SPONTANEOUS POSTURES. 



the nerve-centres, and which we cannot at present 

 classify as either reflex or voluntary. The postures 

 assumed in an infant, who probably at birth has 

 no volition, are spontaneous if they are not reflex. 

 Postures in the adult are termed spontaneous if 

 they are not known to be either reflex or voluntary, 

 i.e. accompanied by consciousness. Postures assumed 

 by the subject when unconscious, as from the in- 

 fluence of chloroform, may be said to be spontaneous, 

 the outcome of the action of the nerve-mechanism. 



The postures that we see assumed under various 

 emotions, when we have evidence that they are not 

 purposely assumed, are indications of the action of 

 the nerve-centres ; hence the value of the study of 

 postures in children, whose movements are often so 

 little the result of self-consciousness, and are so 

 commonly purely spontaneous. 



In certain other cases postures are not indications 

 of the condition of the nerve-system. Postures of 

 the hand are often due to chronic changes in the 

 joints, the ends of the bones which are in apposi- 

 tion becoming changed as the result of disease, and 

 the ligaments so thickened and contracted as to 

 interfere greatly with the action of the muscles 

 upon them. If the muscles cannot freely move the 

 joints, the stimulus from the nerve-centres cannot 

 be accurately expressed by the postures of the 

 limb. In many cases of crippling rheumatism 

 the postures are caused by the local joint condi- 

 tion and indicate the state of the joints, not the 

 condition of the nerve-centres. So also diseased 

 conditions of the muscles may prevent expression 

 by nerve-muscular signs. 



