198 FUNCTIONS OF THE NERVOUS SYSTEM. 



do, Flourens, Magendie, and Hertwig. 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 

 movements 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 combined 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, however, 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 mus- 

 cles ; 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 Hert- 

 wig. 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. 



269. All these results are objected to by those who assert that the Cere- 

 bellum is the seat of the sexual instinct ; on the ground that the observed 

 aberrations of the motor functions are sufficiently accounted for, by the gene- 

 ral 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- 

 taining the equilibrium, being remarkably preserved after the loss of them. 



270. Upon comparing these results with the preceding table, a remarkable 

 correspondence will be observed between them. The classes which have the 

 greatest variety of movements, and which require for them the most perfect 

 combination of a large number of separate muscular actions, have, taken col- 

 lectively, the largest Cerebellum. Of all classes of Vertebrata, Reptiles are 

 the most inert ; and their motions require the least co-ordination. The active 

 predaceous Fishes far surpass them in this respect; and may be compared 

 with Birds, in the energy of their passage through the water, and in their 

 facility of changing their direction during the most rapid progression. The 

 Cerebellum, accordingly, bears to the Spinal Cord in them, very much the 

 same 'proportion as it does in Birds. On the other hand, the Flat Fish, which 

 lie near the bottom of the ocean, and which have a much less variety of 

 movement, have a very much smaller cerebellum: and the Vermiform Fishes, 

 which are almost or completely destitute of fins, and whose progression is 

 accomplished by flexion of the body, have a Cerebellum so small as to be 



