FACIAL NERVE. 14:7 



and rabbits, a longitudinal section in the middle line of the 

 ventricle, which would necessarily have divided the fibres 

 passing from one side to the other, without producing nota- 

 ble paralysis of the facial nerves upon either side. 1 This 

 single fact is sufficient to show that the main decussation of 

 the fibres animating the muscles of the face takes place, if 

 at all, at some other point. 



The following curious phenomenon, however, resulting 

 from this section, was noted by Yulpian : He found that 

 although there was no apparent paralysis of the orbicularis 

 muscle of the eye upon either side, the synchronism of the 

 movements of the two muscles seemed to be destroyed. It 

 is well known that in man, and in many of the lower ani- 

 mals, there is an involuntary action of these muscles simul- 

 taneously on the two sides in winking. After a longitudinal 

 section in the median line of the floor of the fourth ventri- 

 cle, the animals winked with either eye alternately, or with 

 one eye for a time without closing the other, but there was 

 no simultaneous action of the muscles on the two sides. 2 



The pathological facts bearing upon the question of de- 

 cussation of the filaments of origin of the facial have long 

 been recognized. They are, in brief, as follows : When 

 there is a lesion of the brain-substance anterior to the pons 

 Yarolii, the phenomena due to paralysis of the facial are 

 observed on the same side as the hemiplegia, opposite to the 

 side of injury to the brain. "When the lesion is either in the 

 pons or below it, the face is affected on the same side, and 

 not on the side of the hemiplegia. In view of these facts, 

 the remarkable phenomenon of hemiplegia upon one side 

 and facial paralysis upon the other is regarded as indi- 

 cating, with tolerable certainty, that the injury to the brain 

 has occurred upon the same side as the facial paralysis, 

 either in or posterior to the pons Yarolii. It is unnecessary 



1 VULPIAK, Lemons sur la phy&iologie generate et comparee du systeme nervevx, 

 Paris, 1866, p. 480. 



2 VCLPIAX, op. cit., p. 481. 



