530 THE NERVOUS SYSTEM. 



been observed, no other office is manifest in it than that 

 of regulating and combining muscular movements, or of 

 enabling them to be regulated and combined by so inform- 

 ing the mind of the state and position of the muscles that 

 the will may be definitely and aptly directed to them. 



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 

 from the medulla oblongata and spinal cord the influence 

 of one of the hemispheres of the cerebellum, strangely 

 disordered movements ensue. The animals fall down on 

 the side opposite to that on which the crus cerebelli has 

 been divided, and then roll over continuously and re- 

 peatedly ; the rotation being always round the long axis 

 of their bodies, and from the side on which the injury has 

 been inflicted.* The rotations sometimes take place with 

 much rapidity ; as often, according to M. Magendie, as 

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

 Similar movements have been observed in men ; as by M. 

 Serres in a man in whom there was apoplectic effusion in 

 the right crus cerebelli; and by M. Belhomme in a woman, 

 in whom an exostosis pressed on the left crus.f They 



* Magendie and Miiller, and others following him, say the rotation 

 is towards the injured side ; but Longet and others more correctly give 

 the statement as in the text. The difference has probably arisen from 

 using the words right and left, without saying whose right and left are 

 meant, whether those of the observer or those of the observed. "When, 

 for example, an animal's right crus cerebelli is divided, he rolls from his 

 own right to his own left, but from the left to the right of one who is 

 standing in front of him. 



f See such cases collected and recorded by Dr. Paget in the Ed. Med. 

 and Surg. Journal for 1847. 



