MENTAL DEVELOPMENT 461 



The neurone is a complex cell behaving like a living 

 organism ; it nourishes itself and is not nourished. Now the 

 neurones forming the grey matter of the cortex are the most 

 complex and latest developed ontogenetically and phylogeneti- 

 cally, consequently the germinal determinants of these cells are 

 less fixed and stable, therefore more likely to undergo patho- 

 logical mutations than other cells of the body under the influence 

 of chronic poisoned conditions of the blood of the parents. 

 Whether this be so or not, it is certain that these cells are the 

 latest to mature and become capable of active employment, thus 

 they are more susceptible to arrest of growth, and development 

 by prenatal and postnatal nutritional failure, or by poisoned 

 conditions of the blood. Various forms of failure of develop- 

 ment of the brain occur owing to the lack of innate capacity or 

 specific energy of the neurones to grow, and since the brain 

 does not grow the skull-bones also fail to grow, and we have 

 what is termed a microcephalic idiot. It was at one time 

 thought that the brain was prevented from growing by the 

 closure of the bones of the skull, and surgeons attempted to 

 remedy this by removing pieces of the skull so as to allow the 

 brain space to grow ; but experience proved that the operation 

 did not cause the brain to grow and the operative treatment of 

 microcephalic idiocy was given up. A little reflection and ob- 

 servation would have shown that the brain is the master tissue 

 and determines the growth of the skull, and the reason why the 

 skull closed early was the natural response to the cessation 

 of the dynamic force of growth of the nervous structures of the 

 brain. I have already alluded to the fact that all the tissues of 

 the body will suffer in order that the brain may grow ; in starva- 

 tion the brain hardly loses any weight. The brain weight of 

 infants dying of exhausting diseases does not seem to suffer, 

 and the experiments of Donaldson at the Wistar Institute 

 (already alluded to in the previous lecture) show that imperfect 

 nutrition does not lead to arrest of growth and development of 

 the brain. An inborn germinal lack of capacity of the neurones 

 forming the anatomical basis of mind to develop and function 

 properly cannot be remedied by improved nutrition of the body, 

 and this is shown by the fact that mental deficiency is found in 

 children of all grades of society ; in fact, the majority of cases of 

 feeble-minded children are ineducable because of an inborn 

 physiological deficiency. 



