1864.] 



Prof. Sylvester on Newton^s Rule, ^c. 



179 



The voluntary muscles are under a double influence — from the cerebrum 

 and from the cerebellum. The anterior Hmbs are chiefly under the influ- 

 ence of the cerebrum ; the posterior, of the cerebellum. Cerebellar move- 

 ments are apt to be habitual, while cerebral are impulsive. The cerebellum 

 acts when the cerebrum is removed, though when both organs exist it is 

 under its control. 



Part II. 



From an analysis of one case of congenital absence of the cerebellum, one 

 of disease of the whole organ, and 46 of disease of a portion of it, the fol- 

 lowing deductions are stated : — 



The only faculty which constantly suffers in consequence of changes in 

 the cerebellum, is the power of voluntary movement. 



When the organ is absent or defective congenitally, we have want of 

 action in the muscles of the lower extremities. 



When the entire structure is changed by disease, we have loss of volun- 

 tary power, either general throughout the trunk, or limited to the lower 

 limbs — which results are about equally frequent. 



From the manner in which the paralysis was distributed in cases of disease 

 of a part of the organ, it is inferred that each lobe is in connexion as a source 

 of voluntary movement with all the four limbs, but in the greatest degree 

 with the limbs of the opposite side, and with the lower more than with the 

 upper extremities. 



The occasional occurrence of loss of visual power, and alterations of the 

 sexual propensity, is referred to the conveyance of irritation to the corpora 

 quadrigemina in one case, and the spinal cord in the other. 



From both sources of knowledge it is concluded that the cerebellum has 

 distinct offices. 



It is a source of voluntary motor power to the muscles supplied by the 

 spinal nerves. It influences the lower more than the upper limbs, and pro- 

 duces habitual rather than impulsive movements . Each lobe affects both 

 sides of the body, but most that opposite to itself. 



Secondly, the cerebellum has a power which has been described as 

 that of " coordination," which is similarly distributed. 



Finally, it is suggested that the outer portion of the organ may be the 

 source of its voluntary motor power, while its inner layer is the means of 

 regulating its distribution. 



II. "An Inquiry into Newton^s Rule for the Discovery of Ima- 

 ginary Roots.^' By J. J. Sylvester, F.R.S., Correspondent of 

 the Institute of France. Received April 6, 1864. 



(Abstract.) 



In the * Arithmetica Universalis,' in the ^chapter " De Resolutione Equa- 

 tionum," Newton has laid down a rule, admirable for its simplicity and 

 generality, for the discovery of imaginary roots in algebraical equations, and 



p 2 



