626 CEREBRAL CONVOLUTIONS. [BOOK m. 



FIG. 85. THE AREAS OJP THE CEREBRAL CONVOLUTIONS OF THE DOG, ACCORDING 



TO FERRIER. 



0. The Olfactory Lobe. A. The Fissure of Sylvius. B. The Crucial Sulcus. 



Stimulation by the interrupted current of the areas indicated by the several 

 circles produces the following results. 



(1) The hind leg is advanced as in walking. (3) Lateral or wagging motion of 

 the tail. (4) Eetraction and adduction of the opposite forelimb. (5) Elevation of 

 the shoulder of, and extension forwards of, the opposite forelimb. (7) Closure of 

 the opposite eye caused by combined action of the orbicular and zygomatic muscles. 

 (8) Extraction and elevation of the opposite angle of the mouth. (9) The mouth is 

 opened and the tongue moved, sometimes barking is produced. (11) Extraction of 

 the angle of the mouth. (12) Opening of the eyes and dilation of the pupils; the 

 eyes and then the head turning to the opposite side. (13) The eyeballs move to the 

 opposite side. (14) Pricking or sudden retraction of the opposite ear. (15) Torsion 

 of the nostril on the same side. (16) Elevation of the lip and dilation of the 

 nostril (?). 



of precisely limited areas, the stimulation of each area producing a 

 distinct and limited movement, while stimulation of a large surface 

 produced general convulsions. The movements were so precise that 

 they answered each to the spot stimulated almost as completely as 

 a note answers to a key struck on the piano. A somewhat similar 

 relationship has also been observed between various regions of the 

 cortex and the secretion of saliva, the beat of the heart, the con- 

 dition of the pupil, the action of vaso-motor nerves, and other 

 organic functions. 



These experiments, which have not only been confirmed by 

 many observers, but may, with due care, be successfully repeated 

 by any one, clearly shew, in spite of some discordance among 

 various authors as to the exact position and extent of the several 

 'areas,' that there is a connection between electric stimulation of 

 certain areas of the brain-surface and certain bodily movements. The 

 areas in question have been spoken of by some authors as 'motor 

 centres.' Such a term is however undesirable, since it suggests 

 that the brain-surface in a given area is largely occupied in giving 

 rise to the coordinate nervous impulses which carry out the 

 movement resulting from stimulation of the area; whereas, as 

 we have already seen from the behaviour of an animal deprived of 



