CHAPTER X 



THE SPECIAL SENSES 



The Production of Sensations Variety o Sensations General Sensi- 

 bility Pain and its Function >S^^B^ Sensation, Touch, Taste, 

 Smell, Sight, and Hearing The Ha^fihe Organ of Touch The 

 Sense of Touch Delicacy of Touch -^flsation of Temperature and 

 Weight The Tongue, the Organ of^TtB The Nerves of Taste 

 The Sense of Taste and its Relations with the other Senses The 

 Influence of Education on the Taste The Nasal Cavities, or the 

 Organs of Smell The Olfactory Nerve The Uses of the Sense of 

 Smell The Sense of Sight .Light The Optic Nerve The Eye- 

 ball and its Coverings The Function of the Iris The Sclerotic, 

 Choroid, and Retina The Tears and their Function The Move- 

 ments of the Eyeball The Function of Accommodation The Sense 

 of Hearing and Sound The Ear, or the Organ of Hearing The 

 External, Middle, and Internal Ear 



1. Production of Sensations. We have already seen that the 

 true centre of sensation is some organ within the skull, proba- 

 bly among the gray masses at the base of the brain ; but the 

 mind never perceives impressions at that point; on the con- 

 trary, it always refers them to the external organs of sensa- 

 tion. Hence, it is convenient to say that those outer parts 

 possess the property of sensibility. For instance, we say that 

 we hear with the ear, taste with the tongue, and feel with the 

 fingers. That this is not the exact truth is proved by the fact 

 that, whenever the nerve connecting one of these organs with 

 the brain is severed, it at once loses its capacity for sensation. 



2. Consciousness, another faculty of the brain, is necessary 

 to complete a sensation. During sleep, and in other uncoii- 



1. True centre of sensation ? Place of the mind's impressions ? What is it convenient 

 to say ? What further is stated ? 



2. Consciousness ? During sleep ? In profound insensibility ? 



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