THE PRINCIPLE OP THE DIRECT CHAP. Ill- certain sensations, desires, &e., are still performed analogous circumstances through mere habit althougi3- of no service. We have combinations of this kind? at least; in part, in the frantic gestures of rage and in the writb.— ings of extreme pain; and, perhaps, In the increased ac- tion of the heart and of the respiratory organs. Even when these and other emotions or sensations are arousecL in a very feeble manner, there will still he a tendencv to similar actions, owing to the force of long-associated habit; and those actions which are least under voluntary control will generally be longest retained. Our seeoncl principle of antithesis has likewise occasionally come Into play. Finally, so many expressive movements can be ex- plained, as I trust will be seen in the course of this volume, through the three principles which have now been discussed, that we may hope hereafter to see all thus explained, or by closely analogous principles. It Is-, however, often impossible to decide how much weiglrfc ought to be attributed., in each particular case, to one of our principles^ and how much to another; and very many points in the theory of Expression remain inex- plicable.