700 THE CEREBRUM 



Whichever view is accepted, it must be evident that these different 

 association regions are used for purposes of synthetizing the sensory 

 impressions into perceptions and concepts. In accordance with Flech- 

 sig, it may thus be held that the association areas are the places in 

 which sense impressions are built up into organized knowledge, and 

 where a complex mental image is formed of conditions in our internal 

 and external world. Typical association regions are, of course, the 

 parieto-occipital and frontal realms. Regarding the latter, little prog- 

 ress has been made. It has been stated by Bolton 1 that mentally defi- 

 cient persons (amentia) exhibit a thinning of the cortex which is especially 

 marked in the frontal region. These atrophic changes are also appar- 

 ent in idiotic and demented persons; in fact, it is claimed that they 

 bear a direct relationship to the degree of the idiocy. Moebius 2 

 calls attention to the fact that the laterobasal portions of the frontal 

 lobes are strongly developed in mathematicians. Thus, the brain of 

 Helmholtz showed a uniform massiveness, but especially in the region 

 between the gyrus angularis and the gyrus temporalis superior. 3 

 According to Guzmann, 4 the gyrus angularis is very prominent in 

 people who possess a special talent for music. Mills 5 argues that the 

 intellectual states are controlled by the frontal lobes, while Spitzka's 6 

 observations rather tend to prove a predominance of the posterior 

 association fields in intellectual men. 



Cases of extensive destruction of the frontal lobes have been cited 

 repeatedly. Most commonly, however, reference is made to that of a 

 workman whose frontal lobes were extensively lacerated by the end of a 

 crowbar, driven through his skull by a premature explosion of dynamite 

 (1850). In all these instances a decided change in the character and 

 intelligence of the individual was noted. The more recent observa- 

 tions of Phelps, 7 Miiller 8 and Schuster, 9 however, have shown that a 

 deterioration or loss of the higher mental qualities does not always 

 follow, although minor mental changes, such as weakness of the memory, 

 insane desires, and depression, are usually present. In all those cases 

 in which these symptoms were the result of circumscribed tumors 

 (glioma), the removal of the growth was generally followed by a com- 

 plete mental recovery. In this connection, mention should also be 

 made of the experiments of Franz 10 which have proved that the removal 

 of the frontal lobes in cats and monkeys leads to the loss of habits 

 previously formed by brief periods of training. The habits so lost, 



1 Brain, 1903, 215, and 1910, 26. 



2 Uber die Anlage der Mathematik, Leipzig, 1900. 



8 Hansemann, Zeitschr. fur Psych, der Sinnesorgane, xx, 1899, 1. 

 4 Anat. Anzeiger, xix, 239. 



6 Univ. of Pennsylvania Med. Bull., xvii, 1904, 90. 

 Med. Record, 1901, and N. Y. Med. Jour., 1901. 



7 New York Med. Jour., Ixi, 1895, 8. 



8 Allg. Zeitschr. fur Psychiatric, lix, 1902, 830. 



9 Psych. Storungen bei Hirntumoren, 1902. 

 10 Archives of Psychology, March, 1907. 



