THE CAUSE OF POSTUKES. 165 



opposite conditions of the nerve-mechanism pro- 

 ducing the postures of a joint, the postures will 

 be opposite or antithetical;" e.g. in a weak or 

 inactive condition of the nerve-mechanism govern- 

 ing the wrist, flexion results ; this would lead us to 

 anticipate that in an excited condition of this piece 

 of nerve-mechanism we should find the wrist 

 extended. 



The postures of a limb depend in their immediate 

 mechanism upon the resultant action of opposing 

 muscles, the relative tone of the antagonistic flexors 

 and extensors, the adductors and abductors, etc. 

 Various views may be held with regard to the 

 nerve-mechanism which regulates the contraction of 

 opposing sets of muscles. That mechanism may be 

 considered a line of reflex action regulating the 

 action of the muscles, or the balance may be con- 

 sidered due to some other kind of nerve-mechanism. 

 In any case it will, I think, be granted that some 

 portion of the- central nerve-system is the cause of 

 that balance of the muscles that produces the 

 posture, and therefore the posture is an index of 

 the condition of that central nerve-mechanism. 



In examining the condition of the nerve-system 

 in children, it has for several years been my habit 

 to observe what spontaneous posture would be 

 assumed by the hand when the forearm was held 

 out.* Let a weak, nervous child be requested to 

 hold out her hands in front on a level with the 

 shoulder in a prone position. The limb is now 



* See " Brain," part xi. ; and British Medical Journal, De- 

 cember 6, 1879. 



