200 



AtflMAL PHYSIOLOGY. 



hemisphere-vesicles; while foremost of all are two olfactory 

 lobes or bulbs. In front of the medulla oblongata, on the 

 under surface, are two masses 

 placed close together with a slight 

 elevation between them, the hypo- 

 aria or inferior lobes, and imme- 

 diately in front of them the 

 pituitary body. The hypoaria lie 

 beneath the optic lobes; and, in 

 front of them, apparently arising 

 from the optic lobes, are the optic 

 nerves, which, as they pass for- 

 wards, cross one- over the other, 

 so that each supplies the eye of 

 the side opposite to that from 

 which it arises. 



In a turtle's brain there is no 

 difficulty in recognising the me- 

 dulla oblongata, cerebellum, optic 

 lobes, and olfactory bulbs, and the 

 olfactory and optic nerves; but 

 the hemisphere-vesicles are much 

 larger than in the cod. On open- 

 ing up the brain, the common 

 ventricle, prolonged forwards un- 

 derneath the cerebellum, is seen 

 to turn downwards, and terminate 

 in a cul-de-sac at the pituitary 

 body; and, above this point, it 



T^,. in/l -n bifurcates to extend through the 



Fig. 104. BRAIN OF A , . , . , 



TURTLE, opened along the hemisphere-vesicles and olfactory 

 right side, a, Cerebellum; bulbs. In the floor of each hemi- 

 &, optic lobe ; c, hemi- sphere- vesicle is a thickened part, 

 sphere; d olfactory bulb; th us striatu ' m . and in the 



e, pineal body;/, opening ., * ,, i . i 



into infundibulum, and, to <?% of tn ^ vesicle there is a 

 the left of that, the choroicl digitate vascular expansion of tho 

 plexus ;#, corpus striatum; pi a mater, the choroid plexus, 

 h > P tic nerve - which enters from the exterior 



at a spot on the mesial side of the vesicle, at its back 



part, where there is a breach of continuity in the brain 



