THE LACHRYMAL GLAND. 641 



the eve are six muscles four straight and two oblique ; and there is 

 also an elevator of the upper eyelid in the cavity. 



The nerves in the cavity are numerous, viz., the second, third, several era- 

 fourth, ophthalmic of the fifth, and the sixth, together with the small nial nerves ? 

 temporo-malar "branch of the superior maxillary nerve, and offsets of 

 the sympathetic : their general distribution is as follows : The 

 second nerve enters the eyeball ; the third supplies all the muscles their distri- 

 of the cavity but two ; the fourth enters the superior oblique ; and bution > 

 the sixth is spent in the external rectus muscle. The fifth nerve 

 supplies some filaments to the eyeball with the sympathetic, but the 

 greater number of its branches pass through the orbital cavity to the and some 

 face. The ophthalmic vessels are also contained in the orbit. vessels. 



The LACHRYMAL GLAND (fig. 227, F) secretes the tears, and is Lachrymal 

 situate in the hollow on the inner side of the external angular process SeJpart 

 of the frontal bone. It is of an oval form, something like a small f orbit, 

 almond, and measures about three-quarters of an inch in its longest 

 diameter, which is directed transversely. From its fore part a thin 

 accessory piece projects beneath the upper eyelid. The upper 

 surface is convex, and in contact with the periosteum, to which it 

 is connected by fibrous bands that constitute a ligament for the 

 gland ; the lower surface rests on the eyeball and the external rectus 

 muscle. 



The gland has from eight to twelve very fine ducts, which open on Ducts open 

 the surface of the conjunctiva in a curved line above the outer part behind 

 of the upper eyelid, and a little in front of the fornix. eyelid. 



The FOURTH NERVE (fig. 227, *) is the most internal of the three Fourth 

 nerves entering the orbit above the muscles. In the cavity, it is nerve 

 directed inwards above the levator palpebrse to the superior oblique supplies 

 muscle, which it pierces on the upper, or orbital surface. owftuT 



The OPHTHALMIC TRUNK of the fifth nerve as it approaches ophthalmic 

 the sphenoidal fissure, furnishes from its inner side the nasal branch, 

 and then divides into the frontal and lachrymal branches ; the 

 first passes into the orbit between the heads of the external rectus, 

 but the other two lie, as before said, above the muscles. 



The frontal nerve (fig. 227, 2 ) is close to the outer side of the fourth Frontal 

 as it enters the orbit, and is much larger than the lachrymal branch. 

 In the course to the forehead the nerve lies along the middle of the divides into 

 orbit ; and after giving off from its inner side the supratrochlear and^upra^ 1 

 branch ( 4 ), it leaves the cavity by the supraorbital notch. Taking the trochiear, 

 name supraorbital, it ascends on the forehead, where it is distributed. 

 This nerve frequently divides into its two main branches (p. 504) 

 while still within the orbit. 



While in the notch the supraorbital nerve gives one or two palpebral Paipebrai 

 filaments to the upper lid. 



The supratrochlear nerve ( 4 ) passes inwards above the pulley of the supra- 

 upper oblique muscle, and leaves the orbit to end in the eyelid and 

 forehead (p. 504). Before the nerve turns round the margin of the 

 frontal bone, it sends downwards a twig of communication to the 

 infratrochlear branch of the nasal nerve. 



D.A. T T 



