THE NERVOUS SYSTEM. 



m .J? 



487 





m b a 



FIG. 420. 



FIG. 417. From the neural tube of an embryo rabbit shortly before the closure of the tube, g, Germi- 

 nal or dividing cell; m, peripheral zone, position of the later marginal layer. His. 



FIG. 418. Pig of 5 mm., unflexed Just after closure of the neural tube. Segment of a vertical 

 section of the lateral wall of the tube, g, Germinal cells; m, beginning of marginal layer; 

 mli, internal limiting membrane; r, radial columns of protoplasm. The resting nuclei lie in 

 the inner or nuclear layer. Hardesty. 



