PHYSIOLOGY OF THE CEREBRUM 631 



that the cerebral hemispheres have not one and the same function in all of their 

 parts; it has shown that in the production and elaboration of the different kinds 

 of sensations as well as in the influence of the cerebrum on the functions of the 

 body, entirely different areas of the hemispheres are active. 



We may go farther and say that we have certain grounds for believing that 

 different sections of the cerebrum participate in the different mental processes; 

 yet the modern doctrine of cerebral localization is at bottom something quite 

 different from the old phrenology. Phrenology assumed that there were a num- 

 ber of different organs in the brain, each specifically set aside for some complex 

 function, although that function was sometimes purely metaphysical. The new 

 doctrine has been content to establish first of all the importance of the different 

 parts of the brain for the functions of the body and for the sensations produced 

 by stimulation of the afferent nerves. It has, it is true, ventured a step farther 

 and has sought to bring the activity of the mind under physiological investiga- 

 tion. But these investigations aim to discover how the psychical functions can 

 be carried out by the cooperation of the various parts of the brain exactly the 

 reverse process, therefore, of the phrenology of Gall. Finally, the spirit of mod- 

 ern research is poles asunder from the spirit of phrenology: it will not forcibly 

 warp the facts into line with preconceived ideas and arbitrary hypotheses ; but 

 it seeks to be entirely free from bias, and in this spirit to determine by observa- 

 tion and experiment the facts which may be able to help us on toward a deeper 

 theoretical comprehension of the cerebral functions. 



As early as 1825, Bouillaud tried to show that lesions of the cerebral hemi- 

 spheres involved loss of the coordinated movements necessary for speech only 

 when the most anterior divisions of the brain, the frontal lobes, were affected. 

 Somewhat later (1836) Marc Dax stated that articulate speech was controlled 

 by a place in the left half of the brain. But his ideas received no encourage- 

 ment in fact they were described as pseudo-scientific. In 1861, however, Broca 

 made definite observations on some diseased cases and was able to establish the 

 fact that (in right-handed persons) destruction of the third frontal convolution 

 of the left hemisphere abolishes the power of speech. 



These statements were soon corroborated by observations on similar cases by 

 other authors, and thus, contrary to Flourens' doctrine, a functional differentia- 

 tion of the cortex into different regions was demonstrated. But there was con- 

 siderable hesitation about giving up the doctrine of the unity of the brain, and 

 it was not until investigations had been carried much further that it was finally 

 overthrown. 



On purely anatomical grounds Meynert concluded that the anterior part of 

 the cerebral hemispheres was more closely related to motion and the posterior 

 part to sensation. Then came (1870) the work of Fritsch and Hitzig by which 

 it was established for all time that different parts of the hemispheres actually 

 have different functions. 



Among the many articles of faith which had long been held with regard to 

 the brain, was the belief that the cerebral cortex was nonexcitable electrically 

 i. e., that no visible effect could be produced by application of the electric current 

 to the cortex. Fritsch and Hitzig showed that this idea was wholly erroneous 

 and demonstrated that by electrical stimulation of the cortex muscular move- 

 ments could be obtained ; but that they could only be obtained when the current 

 was applied to certain definite portions. The resulting movements appeared in 

 various groups of muscles those of the face, the fore or the hind leg, etc. ac- 

 cording to the exact point, within the general area, which was stimulated. From 

 other portions of the cortex the current produced no visible effect. 



These discoveries excited the greatest interest and led to many new researches 



