632 



PHYSIOLOGY OF THE CEREBRUM 



of various kinds which both served to establish the doctrine of different physio- 

 logical functions for different cortical regions, and at the same time to greatly 

 broaden and deepen our knowledge of the cerebral functions. 



Since very little is known with regard to the physiological purposes of the 

 basal ganglion (e. g., the nucleus candatus, nucleus lentiformis, the gray masses 

 of the claustrum, etc.) belonging properly to the cerebrum, we shall pass over 

 them here and in this chapter shall consider first the motor and sensory areas of 

 the cortex, and then take up the psycho-physical functions of the cerebrum. 



FIRST SECTION 

 THE MOTOR AND SENSORY AREAS OF THE CORTEX 



Scr 



Scr. 



PSG 



COR 



1. THE MOTOR AREAS 



A. GENERAL SURVEY 



The results of Fritsch and Hitzig to which we have referred on the pre- 

 ceding page were as follows : No movements were obtained by stimulation 



of the posterior part of the cere- 

 bral cortex with weak electric cur- 

 rents. But when the current was 

 applied to the anterior part, move- 

 ments appeared on the opposite side 

 of the body. With a weak stimulus 

 the effect was confined to certain 

 sharply defined groups of muscles. 

 With a stronger stimulus the move- 

 ments appeared also in other groups 

 on the same side (cf. Fig. 282). 



With rapidly repeated induction 

 shocks applied to the different 

 points, the appropriate muscles 

 could be thrown into tetanus. Con- 

 tinued for several seconds, this form 

 of stimulus produced a persistent 

 tetanus which might spread to all 

 parts of the body (cortical epilepsy, 

 cf. below, page 641). 



The first question suggested by 

 these observations is, what part of 

 the cerebrum is the part primarily 

 stimulated by the current the cor- 

 tex, the underlying white matter, or 

 the deeper parts of the brain? 



The answer is unanimous, that the cortex represents the immediate point 

 of attack. The following are among the most important experimental proofs 

 of this proposition: 



FIG. 282. Dorsal surface of the dog's brain, 

 with the excitation points indicated according 

 to Fritsch and Hitzig. A, neck muscles; -f, 

 extensors and adductors of the foreleg; +, 

 flexion and rotation of the foreleg; #, hindleg; 

 O, face; Scr, sulcus cruciatus; ASG, anterior 

 sigmoid gyrus; PSG, posterior sigmoid gyrus; 

 COR, coronary gyrus; cor, coronary fissure; 

 /, //, 777, IV, first to fourth external con- 

 volutions. 



