MENTAL DEVELOPMENT 303 



said that the cerebral hemispheres at birth only show staining 

 indicating preparedness for function in the base and stem of the 

 great brain. The structures which are stained in Plate V, 

 fig. 1 are the systems of neurones essential for the perform- 

 ance of the complex, automatic, co-ordinate movements of the 

 new-born child, viz. breathing, crying, sucking, swallowing. 

 Occasionally anencephalous monsters are born in which this is 

 the only portion of the brain present, the cerebral hemispheres 

 being absent. Such monsters are capable of breathing, crying, 

 sucking, and swallowing by the preorganised nervous mechanism 

 in the stem of the great brain which is present in these creatures. 

 The first appearance of myelin staining after birth is in the 

 regions about the primary fissures — the sensory afferent pro- 

 jection systems, the avenues of experience and intelligence; 

 later the motor efferent projection system is myelinated. You 

 observe that these several sensory perceptual centres of 

 vision, hearing, smell, taste, and tactile-motor perception are 

 independent. At this stage of development the child is capable 

 of experiencing a simple elemental sensation, but later as the 

 association neurones take on function as indicated by myelination 

 of their fibres, the independent perceptor centres are physio- 

 logically connected and functionally associated. That being the 

 case the child is no longer capable of a simple sensation. You 

 have only to watch an infant follow with its eyes a bright 

 object ; it makes very clumsy efforts at first, it does not 

 recognise what the object is ; but after a time and numbers of 

 experiments it learns to stretch out its hand to get it, and if it 

 succeeds it will take it to its mouth ; nutrition is its object. If 

 the spoon contains sugar the infant, having experienced the 

 pleasure of sweet taste, at the sight of the spoon exhibits 

 satisfaction and attempts to grasp it ; this means that the visual 

 centre has been associated with the motor centre and the 

 successive movements it makes successfully to grasp the spoon 

 cause sensory impulses from skin, muscles, tendons, and joints to 

 be registered in the sensory tactile-motor sphere, so that after 

 numerous experiences association for the eye and hand is 

 effected. Suppose the infant is subsequently given a powder 

 in the spoonful of sugar, the sense of taste and smell is 

 excited and disgust produced, with signs of nausea, spitting out, 

 and crying. A new experience has been made and the sight of 

 the spoon, instead of awakening pleasurable feelings, will arouse 



