FORCED MOVEMENTS 605 



" 8. Olivary bodies, restiform bodies (Magendie); 



"9. External part of the anterior pyramids (Magendie); 



" 10. Portion of the bulb from which the facial nerve arises (Brown- 

 Sequard) ; 



"n. Optic nerves; 



"12. Semicircular canals (Flourens); auditory nerve (Brown- 

 Sequard)." 



The movements that follow unilateral injury of the parts mentioned 

 above are of two kinds ; namely, rolling of the entire body on its longi- 

 tudinal axis, and turning, always in one direction, in a small circle, called 

 by the French the movement of manage. A capital point to determine 

 in these phenomena is whether the movements are due to paralysis or 

 enfeeblement of certain muscles upon one side of the body, to a direct or 

 reflex irritation of the parts of the nervous system involved or to both 

 these causes combined. The experiments of Brown-Sequard and others 

 show that the movements may be due to irritation alone, for they occur 

 when parts of the encephalon and the upper portions of the cord are 

 simply pricked, without section of fibres. When there is extensive 

 division of fibres, it is probable that the effects of the enfeeblement of 

 certain muscles are added to the phenomena produced by simple irrita- 

 tion. The most satisfactory explanation of these movements is the one 

 proposed by Brown-Sequard, who attributed them to a more or less con- 

 vulsive action of muscles on one side of the body, produced by irritation 

 of the nerve-centres. He regarded the rolling as simply an exaggera- 

 tion of the turning movements, and places both in the same category. 



It is not necessary to enter into an extended discussion of these 

 experiments. In some of them, the movements have been observed 

 toward the side operated on, and in others, toward the sound side. 

 These differences probably depend on the fact that in certain experi- 

 ments the fibres are involved before their decussation, and in others, 

 after they have crossed in the median line. In some instances the 

 movements may be due to a reflex action, from stimulation of afferent 

 fibres, and in others the action of the irritation may be direct. 



