ROLLING AND TURNING MOVEMENTS. - 415 



We do not propose to enter into an elaborate discussion of 

 the above experiments, for the reason that they do not seem 

 to have advanced our positive knowledge of the functions of 

 the nerve-centres. In some of them, the movements have 

 been observed toward the side operated upon, and in others, 

 toward the sound side. These differences probably depend 

 upon the fact, that in certain experiments, 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. Judging from the fact that most of the en- 

 cephalic commissural fibres are apparently insensible and 

 inexcitable under direct stimulation, it is probable that the 

 action is generally reflex. 



Though we have avoided a full discussion of the question 

 under consideration, it is one that may be, to some, of con- 

 siderable interest, from the remarkable character of the phe- 

 nomena observed, and the reader is referred for further in- 

 formation to the elaborate chapter on this subject by Yulpian 1 

 and a recent article by Onimus. 2 In the latter article, there 

 are many curious experiments upon frogs and aquatic birds. 



In concluding the physiological history of the encephalon, 

 we have only to refer to the general properties of certain of 

 the peduncles. Longet found that direct irritation of the 

 superior and the inferior peduncles of the cerebellum, in 

 rabbits, produced pain, but the disturbance consequent upon 

 exposure of the parts did not allow of any accurate observa- 

 tions upon the movements. He says nothing of the general 

 properties of the middle peduncles or of the peduncles of the 

 cerebrum. 3 



1 VULPIAN, Systeme nerveux, Paris, 1866, p. 583, et seq. 



9 ONIMUS, Recherches experimentales sur les phenomenes consecutifs d I 'ablation 

 du cerveau et sur les mouvements de rotation. Journal de fanatomie et de la phy- 

 siologic, Paris, 1870-'7l, tome vii., p. 662. 



8 LONGET, Traite de physiologic, Paris, 1869, tome iii., p. 398. 

 127 



