174 GEORGE L. STREETER 



side of the brain wall. This tendency to an early nerve-ganglion 

 connection between the ear vesicle and some portion of the brain 

 wall is evident even when the vesicle is transplanted in a strange 

 environment such as in front of the eye (Streeter '06). The nerve 

 seeks the brain wall, and is it conceivable that after it is securely 

 attached it would act as a check or guy rope on the vesicle. With 

 the subsequent growth and the change in the relative positions 

 of the different structures, the nerve attachment would pull on 

 it and, depending on its previous position, would tend to rotate 

 it one way or another. When the vesicle is in front of the eye 

 there are so many abnormal factors present that one could not 

 expect a successful correction of posture through this means. But 

 in the auditory region where other things are favorable it is con- 

 ceivable that the nerve attachment might at least help in the 

 adjustment of the position of the vesicle. As a modification of 

 this idea it is conceivable that there exists some mutual attraction 

 between the macula, ganglion, and brain wall which tends to 

 draw them together by some psysico-chemical process. This 

 would result in the same effect on the labyrinth as a whole as a 

 tension of the acoustic nerve, and would serve in the same way as 

 an assisting force in the adjustment of the position of the vesicle. 

 In an analogous way it is possible that the endolymphatic append- 

 age may be attracted to the side of the brain wall and thus tend 

 to draw the vesicle into position. Wherever the endolymphatic 

 duct and sac are well formed there exists a constant relation 

 between them and the brain which I have never heretofore seen 

 mentioned. The endolymphatic sac always lies closely applied 

 to the membranous roof of the fourth ventricle near the rhombic 

 lip. Some force may bring these two structures together, and 

 thus we would have a secondary correcting influence on the 

 posture of the whole vesicle. This, it must be admitted, cannot be 

 the whole explanation, as we have vesicles with correct posture in 

 cases where the endolymphatic sac is entirely absent. 



As a third possibility there is to be considered, from a purely 

 mechanical standpoint, the shape of the vesicle and the bed or 

 pocket in which it fits. The auditory pocket is bounded on the 

 median side by the relatively firm brain wall, ventrally by the 



