Page:Mind (New Series) Volume 12.djvu/72

58 W. G. SMITH : ANTAGONISTIC REACTIONS. is innervated, there is a simultaneous inhibition of the muscle opposed to it. This law is not in conflict with the fact of prior innervation of the antagonistic muscle : in fact the two sequent processes of innervation and inhibition work together to the same result and tend to secure the more effective per- formance of the final movement. Looking at the problem from the psychophysical point of view we have to note that, in the interval immediately pre- ceding the reaction, the idea dominant in consciousness is that of holding the finger pressed down on the key. Now it is quite conceivable that the excitation caused by the stimulus, acting as a sort of shock (to use the expression applied to sensorial reaction by one of the subjects), should in certain cases first of all and most easily cause a more decided realisation of the motor idea already holding pos- session of consciousness, in other words, an increase in the innervation of the muscles which are already in a state of tension. We have an instance of this sort of action in the behaviour of certain patients suffering from general paralysis, of the insane whom I have had the opportunity of observing. They were directed to react in the ordinary way to the tap of a telegraph key and they carried out the direction. But when the chronoscope, standing close by, was started there was observed a sudden increase in the tension of the arm which was to take part in the reaction movement. It is, further, possible that the phenomena of antagonism have certain relations, in some individuals, to the alternation of impulses of which we are conscious in deliberation, hesitation and doubt. The physiological and psychophysical views of the phen- omenon, though divergent, are not in opposition. The first is in general preferable, for it rests upon precise experimental data, but it is probable that the latter view gives a truer account of the process in certain instances : it is also pos- sible that the different tendencies may sometimes support each other. More detailed experimental investigation will doubtless contribute to the understanding of the factors involved. There can be little doubt that further study of the phenomena of reaction by similar methods w T ill lead to interesting results. Variations in the length of reaction time are usually dealt with merely in their bearing on the trustworthiness of the average value. But if we were better acquainted experimentally with the many elements which enter as determining factors into these variations, we might be able to make a much more extensive use than we can do at present of the reaction process as an index of the activities of the central nervous system.