32 CLASSIFICATION 



The brain, although it has the same parts, yet it has them closer 

 connected, and the skull is more in contact with it. 



Of the Fifth Class, or Fowl. — The brain in this class is larger in pro- 

 portion to the size of the animal than in the foregoing. It consists 

 of the pulpy substance, but is not very distinctly of two kinds, cortical 

 and medullary. 



It would seem to be made up of six parts, viz. the two hemispheres 

 of the cerebrum ; the two round bodies, one on each side of the medulla 

 oblongata, pretty much detached, which would seem to answer to the 

 two middle lobes, although their situation with respect to the skull is 

 different, for they are under the lateral processes ; fifth, the cerebel- 

 lum; and sixth, the medulla oblongata, which is the common base. 

 The cerebellum is considerably behind the posterior lobes, and is large 

 in proportion to the size of the whole brain. 



The two hemispheres do not seem to unite, although they are so 

 close to one another as to be hardly separated by means of the inner 

 sides of the two lateral ventricles. The two lateral ventricles are 

 very large, and may be called the broad cavities ; they begin forwards 

 near the anterior points where the olfactory nerves arise, and near that 

 surface where the two hemispheres are in contact with one another ; 

 each ventricle passes backwards, and winds round the posterior end, 

 but does not extend so far to the outer or lateral parts of the hemi- 

 sphere as to come forwards again. The part of the brain which makes 

 the inner and posterior wall of this cavity is very broad, and so thin in 

 many places as to appear like a membrane or pia mater only. On the 

 inner surface it is concave, on the external it is convex, and the oppo- 

 site or inner side of the cavity, which is the major part of the brain, 

 is convex, which answers to the concavity of the outer ; so that the 

 two surfaces are moulded to, and in contact with, one another. When 

 this outer portion is taken off, the brain is nearly of the same shape 

 and size as before. The plexus choroides is a vessel which comes from 

 the lower part of the cavity of the two thalami, or from the upper sur- 

 face of the medulla oblongata, and runs backwards and upwards through 

 the cavity, and spreads into a broad loose flat fringy end. At the 

 lower part of the division of the two hemispheres is the third ventricle, 

 like a groove ; the anterior end terminates in the infundibulum below 

 the optic nerves, but at some distance ; the posterior end is continued 

 into the fourth ventricle in the quadruped, or the sixth ventricle in 

 this class. 



The two lateral bodies 1 which are on the sides of the medulla ob- 



1 [The optic lobes, or bigeminal bodies.] 



