476 THE HUMAN BOD Y. 



loose in its socket; and then we get two sensations on 

 touching its free end with a foreign body. 



This irresistible mental tendency to refer certain of our 

 states of feeling to causes outside of our Bodies, and either 

 in contact with them or separated from them by a certain 

 space, is known as the phenomenon of the extrinsic refer- 

 ence of our sensations. 



The discussion of its origin belongs properly to Psychol- 

 ogy, and it will suffice here to point out that it seems largely 

 to depend on the fact that the sensations extrinsically referred 

 can be modified by movements of our Bodies. Hunger, 

 thirst, and toothache all remain the same whether we turn 

 to the right or left, or move away from the place we are 

 standing in. But a sound is altered. AVe may find that in a 

 certain position of the head it is heard more by the right 

 ear than the left; but on turning 'round the reverse is the 

 case; and half way round the loudness in each ear is the 

 same. Hence we are led, by mental laws outside of the 

 physiological domain, to suspect that its cause is not in our 

 Body, but outside of it; and depends not on a condition of 

 the Body but on something else. And this is confirmed 

 when going in one direction we find the sound increased, 

 and in the other that it is diminished. This implies that 

 we have a knowledge of our movements, and this we gain 

 through the ^muscular sense. It constitutes the reactive side 

 of our sensory life, associated with the changes we prodtrce 

 in external things; and is correlated and contrasted with 

 ttej^sive~si(Ierin which other things produce sensations 

 by acting upon us. 



As regards our common sensations we find something of 

 the same kind. The more readily they can be modified by 

 movement the more definitely do we localize them in space, 

 though in this case within the Body instead of outside it. 

 Hunger and nausea can be altered by pressure on the pit 

 of the stomach; thirst by moistening the throat with water; 

 the desire for oxygen (respiration-hunger) by movements of 

 the chest; and so we more or less definitely ascribe these 

 sensations to conditions of those parts of the Body. Other 

 general sensations, as depression, anxiety, and so on, are not 



