94 THE MEMBRANOUS LABYRINTH, BY PROF. RUDINGER. 



labyrinth and the periosteum in the Frog is by no means so 

 intimate as in Birds, Mammals, and Man ; a relation that may 

 possibly be regarded as dependent upon the degree of regressive 

 metamorphosis undergone by the gelatinous tissue. 



-2. WALL OF THE LABYRINTH. 



The histology of the wall of the labyrinth is most advan- 

 tageously studied in transverse sections. The semicircular canal, 

 which is oval or transverse in s-ection, appears to be of unequal 



Fig. 302. 



Fig. 302. 

 from Man. 



Transverse section of a membranous semicircular canal 

 1, Free portion of the wall, with the fibrous layer and 



connective-tissue corpuscles ; 2, tunica propria ; 3, papillse, with 

 their epithelium ; (4, omitted ;) 5, portion of the wall free from pa- 

 pillae, with a thin layer of the tunica propria ; 6, strongly developed 

 papillse at the boundary of the portion destitute of papillse ; 7, liga- 

 menta labyrinthi canaliculorum. 



thickness. (See fig. 302.) In the semicircular canals of Man, the 

 thickness of the wall where attached to the bone, exclusive of 

 the periosteum, is 0*016 of a millimeter ; the free wall measures 

 0'028, and 'at the points where it is fixed by the ligamenta 

 labyrinthi canaliculorum it has a diameter of 0'060 O'OSO of a 

 millimeter. 



Four layers of tissue may be distinguished in the wall of the 



