434 



George L. Streeter, M.D. 



their general form, the various parts of the labyrinth exhibit at 

 this time individuality. (See Fig. 4.) The ventro-median portion 

 of the vestibular sac and the ampullar ends of the semicircular 

 canals possess high columnar cells forming the neuro-epithelial 

 maculae which are supplied with fibers from the acoustic ganglion, 

 lying against the medial wall of the labyrinth. The endolymphatic 

 sac has cuboidal cells, and the lagena has intensely staining col- 

 umnar cells like those seen in the macular regions. The lagena 

 is further characterized by its sharply rounded outline, and by the 

 fact of its being compactly surrounded by ganglion cells and fibers, 

 and cartilage forming cells. These features are so definite that 



Crus commune 



Sac . endol 

 C . sc. posterior 



C. sc. anterior 



X-IX-' 



, . . 'Gang, prooiic. 



C.5C. lateral is 



Fig. I Reconstruction showing the form and relations of the membranous labyrinth of a normal 

 tadpole (Rana pipiens)one month old. The labyrinth, adjacent ganglia and part of the brain were 

 reconstructed after the Born method, and the remainder of the figure was drawn from a dissec- 

 tion of a tadpole of the same age. Enlarged 35 diameters. 



the various parts of the labyrinth can be recognized without diffi- 

 culty, even though they happen to be incomplete, or out of their 

 normal relations. 



Now if one examines the models of the operated specimens, 

 photographs of three of which are reproduced in Fig. 2, it is seen 

 that the individuality of the semicircular canals can at once be 

 identified. In model a, the canals are practically normal; in model 

 b, the anterior canal is small, and the lateral canal consists only 

 of a pouch which has not been pinched off from the main cavity; 

 in model r, the posterior canal remains a simple pouch, while the 



