THE BRA IX. 439 



of the cerebellum, more or less extensive, have existed without recorded 

 disturbances of muscular coordination. A large majority of these 

 patients were confined to a sick-room, and many of them to the bed ; 

 consequently there could be no opportunity of observing a want of 

 natural coordination in the more complicated movements, if any such 

 existed. A patient, suffering from the gradual diminution of a nervous 

 function, accommodates himself to it by abstaining from the attempt 

 to do what he knows is impossible, and endeavors to accomplish his 

 objects by other means. Moreover, in many cases of disease of the 

 cerebellum, symptoms of want of coordinating power have been dis- 

 tinctly recorded. 



The data derived from comparative anatomy show a general corre- 

 spondence in the development of the cerebellum and the variety of 

 muscular action. In fish, as a rule, it is of good size compared with 

 other parts of the brain ; and although direct progression in this class 

 is accomplished by a comparatively simple mechanism, namely, the 

 lateral flexion and extension of the spinal column with its expanded 

 fins and tail, yet their movements through the water or in leaping 

 out of it, while pursuing and taking their prey, are rapid and vigorous, 

 and are promptly varied in any direction. In the frog, on the other 

 hand, the movements of progression consist of little else than straight- 

 forward flexion and extension of the posterior limbs ; and the cerebel- 

 lum is much inferior in size to that of fishes, forming only a thin 

 narrow ribbon of nervous matter across the upper part of the fourth 

 ventricle. In turtles, locomotion is accomplished by consentaneous 

 action of the anterior and posterior limbs, while the cerebellum exhibits 

 a corresponding increase of development. In the alligator, whose mo- 

 tions approximate still more closely to those of the quadrupeds, the 

 cerebellum is also larger in proportion to the remaining parts of the 

 brain. In birds, in quadrupeds, and in man there is a very evident 

 increase in the size and convolutions of the cerebellum, corresponding 

 with the greater variety and delicacy of their movements. These facts 

 are not decisive in determining the physiological function of this por- 

 tion of the brain ; but they show that the assumption of a coordinating 

 power in the cerebellum is not at variance with its comparative anatomy. 



All that we know with certainty, therefore, in regard to the cerebel- 

 lum, indicates its close connection with the power of coordination. By 

 its inferior peduncles it is in communication with the posterior columns 

 of the spinal cord, and by its superior peduncles with the upper portion 

 of the crura cerebri ; and, so far as its function can be demonstrated 

 from experiment, it appears to act as a general centre of combination 

 for voluntary movement. 



The Medulla Oblongata, 



The medulla oblongata is distinguished from the spinal cord, of which 

 it forms the direct continuation, by its expanded form, the different 



