THE ORBIT 259 



enters the orbit through the interval between the heads of 

 lateral rectus muscle, and it supplies the lateral rectus only. 



Musculus Obliquus Inferior. The inferior oblique muscle 

 arises from a small depression on the orbital surface of the 

 maxilla, immediately lateral to the opening of the naso- 

 lacrimal duct. It passes laterally, below the inferior rectus 

 muscle, and, inclining slightly backwards, ends in a thin 

 membranous tendon, which gains insertion into the lateral 

 aspect of the sclera of the eyeball under cover of the rectus 

 lateralis. The insertion is not far from that of the superior 

 oblique. The inferior oblique is supplied by the inferior 

 division of the oculo-motor nerve. It turns the eyeball so that 

 the centre of the cornea is directed upwards and laterally. 



Fascia Bulbi (O.T. Capsule of Tenon). The connections 

 of the fibrous sheath of the eyeball are somewhat com- 

 plicated, and they cannot be satisfactorily displayed, in every 

 detail, in an ordinary dissection. The fascia may be studied 

 from a threefold point of view (i) in its connection with 

 the eyeball; (2) in its connections with the muscles inserted 

 into the globe of the eye \ and (3) in its connections with 

 the walls of the orbit. 



The relation which the fascia bulbi bears to the eyeball 

 is very simple. The membrane is spread over the posterior 

 five-sixths of the globe the cornea alone being free from it. 

 Anteriorly, it lies in relation with the ocular conjunctiva, with 

 which it is intimately connected, and it ends by blending 

 with the conjunctiva close to the margin of the cornea. 

 Posteriorly, it fuses with the sheath of the optic nerve where 

 the nerve pierces the sclera. The internal surface of the 

 membrane (i.e. the surface towards the globe of the eye) is 

 smooth, and is connected to the eyeball by some soft, yielding, 

 and humid areolar tissue, the interval between them con- 

 stituting, in fact, an extensive lymph space. Its external 

 surface is in contact posteriorly with the orbital fat, to which 

 it is loosely adherent ; and it is firmly attached to the ocular 

 conjunctiva more anteriorly. It obviously, therefore, forms 

 a membranous socket in which the eyeball can rotate with 

 the greatest freedom. 



The tendons of the various ocular muscles are inserted 



into the eyeball within the fascia bulbi, and they gain its 



interior by piercing the fascia opposite the equator of the 



globe (Fig. 98). The lips of the openings through which 



in 17 a 



