208 LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



the acoustic nerve with the nerves governing the movements of 

 the eye. It may be of importance in connection with our judg- 

 ment of space measurements. 



External to the dorsal acoustic nucleus, imbedded in the 

 direct sensory cerebellar tract, lies a nucleus -whose significance 

 is wholly unknown. It was formerly called the external acoustic 

 nucleus. It atrophies if the cervical cord is divided on the 

 same side (Monakow). No connection between it and the nerves 

 of hearing has- been clearly shown. It is, therefore, better for 

 the present to call it Deiters' nucleus, in honor of that great 

 investigator of the medulla oblongata. 



The method of origin of the acoustic nerve, which was 

 long in doubt, has been the subject of study by a number of 

 investigators. The results obtained by some do not agree with 

 the statements which have been made here, and which are based 

 on personal research. 



The author and Freund, whose investigations were con- 

 ducted upon human embryos, have arrived at practically the 

 same conclusions. Bechterew and Flechsig contend that the 

 anterior root does not arise from the dorsal nucleus, but rather 

 from some cells situated in the vicinity of Deiters' nucleus. .The 

 origin of the posterior roots from the ventral nucleus is conceded 

 by all. Tearing out the acoustic nerve results in atrophy of 

 this nucleus (Forel, Onufrowics, Baginski). 



Let us, before we go farther, again look up the structures 

 of the tegmentum which have not been specially mentioned in 

 the text, and ascertain their situation and form at these levels. 

 One, the nucleus reticularis tegmenti, which, together with the 

 fibres of the substantia reticularis, is spread out over the area 

 between the raplie and the root of the facial nerve, has, for the 

 sake of clearness, been omitted from the illustrations. We 

 could have seen it in all the sections through the levels which 

 we have been studying. 



The following figure (Fig. 126) represents the section lying 

 just ahead of the preceding one, and is only given to show how 



