FUNCTIONS OF THE CEREBELLUM. 351 



species which approach most nearly to the Mammalia in general conformation, 

 such as the Ostrich ; but in those of most active and varied powers of flight. 

 Lastly, on ascending the scale of Mammiferous animals, we cannot but be 

 struck with the rapid advance in the proportional size of the Cerebellum, that 

 we observe, as we rise from the lowest, which are surpassed in this respect 

 by many Birds, towards Man, in whom it attains a development which appears 

 enormous, even when contrasted with that of the Quadrumana. 



459. We have next to inquire what evidence can be drawn from Experi- 

 mental investigations on the same subject: and in reference to this it is desirable 

 to remark, in the first place, that the experimental mode of inquiry is perhaps 

 more applicable to this organ than to other parts of the Encephalon; inasmuch 

 as it can be altogether removed, with little disturbance of the actions imme- 

 diately essential to life; and the animals soon recover from the shock of the 

 operation, and seem but little affected, except in some easily-recognized par- 

 ticulars. The principal experimenters upon this subject have been Rolando, 

 Flourens, Magendie, Hertvvig, and Longet. It is not to be expected, that there 

 should be an exact conformity among the results obtained by all. Every one 

 who has been engaged in physiological experiments, is aware of the amount 

 of difference caused by very minute variations in their circumstances; in no 

 department of inquiry is this more the case than in regard to the Nervous 

 System ; and such differences are yet more likely to occur, in experiments 

 made upon the Nervous Centres, than in those which concern their trunks. 

 The investigations of Flourens are the most clear and decisive in their results ; 

 and of these we shall accordingly take a general survey. He found that, when 

 the Cerebellum was mechanically injured, the animals gave no signs of sensi- 

 bility, nor were they affected with convulsions. When the Cerebellum was 

 being removed by successive slices, the animals became restless, and their move- 

 ments were irregular; and by the time that the last portion of the organ was cut 

 away, the animals had entirely lost the powers of springing, flying, walking, 

 standing, and preserving their equilibrium, in short, of performing any com- 

 bined muscular movements, which are not of a simply-reflex character. When 

 an animal in this state was laid upon the back, it could not recover its former 

 posture; but it fluttered its wings and did not lie in a state of stupor. When 

 placed in the erect position, it staggered and fell like a drunken man, not, how- 

 ever, without making efforts to maintain its balance. When threatened with a 

 blow, it evidently saw it, and endeavoured to avoid it. It did not seem that the 

 animal had in any degree lost voluntary power over its several muscles ; nor did 

 sensation appear to be impaired. The faculty of combining the actions of the 

 muscles in groups, however, was completely destroyed ; except so far as those 

 actions (as that of respiration) were dependent only upon the Reflex function 

 of the Spinal Cord. The experiments afforded the same results, when made 

 upon each class of Vertebrated animals; and they have since been repeated, 

 with corresponding effects, by Bouillaud and Hertwig. The latter agrees with 

 Flourens, also, in stating that the removal of one side of the Cerebellum affects 

 the movements of the opposite side of the body; and he further mentions 

 that, if the mutilation of the Cerebellum have been partial only, its function is 

 in great degree restored. 



460. All these results are objected to by those who assert that the Cerebel- 

 lum is the seat of the sexual instinct; on the ground that the observed aberra- 

 tions of the motor functions are sufficiently accounted for, by the general 

 disturbance which an operation so severe must necessarily induce. The 

 fallacy of this objection, however, is shown by the fact, that the much more 

 severe operation of removing the Hemispheres does not occasion such an 

 aberration ; the power of performing the associated movements, and of main- 



