82 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



4- Relative Size of Frontal Lobe.— The highest 

 functions of the intellect are connected with the frontal 

 lobe of the cerebrum. This is marked off by the fis- 

 sure of Rolando. In man the portion anterior to this 

 fissure is large. In monkeys the fissure is plain, but 



Man 



Fig. 54. — Diagram showing all the stages in one. 



the anterior lobe is much smaller, and increasingly so 

 as we go down the scale of monkeys. The fissure is 

 not certainly discernible at all below monkeys. 



CEPHALIZATION. 



This may be defined as headward development. Intro- 

 duced by Dana to. express the gradual transfer of func- 

 tions headward by the modification of homologous organs 

 as we go up the scale of Crustacea (see page 268), .we 

 here use it in a similar but a wider sense as the gradual 

 increasing dominance of higher over lower functions in 



