372 



ZOOLOGY. 



Attached to a downward prolongation (infandibnlum) of the 

 optic thalami is the carious 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 

 ieart. If the spinal mari'ow is severed, the parts below are 

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

 at once, vhile the lower Tertebrata die sooner or later. 

 The brain in an embryo originally consists of three vesi- 

 cles or primitive lobes ; and the correspondence between 



MB- 



IT 



Y'lg. 367.— jDiagrammatic, joniiiiudlnal and vertical section of a Vertebrate brain. 

 Jib, inid brain; whatlies in front of ihla is tbe fore brain, and what lies bebind, the 

 "bind brain. L, jamina terminalis ; Olf, olfactory lobes ; Hmp, cerebral hemi- 

 spheres; ThB, thalamencepbalon ; Pa, pineal gland ; Py, pitoitary body; Fif, fo- 

 Tiimen of Mnnro ; C'-S, corpus striatum; TA, optic thalamus; CO. corpora quadri- 

 gemina ; C(7, crura cerebri: Cb, cerebellum ; PF, pon:* varolii ; }{0, merlnlla oblon- 

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

 oculorum ; /F, of the pathetici ; VT,ot the abdncentes ; V-XZI^ origin of tbe other 

 cerebral 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 : 



Tabulab View of the StrBDivtsiONs of the Vertebrate BRArjr 



Fore brain. 



Olfactfiry lobes or ganglia, with their ventricles (rhinen- 



ceplialon). 

 Cerebrum < i cerebral lobes or liemapheres (with the 

 , two lateral or first and second ventricles, forming 



the prosencephalon or prothalami). 

 Optic thalami, with the third ventricle and conarium 

 above and hypophysis (pituitary body) below 

 ( (Tbalamencephalon pineal gland). 



