CAVITY <>!' Till-: 



lu:;:, 



of tho Ixxly of the sphenoid hone one or two millimetres in front of the origin of 

 the internal rectus. 



The four recti muscles lie rather close to the corresponding orbital walls for the 

 first half of their course, the supenor reel us, however, lieing overlapped in part hv 

 the levaior palix-hra-: they then turn towards the eyehall, running ol>liquely through 

 the orhital fat, and are finally inserted hy hroad. thin tendons into the sclen 

 in front of the equator. l''roln their respective positions in the orhit , t he a\ 

 this cone of muscles is ohlique to the anlero-posterior axis of the eyehall. The 

 thickest of these muscles is the internal red us. next the external, I hen the inferior, 

 and the su]>erior rectus is the thinnest. As regards length, the muscular helly of 

 the Superior reetus has the longest course, and the others diminish in the order - 

 internal, external, and inferior reetus. The external reetus is supplied by the sixth 

 nerve. The other three recti muscles are all supplied by the third nerve. 



The levator palpebras superioris courses along the roof of the orbit close to 

 the periosteum for the greater part of its course, partially overlapping the superior 



Km. 733. SECTION THROUGH CONTEXTS OF RIGHT ORBIT 8-11 MM. BEHIND THE EYEBALL, 

 VIEWED i UOM BEHIND. (After l.ange.) 



ST/V.M oKtur.ir. \i-:/: VK 



Levator palpebrae superioris 

 muscle 



Superior reel 

 muscle 



Superior oblique 

 inuBole 



Internal rectus 



muscle 



t '//;< 

 Centr,: 



artery 



Inferior reotus 

 muscle 



OBLK/ri: 

 MUSCLE) 



reetus; it finally descends through the orbital fat, and widens out to be inserted 

 into the root of the up]>er lid. It may he briefly described as being inserted fa two 

 distinct layers separated hy a horizontal interval. The upper or anterior layer of 

 insertion is fibrous, and passes in front of the tarsus, where it comes into relation 

 with fibres of the orhicularis. The lower layer consists of smooth muscle (Miiller's 

 superior tarsal muscle), and is inserted along the upper border of the tarsus. The 

 levator has also connections with the sheath of the superior rectus. These dif- 

 ferent insertions of the muscle will he referred to later along with the description 

 of the orhital fascia' and of the upper eyelid. It gets its nervous supply from the 

 third nerve, but the smooth muscle develojK'd in its lower layer of insertion is sup- 

 plied by the sympathetic nervous system. As its name expresses, ks action is to 

 raise the upper lid and to support it while t he eve is ojx'ii. 



The superior oblique runs forwards close to the inner part of the orbital roof 

 until it reaches the fossa trochlearis near the internal angular process, where it. 

 becomes tendinous and passes through a fibro-eartilaginous pulley attached to the 



