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A. FEW POINTS IX CONNECTION WITH 



body. How, then, can they be of any use to the organism as 

 regards obtaining food for it, directing its movements, avoiding 

 dangers, etc., situated, as they are, in a strong, dark, bony case, in 

 the most protected of all parts of the body? To understand this, 

 we must revert for a few moments to the study of embryology or 

 the development of the body. Every human being begins life as 

 a single, round, nucleated cell (Fig. 6, A), measuring not 2 mm. in 

 diameter ; and this cell must be endowed with all the living pro- 

 perties of the future adult body in a primitive condition, for from 



Fig. 6. — Em bryological changes in Epiblast Cells, showing development 

 of Central Nervous System from surface cells (diagrammatic). 



A, Ovum. £, C, D, Segmentation or multiplication of cells. 

 E, Surface layer or Epiblast. F, Dipping down of E to form Central 

 Nervous System. G, Tube of Epiblast, cut off. H, Diagram of con- 

 nection in adult between brain-cells and surface-cells by nerve-fibres. 



it all the other cells are formed. It soon divides and multiplies 

 (Fig. 6, B and C) till the single cell becomes a mass of cells like 

 a mulberry (Fig. 6, D) in appearance. 



