CHAP. IX.] AND OF BIRDS. 138 



* sylvian ') always recognizable in the brain of higher 

 Mammals. The cavity within each of the cerebral lobes 

 answering to the ' lateral ventricles ' of the human brain* 

 is comparatively large, and projecting from the anterior 

 and external part of the floor of each of them, there is 

 an eminence generally admitted to correspond to the 

 1 Corpus Striatum ' in the brain of Man and Mammals 

 generally. The inner walls of the lateral ventricles are 

 thin, and almost in contact with one another. They con- 

 stitute the inner boundaries of the cerebral lobes. 



FIG. 66. 



FIG. 65. Brain of Common Fowl in adult condition. (Spurzheim.) c, Optic lobes 

 in part hidden by (6) cerebral hemispheres. 



FIG. 66. Brain of Pigeon, side view. (Mivrart.) 1, Olfactory lobe; 2, cerebral 

 hemisphere ; 3, pineal body ; 4, optic lobe ; 5, cerebellum ; 6, pituitary body ; 8, optic 

 nerve. 



These lobes are structurally connected, as in Reptiles 

 and Fishes, by a well-marked ' anterior commissure,' 

 while above and behind it there exists another set of con- 

 necting fibres, deemed by some anatomists to represent 

 the commencement of the ' Corpus Callosum.' This latter 

 is the great transverse commissure which unites the two 

 halves of the brain, and whose size increases as we pass 

 from lower to higher orders of the Mammalian series. 



* These are the first and second ventricles. The third is 

 situated between the cerebral peduncles, the fourth at the back 

 of the medulla, and the fifth ventricle will be subsequently re- 

 lerred to in the description of the brain of Quadrupeds. 



