330 THE MORPHOGENESIS OF THE CENTRAL NERVOUS SYSTEM 



THE DERIVATIVES OF THE NEURAL TUBE 



Primary Vesicles 



Subdivisions 



Derivatives 



Cavities 





Telencephalon 



Cerebral cortex 

 Corpora striata 

 Rhinencephalon 



Lateral ventricles 



Cranial portion of 



third ventricles 



Prosencephalon 



Diencephalon 



Epithalamus 

 (pineal body) 



Thalamus 



Optic tract 



Hypothalamus 

 hypophysis 

 tuber cinereum 

 mammillare bodies 



Third ventricle 



Mesencephalon 



Mesencephalon 



Corpora quadrigemina 



Tegmentum 



Crura cerebri 



Aquaeductus cerebri 



Rhombencephalon 



Metencephalon 



Cerebellum 

 Pons 



Fourth ventricle 





Myelencephalon 



Medulla oblongata 





Spinal cord 



Spinal cord 



Central canal 



The Later Differentiation of the Subdivisions of the Brain 

 Myelencephalon. — We have seen that the wall of the spinal cord differen- 

 tiates dorsally and ventrally into roof plate and. floor plate, laterally into the basal 

 plate and alar plate. The boundary line between the basal and alar plates is the 



Roof plate 



Mantle 

 layer 



RooF plate 



5 ulcus I i mi tans 



Ependymal 

 layer 



Alar plate 

 S. limitans 



Basal plate 



Opinal 

 qanqlton 



Ventral spinal root 



Fig. 316. — Transverse sections. A, through the upper cervical region of the spinal cord in a 10 mm. 

 human embryo; B, through the caudal end of the myelencephalon of the same. X 44. 



sulcus limitans (Fig. 316 A.). The same subdivisions may be recognized in the 

 myelencephalon. It differs from the spinal cord, however, in that the roof plate 

 is broad, thin and flattened to form the ependymal layer (Fig. 316 B.). In the 

 alar and basal plates of the myelencephalon the marginal, mantle and ependymal 

 zones are differentiated as in the spinal cord (Fig. 317 A, B). Owing to the for- 



