HINOBRAIN 



OPHTHALMIC 

 BRANCH OF 

 NERVE! 



MAXILLARY 

 BRANCH OF 

 NERVE 1 



Fig. 357. External morphological development of various vertebrate brains. (A) 

 Diagram showing the fundamental regional cavities of the primitive five-part vertebrate 

 brain. (B-G) External morphological changes of the developing human brain and 

 cranial nerves. (Redrawn, somewhat modified, from Patten, 1946, Human Embryology, 

 Philadelphia, Blakiston, adapted primarily from Streeter and reconstructions in Car- 

 negie Collection.) (B) 20 somite embryo, probably 3!/2 weeks. (C) 4 mm. embryo, 

 about 4 weeks. (D) 8 mm. embryo, about 5V3 weeks. (E) 17 mm. embryo, about 

 7 weeks. (F) 50-60 mm. embryo, about 11 weeks. The brain now begins to assume 

 the configuration shown by the chick at hatching (see Fig. 347L and M). Roman nu- 

 merals III, IV, V, VI, VII, IX, X, XI and XII indicate cranial nerves. See Fig. 356A 

 and B for functional components of the cranial nerves at this time. (G) Lateral 

 view of brain at about the ninth month. (H, I, and I') Adult form of the brain of 

 Squalus acanthias. It is to be observed that the brain of Squalus acanthias loses the 

 marked cephalic flexure (see Fig. 347A) present in the early embryo, and assumes a 

 straightened form during the later stages of its development. (H and I ventral and dorsal 

 views, respectively, drawn from dissected specimens; I' redrawn and slightly modified 

 from Norris and Hughes, 1919, J. Comp. Neurol., 31.) (J and K) Ventral and dorsal 



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