MUSCLES OF THE EYEBALL. 483 



such quantity as to be drained off into the nose, from 

 which they flow into the pharynx and are swallowed. 

 When the lachrymal ducts are stopped up, however, their 

 continual presence makes itself unpleasantly felt, and may 

 need the aid of a surgeon to clear the passage. In weeping 

 the secretion is increased, and then not only more of it en- 

 ters the nose, but some flows down the cheeks. The fre- 

 quent swallowing movements of a crying child, sometimes 

 spoken of as "gulping down his passion," are due to the 

 need of swallowing the extra tears which reach the pharynx. 



FIG. 123. The eyeballs and their muscles as seen when the roof of the orbit 

 has been removed and the fat in the cavity has been partly cleared away. On 

 the right side the superior rectus muscle has been cut away, a, external rec- 

 tus; s, superior rectus; i, internal rectus; t, superior oblique. 



The Muscles of the Eye (Fig. 123). The eyeball is 

 spheroidal in f orm and attached behind to the optic nerve, n, 

 somewhat as a cherry might be to a thick stalk. On its exte- 

 rior are inserted thelejidons of six muscles, four straight and 

 i^Q_oblique. The straigh t muscles lie, one (superior rectus), 

 s, above, one (inferior rectus} below, one (external rectus), 

 OijQi3aAA&&r^ the eyeball. 



Each arises behind from the bony margin of the foramen 

 through which the optic nerve enters the orbit. In the figure, 



