THE NERVOUS SYSTEM. 131 



ever, which can be drawn from this, is, that the integrity of this par- 

 ticular convolution i-s essential to the faculty of speech; we cannot con- 

 clude that it is necessarily the centre for language. It may be only one 

 link in the complete chain of nervous connections necessary for the trans- 

 lation of an idea into articulate expression. 



It seems highly probable that the corresponding right convolutions 

 can take on the same functions as the left; and it is in this way that we 

 can explain those cases in which recovery of speech takes place, though 

 the left frontal convolution still remains diseased. 



PINEAL AND PITUITARY BODIES. 



Nothing is known of the* function of the pineal and pituitary bodies. 

 They have been, indeed, supposed by some to be rather ductless glands 

 than nervous organs (p. 10, Vol. II.). 



Experimental Localizations. Attempts have been made to localize 

 cerebral functions by means of experiments on the lower animals. It had 

 long been well known that the cerebral hemispheres could not be excited 

 by mechanical, chemical, or thermal stimuli, but Fritsch and Hitzig 

 were the first to show that they are amenable to electric irritation. They 

 employed a weak constant current in their experiments, applying a pair 

 of fine electrodes not more than -fa in. apart to different parts of the 

 cerebral cortex. The results thus obtained have been confirmed and 

 extended by Ferrier. 



The following are the fundamental phenomena observed in all these 

 cases: 



(1.) Excitation of the same spot is always followed by the same move- 

 ment in the same animal. (2.) The area of excitability for any given 

 movement is extremely small, and admits of very accurate definition. 

 (3.) In different animals excitations of anatomically corresponding spots 

 produce similar or corresponding results (Burdon-Sanderson). 



The various definite movements resulting from the electric stimulation 

 of circumscribed areas of the cerebral cortex, are enumerated in the 

 description of the accompanying figures of the dog and monkey's brain. 



In the case of the dog, the results obtained are summed up as follows, 

 by Hitzig. 



(a. ) One portion (anterior) of the convexity of the cerebrum is motor; 

 another portion (posterior) is non motor, (b.) Electric stimulation of the 

 motor portion produces co-ordinated muscular contraction on the opposite 

 side of the body. (c. ) With very weak currents, the contractions pro- 

 duced are distinctly limited to particular groups of muscles; with 

 stronger currents the stimulus is communicated to other muscles of the 



