276 HUMAN PHYSIOLOGY CHAP. 



11. If the eyes cause discomfort, headache, or a dull 

 feeling about the head, consult an oculist. Never have 

 anything to do with the quack eye doctors or street 

 venders of spectacles. 



12. Alcohol congests and inflames the conjunctiva 

 and lids, impairs vision in acuteness and quickness, 

 and may produce changes in the lens, retina, and 

 optic nerve. 



13. Tobacco smoke irritates the delicate lining of 

 the eyes and blurs the vision. 



j 



SUMMARY OF THE MAIN POINTS 



1. Every sensory nerve brings impressions to the brain, 

 from which we gain a knowledge of our own bodies and of 

 the world about us. These impressions we call sensations. 



2. The impressions received from the internal organs give 

 us sensations of hunger, thirst, faintness, giddiness, discomfort, 

 fatigue, itching, burning, aching, shuddering, creeping, etc. 

 These are called general sensations. 



3. There are little touch corpuscles in the papillae of the 

 dermis which serve as end organs of touch. They are most nu- 

 merous on the tip of the tongue and on the ends of the fingers. 



4. The tongue, soft palate, and pharynx are supplied with 

 end organs of taste called taste buds. They give us sensations 

 of sweet, spur, bitter, and salt Taste guides in the selection 

 of foods and gives an added pleasure to eating. 



5. The mucous membrane in the upper part of the nose is 

 provided with nerve endings that form the end organs of smell. 



6. The ear is the end organ of hearing. It consists of the 

 external, middle, and internal ear. The external consists of 

 the concha and auditory canal ; the middle, of the drumhead or 

 tympanum, the chain of three bones stretching across a hollow 



