I 



NEUEO-MUSCULAR MECHANISM 105 



developments of neurons, special receptors, have been evolved 

 which react more particularly to each of these special kinds of 

 change. With these peripheral neurons particular parts of the 

 central nervous system are connected and associated, so that 

 a special reaction to each of the various kinds of stimuli may 

 occur. These reactions may be accompanied by changes in the 

 consciousness by sensations; and since our consciousness is 

 our instrument of knowledge our Ego these sensations 

 appear to us the chief and most important part of the action 

 of the mechanism, and hence their activities are often considered 

 as The Senses. That, in many reactions, sensation is not an 

 essential part, we have already indicated. Most of our know- 

 ledge of the senses has necessarily been gained by observation 

 and experiment on the human subject, and it is perhaps 

 unjustifiable to assume that the results obtained can be applied 

 to lower animals. We know that in certain animals certain 

 receiving mechanisms are specially developed, while in others 

 other mechanisms are of chief importance. But how far the 

 activity of these mechanisms affects the consciousness it is 

 impossible to say. 



A. INTERO-CEPTIVE MECHANISM 

 Common Sensibility 



Throughout the internal organs are various peripheral 

 terminations of ingoing nerves, some apparently of the nature 

 of simple dendritic expansions, some of dendritic expansions 

 enclosed in definite fibrous capsules (Pacinian Corpuscles), 

 which are called into action by different kinds of stimulation, 

 nocuous and innocuous, to produce reflex adjustments of the 

 bodily mechanism either without or with the involution of 

 consciousness that is, either without or with the production of 

 sensation (see p. 96). Thus when food is taken into the stomach 

 it stimulates the ends of the different nerves, and these carry the 

 impulse up to the central nervous system to produce a reflex 

 dilatation of the gastric blood vessels. 



When the consciousness is involved in the action of these 

 mechanisms the sensations experienced are generally vague and 

 difficult to describe, and have been grouped under the term of 

 Common Sensations. The ordinary sensations of thirst and 



