372 



ZOOLOGY. 



Attached to a downward prolongation (infundibulum) of the 

 optic thalami is the curious pituitary body. The medulla 

 sends nerves to the skin and muscles, giving sensibility and 

 motion to the face, eyes and nose, to the larynx and sensitive 

 portion of the lungs ; a pair also is sent to the lungs and 

 heart. If tlie spinal marrow is severed, the parts below are 

 paralyzed , if the medulla is cut or broken up mammals die 

 at once, while the lower Vertebrata die sooner or later. 

 The brain in an embryo originally consists of three vesi- 

 cles or primitive lobes ; and the correspondence between 



Pn. 



F--ZZT 



Fi" 367. "Diagrammatic, longitudinal and vertical section of a Vertebrate brain. 

 Mb mid brain ; what lies in front of this is the fore brain, and what lies behind, the 

 hind brain. L, lamina terminalis ; Olf, olfactory lobes ; limp, cerebral hemi- 

 spheres ; Th E, thalamencephalon ; P, pineal gland ; Py, pituitary body ; FM, fo- 

 ramen of Munro ; ('#, corpus etriatum ; 7%, optic thalamns; CQ, corpora quadri- 

 gemiua ; CO, crura cerebri : Ob, cerebellum ; PV, pons varolii ; M 0, medulla oblon- 

 gata ; /, olfactorii ; II, optici ; ///, point of exit from the brain of the Motores 

 oculorum ; IV, of the pathetic! ; T7, of the abdncentes ; V-XII, origin of the other 

 ci'.-ebral nerves ; 1, olfactory ventricle; 2, lateral ventricle ; 3, third ventricle; 4, 

 fourth ventricle. After Huxley. 



the three primitive lobes, called respectively the fore, mid, 

 and hind brain, may be seen by the following table : 



TABULAR VIEW OF THE SUBDIVISIONS OF THE VERTEBRATE BRAIN 



Olfactory lobes or ganglia, with their ventricles (rhinen- 



cephalon). 

 Cerebrum < r cerebral lobes or hem'spheres (with the 



two lateral or first and second ventricles, forming 



the prosencephalon or prothalami). 

 Optic thalami, with the third ventricle and conarium 



above uiid hypophysis (pituitary body) below 



(Thalamencephalon pineal gland). 



Fore brain. 



