THE OUTER AND INNER WORLDS 215 



air, or have a feeling of the enjoyment of 

 life, such as one has in a state of health while 

 in the open air and in fine weather. As a 

 rule, we pay little attention to these internal 

 senses, which seem to be on the very thresh- 

 hold of feeling, but we are more or less con- 

 scious of them when they rise to a certain 

 intensity. Of many organs we are uncon- 

 scious, except when the nervous impulses 

 coming from them cause sensations that rise 

 to the level of pain. No doubt the nervous 

 centres are almost constantly receiving ner- 

 vous impulses which, although they may not 

 rise into the sphere of consciousness, yet fill 

 up, as it were, the interstices of our conscious 

 life and give it completeness. There do not 

 appear to be any special mechanisms for these 

 internal senses. The ordinary sensory or 

 centripetal nerves serve the purpose. 



125. But we become cognizant of the outer 

 world by the five external senses of vision, 

 hearing, touch, taste, and smell, and we 

 learn about our position and movements in 

 the outer world by nervous impulses concerned 

 in what is called the muscular sense, and in the 



