96 FRANKLIN PEARCE REAGAN 



which was left behind assumed a spherical form. When the 

 embryo was sectioned it was found that this hollow sphere of 

 epithelium occupied a position symmetrical with the distal ex- 

 tremity of the lagena of the uninjured side, possessing like the 

 latter, a cartilaginous capsule which appeared as a rounded 

 projection of the parachordal cartilage. The displaced portion 

 of the otocyst (figs. 5 and 9) may be interpreted as utriculus 

 with perhaps a portion of the sacculus. The anlage of the 

 endolymphatic duct, and in all probability a portion of the 

 utriculus were destroyed. The remainder of the displaced epi- 

 thelium, together with the intimately related acoustico-facialis 

 ganglion are found to have occupied and dilated the foramen in 

 the cartilage which is normally occupied by the geniculate 

 ganglion and traversed by the facial nerve. 



Figure 4 is a photograph of the normal side of a frontal sec- 

 tion through the columellae of the embryo just described. 

 The figure requires no explanation beyond that given for figure 

 2. Its chief value lies in the fact that it affords a comparison 

 of the normal stapes with that of the operated side. The con- 

 ditions of the latter are shown in figure 5, which is from the oppo- 

 site side of the same section from which figure 4 is taken. The 

 columella on the operated side resembles in size, shape, and 

 position, that of the normal side. Auditory epithelium does not 

 appear in this plane of section on the noral side. There is no 

 otic capsule in this section. Coincident with this fact is that 

 of the absence of a stapedial plate. It will be noted that two 

 cartilages are present around the exit of the facial nerve. The 

 more ventral one has a dorso-ventral direction, its lower end 



Figs. 4 and 5 Photographs of the otic region of a nine-day chick embryo 

 in which the right otocyst was early displaced into the region of the future exit 

 of the facial nerve. Both figures lie in the same transverse plane. Figure 4 

 is through the normal side. Figure 5 is through the operated side. It shows 

 the ventral-most portion of the displaced otocyst together with the facial nerve. 

 These are frontal sections. P. E. C. No. 1118. Aud., auditory nerve; Col., 

 columella; E.a.m., external auditory meatus: E. Col., extra-columella; Fac, 

 facial nerve; G.^., trigeminal ganglion; GL, glossopharyngeal; Int. car., internal 

 carotid; Otcst., otocyst; Par., parachordal; Qudr., quadrate; .S^/., squamosal; 

 St. p., stapedial plate. 



