MENTAL DEVELOPMENT 



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germinal determinants of the cortical neurones, whereby the 

 neuroblasts or primordial cells from which the neurones develop 

 may, in consequence of an inherited defect, be deficient in 

 numbers or deficient in specific energy, consequently they do 

 not grow and develop. " Like tends to beget like," and the 

 cause arises in most cases from defective progenitors. If one 



Fig. 3 — Diagram to illustrate the comparative architecture of the cortex, of the healthy 

 normal brain, of the brain of the feeble-minded (inborn amentia), and of the brain of 

 the dement who has lost his mind. 



Observe that the cells have lost their processes and are shrunken and irregular in form, also note the 

 comparative poverty of fibres especially of the horizontal association fibres in Amentia and Dementia. 



parent be feeble-minded, only some of the offspring will be 

 mental defectives. If both are feeble-minded, the chances are 

 the whole of the offspring may be more or less feeble-minded. 

 It was calculated by the late Dr. Ashby, a very experienced 

 children's physician, that 75 per cent, of the mental defectives 

 20 



