288 



EXPEETMENTAL GENERAL SCIENCE 



or thinner and thus changing its curvature. The eye, being 

 one of the most delicate parts of the body, is appropriately 

 protected by a bony socket, eyelids and projecting eyebrows. 

 On the upper and outer side of the eye, is a tear gland which 

 supplies a watery fluid that serves to keep the eye moist 

 and free from dust. When one is under strong emotion, or 

 when the eye is irritated, the tear glands pour out an extra 

 amount of fluid which gathers in drops and overflows upon 



Retina 



Cornea 



- Ciliary processes 



Lymph canal 

 Ciliary muscle 



FIG. 96. A section of the eye. (Holden.} 



the cheeks. Ordinarily the surplus moisture is drained away 

 through a tiny tube into the nose. 



Practical Exercises 



1. Why do we sniff when we are attempting to locate a faint odor? 



2. Why does one smack his lips when carefully tasting a substance? 



3. Why may a substance first taste sweet and then bitter? 



