416 . THE NERVOUS SYSTEM. 



(whose experiments have been abundantly confirmed by those 

 of Bouillaud, Longet, and others) extirpated the cerebellum 

 in birds by successive layers. Feebleness and want of har- 

 mony of the movements were the consequence of removing the 

 superficial layers. When he reached the middle layers, the 

 animals became restless without being convulsed ; their move- 

 ments were violent and irregular, but their sight and hearing 

 were perfect. 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 equi- 

 librium. When an animal in this state was laid upon its 

 back, it could not recover its former posture ; but it fluttered 

 its wings, and did not lie in a state of stupor ; it saw the blow 

 that threatened it, and endeavored to avoid it. Volition, sen- 

 sation, and memory, therefore, were not lost, but merely the 

 faculty of combining the actions of the muscles ; and the en- 

 deavors of the animal to rnaintan its balance were like those 

 of a drunken man. 



The experiments afforded the same results when repeated 

 on all classes of animals ; and, from them and the others be- 

 fore referred to, Flourens inferred that the cerebellum belongs 

 neither to the sensitive nor the intellectual apparatus; and 

 that it is not the source of voluntary movements, although it 

 belongs to the motor-apparatus ; but is the organ for the co- 

 ordination of the voluntary movements, or for the excitement 

 of the combined action of muscles. 



Such evidence as can be obtained from cases of disease of 

 this organ confirms the view taken by Flourens ; and, on the 

 whole, it gains support from comparative anatomy ; animals 

 whose natural movements require most frequent and exact 

 combinations of muscular actions being those whose cerebella 

 are most developed in proportion to the spinal cord. 



M. Foville holds that the cerebellum is the organ of muscu- 

 lar sense, i. e., the organ by which the mind acquires that 

 knowledge of the actual state and position of the muscles which 

 is essential to the exercise of the will upon them ; and it must 

 be admitted that all the facts just referred to are as well ex- 

 plained on this hypothesis as on that of the cerebellum being 

 the organ for combining movements. A harmonious combina- 

 tion of muscular actions must depend as much on the capa- 

 bility of appreciating the condition of the muscles with regard 

 to their tension, and to the force with which they are con- 

 tracting, as on the power which any special nerve-centre may 

 possess of exciting them to contraction. And it is because 

 the power of such harmonious movement would be equally 

 lost, whether the injury to the cerebellum involved injury to 



