GENERAL PHYSIOLOGY OF THE CEREBRUM. 



181 



animals he found that successive ablations of parts of the cerebrum 

 from before backward or from side to side was not followed by 

 a corresponding series of defects in the animals' psychical life. On 

 the contrary, when the quantity of brain substance removed was 

 sufficiently large all these qualities went at once. The choice of 

 animals for these experiments was an unfortunate one, but the 

 results were corroborated in part by a number of instances in 

 which human beings by acci- 

 dent or wounds in battle had 

 lost a part of the brain with- 

 out any apparent defect in 

 their mental powers. There- 

 fore toward the middle of the 

 nineteenth century the preva- 

 lent view in physiology was 

 that the cerebrum is function- 

 ally equivalent in all of its 

 parts. One fact was known 

 in medicine at that time which 

 distinctly contradicted this be- 

 lief , namely, that an injury 

 to the posterior portion of the 

 third frontal convolution in 

 man, on the left side, causes a 

 loss of articulate speech (motor 

 aphasia). But this fact, so sig- 

 nificant to us now, was not 

 properly valued at the time. 

 The beginning of our modern 

 views of cerebral localization 

 is found in the work of Fritsch 

 and Hitzig* (1870), in which 

 they exposed and stimulated 

 electrically the cortex cerebri in 

 dogs. They found that stimu- 

 lation of certain definite areas, 

 particularly in the sigmoid 



gyrus, gave distinct and constant movements in the limbs, face, etc. 

 (see Fig. 81). This work was followed quickly by experiments of a 

 similar kind made by numerous observers, in which the cerebrum was 

 stimulated in various animals and finally in man. In addition, the 

 method of ablation of these areas was employed with subsequent 

 study of the animal in regard to the motor or sensory defects result- 



* Fritsch and Hitzig, "Archiv f. Anatomie und Physiologie und wissen- 

 schaftliche Medizin," 1870, 300. 



Fig. 81. To show the motor areas in the 

 dog's brain as originally determined by 

 Fritsch and Hitzig: s, Sigmoid gyrus; A, center 

 for the neck muscles; -f , center for the ex- 

 tensors and adductors of the forelimb; +, 

 center for the flexors and rotation of fore- 

 limb; #, center for the hind limb; O O, 

 center for the muscles innervated by the 

 facial. 



