CHAPTER XII. 



ARCHITECTURAL CHANGES DUE TO GROWTH. 



Causes of change due to growth Size and organisation not neces 

 sarily connected Polarity of cells Significance of neuron 

 Meaning of medullation Formation of gyri Medullation in 

 cerebellum Growth of cerebellar cortex Development of 

 human cortex Source of cells in developed cerebral cortex 

 Observations by Vulpius Observations by Kaes. 



FROM what has been stated already, it is evident that 

 the architecture of the nervous system in the young 

 must be different from that in the adult, yet thus far the 

 structure at maturity has alone been described. The 

 possible causes of the changes due to growth may be 

 classed under four heads : alterations in the number of 

 the elements ; their size ; their organisation ; and their 

 nutrition. Since the central system is here considered 

 only after the total number of cell elements has been 

 formed, no variation due to this factor occurs. On the 

 other hand, the alterations in nutrition due to age are 

 so inadequately known, that in the absence of other 

 evidence, nutritional conditions from the standpoint of 

 the individual cell must be assumed to grow steadily 

 worse from birth on. There remain, therefore, as impor- 

 tant causes, the variations in the size and shape of the 

 elements, together with those changes in their relation 

 to one another which lead to differences in organisation. 



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