374 TRACING OF IMPULSES. 



crescent of the same, and continue through the anterior root-fibers 

 to their destination. On the other hand, the impulses, leaving 

 formatio reticularis in mid-brain, pons or medulla, may enter 

 the nuclei of motor cerebral nerves and be conducted by them to 

 the muscles and glands supplied by cerebral nerves. (2) The 

 impulses may leave the formatio reticularis in the pons, and run 

 to the cerebellar cortex through the brachium pontis. From the 

 cerebellum they may follow the ordinary course through the an- 

 terior descending cerebello-spinal tract, by way of the nucleus 

 of Deiters, to the anterior gray columna of the cord. (3) Impul- 

 ses having arrived at the cerebellar cortex by way of the brachia 

 conjunctiva and brachia pontis, may descend through the cere- 

 bello-olivary tract, in the restiform body, to the opposite inferior 

 olive, and be carried on through descending axones of the olive, 

 in the lateral column, to the gray matter of the cord (Kolliker). 

 (4) Impulses descend from the nucleus of the third cerebral nerve 

 by way of certain fibers in the medial longitudinal bundle to the 

 seventh nerve, where it enters into the colliculus facialis, and 

 through the facial nerve innervate the following muscles the 

 frontalis, procerus, corrugator and orbicularis oculi. Hence these 

 muscles are not paralyzed in nuclear facial paralysis. But if the 

 lesion be in the colliculus fascialis or distal to it, then facial paral- 

 ysis is complete. (5) At the same eminence, impulses pass into 

 the facial nerve from the hypoglossal nucleus via a small strand 

 of axones which rises in the hypoglossal nucleus and runs through 

 the medial longitudinal bundle into the facial at the genu (?). 

 These impulses innervate the orbicularis oris. (6) Through 

 certain short fibers in the medial longitudinal bundle which rise 

 in the nucleus of the sixth cerebral nerve and cross to the opposite 

 nucleus of the motor oculi, impulses run from the nucleus of the 

 abducent through the opposite third nerve to the internal rectus 

 oculi. They explain the conjugate action of the eyes in health, 

 and also the conjugate deviation observed in lesions affecting the 

 nucleus of the sixth nerve. In nuclear lesions of the abducent 

 nerve the external rectus of the same eye and the internal rectus 

 of the other eye are paralyzed if the nucleus is destroyed and 

 stimulated if the nucleus is only irritated. 



