128 PHYSIOLOGICAL SERIES. 



slight concavity in its anterior face where it abuts against 

 the pseudo-occipital lobes of the cerebrum. It is deeply 

 fissured transversely, as in higher Sharks and Mammals. 

 The medulla is short and passes into the cord by a some- 

 what abrupt constriction. O. 0. 1321 s. 



D. 150. A similar specimen seen from the ventral surface. The 

 optic lobes, tracts, and chiasma are well shown, as is aKo 

 the sharp ventral flexure of the medulla. 0. C. 1321 sa. 



D. 151. The brain of an Ostrich (Strut/no camelus] injected. 

 The right lateral ventricle has been exposed by the removal 

 of the lateral wall. It shows clearly the foramen of Monro, 

 with achoroid plexus an offshoot of the vascular epithelial 

 roof of the thalamencephalon projecting through it inlo 

 the ventricle. On the left an opening has been made in 

 the dorsal wall (pallium) of the hemisphere to show the 

 natural position of the plexus. The outer wall of the right 

 optic lobe has been removed by a tangential section to 

 expose its cavity a lateral diverticulum of the aqueduct of 

 Sylvius. The thickness of its walls is somewhat exagge- 

 rated by the direction of the section. The dorsal parts of 

 the cerebellum have also been cut away, showing the 

 transverse folding of the organ, and laying bare the apex of 

 the cerebellar ventricle an offshoot of the fourth ventricle. 

 A black bristle has been inserted into the ruptured end of 

 the left olfactory bulb and others mark the positions of the 

 ehief cranial nerves. A brown bristle is placed in the cavity 

 of the infundibultun. 0. C. 1322. ///////man. 



D. 152. Part of the section of cerebellum removed from] the 

 preceding specimen. 0. C. 1323. ///////man. 



D. 153. The brain of an Ostrich ( Strut h in raniclita) with several 

 of its cavities exposed from the right side. Tin- corpus 

 st rial um \\;\< been entirely removed, showing the extent of 

 the lateral ventricle in a >;i-itt;il plain-, and the foramen of 

 Monro (indicated l.y a Uue rod). The right optic lobe \\-,\< 

 also been mostly cut away, to show the thickness of the mid- 

 l.rain floor and the relatively thin tectum here upon the 



