

CHAPTER XLI 



THE SPECIAL SENSES 



244. Function of Sensations. The greater part of our 

 tissues seem designed simply for the purpose of maintaining 

 the body as a living and healthy organism. The alimentary 

 canal serves for the digestion of food, the blood to carry the 

 digested food to the cells, the lungs to obtain oxygen by means 

 of which the muscles can release the energy in the food, and 

 the organs of excretion for the disposal of the wastes. All 

 these functions are characteristic of living things in general 

 and proceed automatically without the organism taking 

 thought of the matter; indeed many of the bodily processes 

 appear to go on as well when we are asleep as when we are 

 awake. There is, however, another faculty developed in the 

 body which we term consciousness and by means of which we 

 are made aware of our surroundings and are thus able to 

 enjoy existence. This faculty is located in the cerebrum 

 which forms the upper and forward part of the brain, It 

 communicates with the outer world through the nerves and 

 end organs, the latter located at various places on the exterior 

 of the body. The end organs, however, serve merely to re- 

 ceive and transmit sensations and have no part in the appre- 

 ciation of such sensations. This latter is a function of the 

 cerebrum alone. Some of the sensations coming to the brain 

 have no definite sense organs for their perception and they are 

 therefore called general sensations. In this group may be 

 included, hunger, pain, thirst, fatigue, satiety and various 

 others concerned in the upkeep of the body. Impressions 

 from the external world, however, are all perceived by special 



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