CHAP. XI,] FUNCTIONS OF THE ENCEPHALON. 343 



vulsive movements in muscular parts which receive nerves from it, 

 and, through the spinal cord,, in the muscles of the trunk. Spasm 

 of the glottis, difficulty of deglutitition, irregular acts of breathing, 

 result from irritation of the medulla oblongata : and, if the excite- 

 ment be propagated to the cord, convulsions will become more or 

 less general. 



If a lesion affect one half of the medulla oblongata, does it pro- 

 duce convulsions or paralysis on the opposite side of the body? 

 This question may certainly be answered in the affirmative, when 

 the seat of the lesion is in the continuations of the columns of the 

 medulla oblongata above the posterior margin of the pons. It 

 is not so easily solved, however, when the disease is situate 

 below the pons. The results of experiment on this subject 

 are contradictory, owing probably to the extreme difficulty of 

 limiting the injury inflicted to a portion of the medulla on one 

 side ; and those of Flourens are of no value for the decision of 

 this question, as it appears that he injured chiefly the restiform 

 bodies. Anatomy suggests, that a lesion limited to either anterior 

 pyramid would affect the opposite side of the trunk ; for it is known 

 that such an effect follows disease of the continuation of it in the 

 mesocephale or cms cerebri ; and that lesion limited to the posterior 

 half of the medulla on either side would affect the same side of the 

 body, no decussation existing between the fibres of opposite resti- 

 form or posterior pyramidal bodies. The irritating or depressing 

 influence of the lesion would probably be extended to the spinal 

 gray matter of the same side. 



That the medulla oblongata is the channel through which the 

 operations of the brain are associated in voluntary actions with the 

 spinal cord, is shown by the fact that paralysis of all the muscles of 

 the trunk follows the separation of the latter organ from the former. 

 It seems not improbable, that the centre of volition is connected with 

 one or both of the glangliform bodies (corpora striata and optic tha- 

 lami) in which the columns of the medulla oblongata terminate 

 above. When the cerebral hemispheres have been removed, as in 

 Flourens' and in Majendie's experiments, the bird is thrown into 

 a deep sleep, a state of stupefaction, and insensibility to surrounding 

 objects. But he can maintain his attitude stand walk, when 

 first propelled fly, if thrown into the air. This continuance of the 

 locomotive power implies some degree at least of mental or volitional 

 effort. All the animal's movements have much of the appearance 

 of the exercise of will, although, doubtless, many of them are in 

 a great degree excited by physical stimuli. Hence there seems 



