830 Muscular Movements in Man and their Evolution. [June 21, 



young seedling plants. It is argued that as circumnutation becomes 

 modified by external forces to the modes of movement termed 

 heliotropism, geotropism, &c, so microkinesis in the infant is replaced 

 by the more complicated modes of brain action as evolution proceeds. 



The conditions of movement are then described, as seen at succes- 

 sive stages of development of the child, and it is shown that they 

 become less spontaneous, and more under control of stimuli acting 

 upon the child from without, while the phenomena termed memory 

 and imitation are evolved. 



Section III. Properties of Nerve-centres and their Modes of Action. 



From observations made, descriptions are given of the modes of 

 action and properties of nerve-centres in adult age, such descriptions 

 being given in terms implying visible movements. Impressionability, 

 imitation, and retentiveness are thus described. Nerve-centres are 

 said to be " free " when only slightly stimulated. Delayed expression 

 of impressions are seen when the visible outcome is delayed after 

 the stimulus which produced it. Double-action is said to occur when 

 a local effect and a distant one, occur from one impression. Com- 

 pound cerebral action is said to occur, when the study of the visible 

 movements indicates that successive unions of centres are in action, 

 leading to a visible outcome well adapted to the primary stimulus 

 which produced the series. When a slight stimulus leads to a spread- 

 ing area of movements producing considerable force, the phenomenon 

 is termed reinforcement. 



From observations made, two hypotheses are put forward. It is 

 suggested that when a well co-ordinated movement follows a slight 

 stimulus, the impression produces temporary unions among the 

 centres, preparing them for the special combinations and series of 

 actions which are seen to follow. Such unions among nerve-centres 

 appear to be formed when a period of cerebral inhibition, produced 

 by a word of command, is seen to be followed by a co-ordinated series 

 of acts. A graphic tracing indicating suspension of microkinesis to 

 the stimulus of sight and sound is given. It is further suggested that 

 the brain action corresponding to thought, is the formation of func- 

 tional unions among cells, whose outcome is seen in the movements 

 which express the thought, or its physical representation. Properties 

 similar to those described in brain centres may be illustrated in 

 modes of growth. Intelligence is then not a property of the brain, 

 per se, but for its manifestation certain modes of brain action are 

 necessary. In the special postures and movements described, a 

 number of physical signs of brain states are offered to the clinical 

 observer. 



