162 



THE SENSES. 



nasal cavity by the lachrymal duct. This secretion is slightly 

 alkaline, and contains about 1 per cent, of solids, chiefly sodium 

 chloride. 



What are the Meibomian glands? 



They are a number of small racemose glands, lying beneath the 

 conjunctiva, which secrete an oily protective substance. The ducts 

 of these glands open along the edge of the lid. 



Describe the eyeball. 



It consists of a tough, opaque globe (Fig. 47), having a some- 



FIG. 47. 



Horizontal Section of the Eight Eyeball: 1, optic nerve; 2, sclerotic coat; 3, cornea; 

 4, canal of Schlemm ; 5, choroid coat; 6, ciliary muscle; 7, iris; 8, crystalline lens; 

 9, retina; 10, hyaloid membrane: 11, canal of Petit; 12, vitreous body. 



what more sharply-curved translucent portion, the cornea, at the 

 front. It has in the anterior portion a lens, and in front and 

 behind this are chambers which contain fluids : the one in front is 



