GANGLION OF THE TUBER ANNULARE. 401 



the tuber annulare, but the impression is not conveyed to 

 the cerebrum, and is not recorded by the memory. 



Taking all the experimental facts into consideration, the 

 following seems to be the most reasonable view with regard 

 to the function of the tuber annulare as a nerve-centre. 



It is an organ capable of originating a stimulus giving 

 rise to voluntary movements, when the cerebrum, corpora 

 striata, and the optic thalami, have been removed, and prob- 

 ably regulates the automatic voluntary movements of station 

 and progression. Many voluntary movements, the result of 

 intellectual effort, are made in obedience to a stimulus trans- 

 mitted from the cerebrum, through conducting fibres in the 

 tuber annulare, to the motor conductors of the cord and the 

 general motor nerves. 



The tuber annulare is also capable of perceiving painful 

 impressions, which, when all of the encephalic ganglia are 

 preserved, are also conducted to and are perceived by the 

 cerebrum, and are remembered ; but there are distinct evi- 

 dences of the perception of pain, even when the cerebrum 

 has been removed. 



Cases of disease or injury of the tuber annulare on one 

 side in the human subject show that its action is crossed. 

 It is a curious fact that lesions of the encephalon involving 

 the pons may be located during life by the existence of what 

 is known as alternate paralysis ; i. e., there is hemiplegia on 

 the side opposite to the brain-lesion, attended with paralysis 

 of the facial on the same side as the lesion, so that the fa- 

 cial palsy and the hemiplegia are on opposite sides of the 

 body. We have already cited, in connection with the physi- 

 ology of the facial nerve, the cases collected by Gubler, of 

 this alternate paralysis, in illustration of the decussation of 

 the deep fibres of origin of the facial ; for when the lesion 

 involves parts of the encephalon anterior to or above the 

 pons, the facial paralysis is on the same side as the hemi- 

 plegia. 1 Additional cases of alternate paralysis have been 



1 See page 147. 



