6io SCIENCE PROGRESS 



known ; its converse power to check and to call halt has only 

 recently become recognised and studied. Reflex inhibition is 

 the expression of this latter power. It is a great factor in the 

 due grading of muscular contraction. It grades the degree of 

 contraction of muscles in their execution of a particular act 

 under particular combinations of circumstances. It avoids waste 

 of nervous and muscular energy in the correlation of action of 

 antagonistic muscles. In the sequence of reflexes of opposed 

 effect it secures co-ordination by suppressing a pre-existent 

 reflex to make room for a new one which employs the muscles 

 differently. It plays an eminent part in the production of 

 rhythmic refractory phase, thus cutting a continuous reaction 

 into a series of intermittent ones ; in this way it evolves 

 alternating movements, e.g. stepping, from a tonic posture, e.g. 

 standing. Lastly, it induces discharge as an after-effect. It 

 interconnects the phases of diphasic reflexes by post-inhibitory 

 rebound. 



In all these uses of inhibition we see it as an associate of, and 

 a counterpart or counterpoise to, excitation. Whether we study 

 it in the more primitive nervous reactions which simply inter- 

 connect antagonistic muscles or in the latest acquired reactions 

 of the highly integrated organism, inhibition does not stand alone 

 but runs always alongside of excitation. In the simple correla- 

 tion uniting antagonistic muscle-pairs, inhibition of antagonist 

 accompanies excitation of protagonist. In higher integrations 

 where, for instance, a visual signal comes by training to be 

 associated to salivary flow, the key of the acquiring of the 

 reflex and of its maintenance is attention. And that part of 

 attention which psychologists term negative, the counterpart 

 and constant accompaniment to positive attention, seems as 

 surely a sign of nervous inhibition as is the relaxation of an 

 antagonist muscle, the concomitant of the contraction of the 

 protagonist. In the latter case the co-ordination concerns but 

 a small part of the mechanism of the individual and is spinal 

 and unconscious. In the former case it deals with practically 

 the whole organism, is cortical and conscious. In all cases 

 inhibition is an integrative element in the consolidation of the 

 animal mechanism to a unit3^ It along with excitation composes 

 a chord in the harmony which the health}^ working of the 

 organism exhibits always. 



