620 Dynamic Theory. 



citation by stimulating some particular portion of the organ. The lo- 

 calization of the centers of combined movements of the two eyeballs, 

 in particular lobules of the cerebellum in the rabbit, was extremely 

 curious. Thus, when the electrodes were applied to the median lobe at 

 its forward end, the right eye moved outwards and the left inwards, in 

 a horizontal plane. When the center and posterior parts of the middle 

 lobe were irritated, the right eye moved inwards and the left outwards, 

 on the same horizontal plane. Thus it appears that the middle lobe 

 regulates those horizontal movements of the eyes which are harmonious 

 but not symmetrical, and that the upper part of the median lobe and its 

 middle and lower parts, are in functional antagonism. When the elec- 

 trodes were applied to the forward part of the left lateral lobe, the right 

 eye moved downwards and outwards, the left eye upwards and inwards; 

 and when the corresponding point of the right lateral lobe was stimu- 

 lated, the right eye moved upwards and inwards, and the left eye down- 

 wards and outwards, while the conjoint irritation of both lateral points 

 neutralizes both effects. When the middle division of the left lateral 

 lobe was irritated, a downward movement of the right eye, and an up- 

 ward movement of the left eye, were combined with a rotation of each 

 globe on its antero-posterior axis, the left in the direction of the hands 

 of a clock, the right in the contrary direction. But when the irritation 

 was applied to the posterior or lowest division of the left lateral lobe, 

 the two eyes rotated on their antero-posterior axes in the same direction, 

 and contrary to the hands of the clock, so that their vertical meridians 

 retained their parallelism. This last action is what takes place auto- 

 matically when we fix our gaze at any object, and incline our head to 

 the right side, the rotation of the eyeballs in the opposite direction 

 serving to keep the image of the object on tife same spot of the retina, 

 just as do the automatic movements of the eyeballs in the vertical or 

 horizontal plane, when the head is moved upwards or downwards, or 

 from side to side." ( Carpenter.} 



These experiments make it evident that one very important function 

 of the cerebellum is to regulate the movements of the eyes, and to har- 

 monize these movements with the other general muscular motions of the 

 body. Dizziness, resulting from swiftly turning, or from crossing run- 

 ning water, unsteadiness of gait when blindfolded, or in the dark, &c. , 

 are due to a failure of this co-ordinization, or harmonizing. The direc- 

 tion of the vision is changed too rapidly to allow of one adjustment to 

 be completed before another becomes necessary, or the absence of the 

 directing vision leaves the muscular movements without any other guid- 

 ance than they can get from the muscular and auditory senses. 



It is not known with certainty by what nerve connections the eves and 

 the cerebellum are united, but it is thought it is from the pulvinar of 



