200 THE GROWTH OF THE BRAIN. 



disturbances in the intelligence, are also accompanied 

 by abnormalities in fissuration. But further than this it 

 is hardly safe to go. On the hemispheres of the human 

 cerebrum a number of statistical studies of fissuration 

 and measurements have been made. These are mainly 

 to be found in the works of Giacomini, Eberstaller, 

 Cunningham, and Mingazzini. 1 As the result of com- 

 paring the hemispheres in the two sexes, or from the 

 two sides of the same brain, there have been noted 

 by various observers a number of peculiarities in 

 fissuration. These features of the cerebral surface have 

 a range and value remotely to be compared with that 

 of the features of the face, but they are even less constant 

 and less easy to interpret. There are no characters by 

 which the sex of a given brain can be recognised with 

 certainty ; nevertheless investigators are generally agreed 

 that the male brain tends to be more extensively 

 fissured. But concerning such matters as the extent 

 of the frontal lobe or the relations of the Sylvian 

 fissure, and the peculiarities of other important fissures, 

 the differences, if general, are too slight to make 

 practicable their presentation here. 



With the folding of the surface and the production of 

 the gyri are connected several growth problems of great 

 interest. Anatomically there are two conditions to be 

 fulfilled in the development of the cerebral hemispheres. 

 In the first place there must be provision for a large 

 number of fully developed cells, and in the second place 

 these cells must become physiologically connected with 

 one another. It is plain that these two processes do 

 not necessarily go hand in hand, and we may have 

 every combination, from a large number of cortical cells 

 adequately associated, to a small number incompletely 

 associated. On the number and development of the 

 1 Mingazzini, // Cervello, &c., Torino, 1895. 



