162 GEORGE L. STREETER 



figure 16. The posterior region is defective in that the posterior 

 canal and cms commune consist of a common pouch, taking how- 

 ever the usual shape of the posterior canal. The lagena devel- 

 oped as a pair of short pockets, one extending medially and the 

 other caudally. Apparently the anlage was divided. The 

 endolymphatic sac (figure 15) presents the usual relation to the 

 chorioidal membrane. 



Labyrinth IX: (figures 17 and 18). The photograph shown in 

 figure 17 is taken from Series X 8 A, slide 2, row 4, section 9. 

 It passes through the endolymphatic sac, the crus commune, and 

 the vestibule with the lateral canal opening into it. In the sections 

 oral to this the lateral canal becomes completely separated, though 

 it is small and is deficient in the region of the ampulla. The 

 anterior canal is small but well formed. The posterior canal is 

 completely formed but lies closely against the vestibular wall. 

 The vestibule is small throughout and lacks the lagena. The 

 acoustic ganglion is well developed and is connected with the 

 brain in the normal way. The endolymphatic sac (fig. 17) 

 bears the usual relation to the chorioidal membrane. This is the 

 first of what we have grouped as abnormal labyrinths. 



Labyrinth X: {figures 19 and 20). The photograph shown in 

 figure 19 is taken from Series X 11 C, slide 1, row 2, section 8. 

 In this labyrinth the injury involves the endolymphatic appendage 

 and the anterior canal. The latter exists as a blind pouch ex- 

 tending orally from the crus commune. This should be compared 

 with figures 26 and 28, where a similar defect involves the posterior 

 canal. The remainder of the labyrinth is quite perfect. Figure 

 19 shows the crus commune, the vestibule, with a portion of the 

 acoustic ganglion, and the lateral canal. The endolymphatic 

 appendage is entirely absent. 



Labyrinth XI: {figures 21 and 22). The photograph shown in 

 figure 21 is taken from Series X 8 B, slide 2, row 2, section 8. 

 Here there is considerable abnormality in the ventral half of the 

 labyrinth, and the labyrinth is correspondingly reduced in size. 

 The anterior and posterior canals and the endolymphatic sac 

 are fairly normal. In figure 21 can be seen the endolymphatic 

 sac with its usual relation to the chorioidal membrane. The 



