Fig. 355. Development of general structural features of the spinal cord; the nuclei of 

 origin and nuclei of termination of cranial nerves associated with the myelencephalon. 

 (A-E) The formation of the central canal, dorsal median septum, dorsal median sulcus, 

 and ventral median fissure in pig embryos. Arrows in the dorsal part of the developing 

 nerve cord show obliteration of the dorsal part of the primary neurocoel by medial 

 growth of the lateral walls of the spinal cord. By this expansive, medial growth, the 

 dorsal median septum and the dorsal sulcus (fissure) are formed. Observe that the central 

 canal is developed from the ventral remains of the primary neurocoel after the obliteration 

 of the dorsal portion of the primary neurocoel has been effected. In diagrams C-E, the 



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