254 HUMAN PHYSIOLOGY CHAP. 



aware of the object. We become conscious of a sensa- 

 tion. 



172. General Senses. Many sensory nerves come 

 from the internal organs, as the stomach, intestines, 

 lungs, kidneys, heart and blood vessels, liver, etc. They 

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

 discomfort, fatigue, itching, burning, aching, shudder- 

 ing, creeping, and the like. These sensations do not 

 bring us any information of the objects about us, but 

 they do tell us something of the conditions of the vari- 

 ous organs. They tell us when we are to eat and drink, 

 when we are tired and sick, when we need sleep and 

 exercise, and a thousand other things important to health 

 and happiness. 



There are no special structures from which these 

 nerves start. They begin in free nerve endings and 

 give us general or common sensations. All other sen- 

 sory nerves come from the eyes, ears, nose, mouth, and 

 skin, and give us the special sensations. We shall now 

 study the special sense organs. 



173, The Sense of Touch. The true skin has little 

 projections called papilla, quite close together. In 

 these papillae there are peculiar little end organs in 

 which sensory nerves of touch begin. These end organs 

 occur in the tongue, in the mucous membrane of the 

 mouth and lips, and in the skin all over the body ; they 

 enable us to feel. They are most numerous on the tip 

 of the tongue and in the ends of the fingers, and fewest 

 on the middle of the back. 



When these end organs are stimulated by objects, we 



