100 FRANKLIN PEARCE REAGAN 



side is represented on the operated side by a narrower 

 parachordal. 



Figure 6 represents the normal region in a section of the same 

 embryo, through the head of the columnella. It shows the rela- 

 tion of the facial nerve and its capsule. Figure 7 represents the 

 operated side in the same plane of section as that of figure 6; 

 the acoustico-facialis ganglion lies against the lower extremity of 

 the otocyst. Sections in this region studied progressively 

 towards the dorso-posterior region reveal the cavity of the 

 transplanted portion of the otocyst. It is not difficult to see 

 that the otocyst here occupies the foramen for the facial nerve, 

 and that the acoustic and facial ganglia still preserve their 

 intimacy of connection. 



Figure 8 shows the normal side of a section somewhat dorsal 

 to the plane of section of figures 6 and 7. The proximal portion 

 of the facial nerve is seen entering its capsule on the mesial 

 surface of the latter. Laterally this capsule is joined by the 

 otic process of the quadrate. In the abnormal portion of this 

 same section (fig. 9) one sees the capsule of the facial ganglion 

 and nerve occupied by the sac-like otocyst; the latter more than 

 fills the cavity at the inner entrance to the capsule and projects 

 out into the scant mesenchyme between the cartilage and the 

 brain-wall. Inside the capsule the sensory epithehum is sur- 

 rounded by a vascular plexus. Where the auditory epithelium 

 projects mesially towards the brain wall, it is internally covered 

 by a perichondrium-like condensation of the adjacent mesen- 

 chyme which is continuous with the perichondrium of the carti- 

 laginous capsule. Lateral to this capsule will be seen the otic 

 process of the quadrate together with the overlying squamosal. 

 In sections still more dorsad, the otic process of the quadrate 

 is fused with the cartilaginous capsule surrounding the epithe- 

 lial sac indicating the comparability of this cartilage to that of 

 the unoperated side through which the facial nerve courses. 



Figs. 8 and 9 Frontal sections through the region of the facial ganglion 

 of this same nine-day embryo. On the normal side the facial ganglion (fig. 8) 

 is shown. Figure 9 is the abnormal side of the same section in which the car- 

 tilage which would normally have surrounded the facial ganglion surrounds 

 the entire otocyst. (Abbreviations as in previous figures. P. F;. C. No. 1118.) 



