe. Tlie medial l)aiid, or inedial check lif/anierd, is larger than the lateral, 

 but not so thick; it |)asses forward and medially to be in.serted into the upper part of the lacrimal 

 crest and just bcliind it. These two bands, lateral and medial, come from the sheaths of the 



