CENTRAL NERVOUS SYSTEM 



533 



Figs. 703 to 709. — The Brains of Vertebrates 

 (after Biitschli, Gaupp, Crosby, Clark, Kuenzi and Sisson). 



Fig. 703.— a Cyclo- 

 s'tome : the lam- 

 prey, Petromyzon. 



Fig. 704.— a Sela- 

 chian : the shark, 

 Scymnus. 



Fig. 705. — An Am- 

 phibian : the frog, 

 Rana. 



Fig. 706.— a Rep- 

 tile : the alligator. 



Fig. 707. — A Bird: the Fig. 708. — A lower Mammal : Fig. 709. — A higher Mam- 

 goose, Ayiser. the Insectivore, Gymnura. mal : tlie horse, Equus. 



C, cerebrum ; Cb, cerebellum ; D, diencephalon ; MO, medulla oblongata ; 

 OB, olfactory bulb ; OL, optic lobe ; 01. L, olfactory lobe ; P, pineal complex ; 

 Q, corjjora cjuadrigemina ; F, ventricle of mid-brain ; V^, third ventricle ; V^, 

 fourth ventricle. 



The hind-brcmi essentially continues the segmental functions of the 

 cord, acting as a reflex centre for most of the head-region through the cranial 

 nerves, both sensory and motor, but in addition it assumes integrating 

 functions for such general autonomic activities as circulation and respiration 

 and the control of equilibration and posture. The last is subserved by 

 vestibular centres upon which the cerebellum is built as an integrating centre, 

 linking up the vestibular centres with the sensory organs mediating these 



