

THE NERVOUS SYSTEM. 119 



inferred that the cerebellum belongs neither to the sensory nor the intel- 

 lectual 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 Flour ens; and, on the whole, it gains sup- 

 port 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. 



Foville supposed that the cerebellum is the organ of muscular 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 explained on this hypothesis as on that of the cerebellum 

 being the organ for combining movements. A harmonious combination 

 of muscular actions must depend as much on the capability of appreciating 

 the condition of the muscles with regard to their tension, and to the 

 force with which they are contracting, 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 the seat of mus- 

 cular sense, or to the centre for combining muscular actions, that experi- 

 ments on the subject afford no proof in one direction more than the other. 



The theory once believed, that the cerebellum is the organ of sexual 

 passion, has been long disproved. 



Forced Movements. The influence of each half of the cerebellum 

 is directed to muscles on the opposite side of the body; and it would appear 

 that for the right ordering of movements, the actions of its two halves 

 must be always mutually balanced and adjusted. For if one of its crura, 

 or if the pons on either side of the middle line, be divided, so as to cut off 

 the medulla oblongata and spinal cord the influence of one of the hemi- 

 spheres of the cerebellum, strangely disordered movements ensue (forced 

 movements). The animals fall down on the side opposite to that on which 

 the crus cerebelli has been divided, and then roll over continuously and 

 repeatedly; the rotation being always round the long axis of their bodies, 

 and generally from the side on which the injury has been inflicted. The 

 rotations sometimes take place with much rapidity; as often, according to 

 Magendie, as sixty times in a minute, and may last for several days. 

 Similar movements have been observed in men; as by Serres in a man in 

 whom there was apoplectic effusion in the right crus cerebelli; and by 

 Belhomme in a woman in whom an exostosis pressed on the left crus. 

 They may, perhaps, be explained by assuming that the division or injury 

 of the crus cerebelli produces paralysis or imperfect and disorderly move- 



