HISTOLOGY OF THE MEMBRANOUS LABYRINTH. 93 



solid wall. The relatively wide cartilaginous or osseous canal 

 is here partially filled by a plexus of broad fibrous trabecula?, 

 which enclose a system of cavities filled with mucus. The rest 

 of the space is occupied by the membranous canal which is 

 loosely adherent to the wall, and by a fine fibrous plexus that 

 does not essentially differ from the above-mentioned gelatinous 

 tissue in the canals of the human foetus and of the Frog. 



In his first communications on the Frog, Hasse made the 

 following statement, that he had observed certain markings on 

 the outer surface of the membranous canals in this animal, 

 which gave the impression of the presence of an epithelial 

 investment. But transverse sections made through the mem- 

 branous labyrinth whilst still adherent to the bone show 

 histological relations (especially well marked in the osseous 

 semicircular canals) which thoroughly negative the existence 

 of a serous layer; for if successful sections be examined, we 

 may perceive that the anastomosing connective-tissue cor- 

 puscles which completely fill the canal, and which in the 

 human embryo we have termed gelatinous tissue, are persistent 

 in the Frog. Whether they remain in this condition throughout 

 the whole of life I am unable to say, since my researches have 

 only been made on Frogs at the end of the winter. 



In the gelatinous tissue in the Frog I find also many large 

 pigment cells, of which a few adhere intimately to the outer 

 side of the membranous canals. A still richer deposit of pig- 

 ment exists in the neighbourhood of the utriculus and of the 

 otolithic sac in the vestibule, so that the point of entrance of 

 the nerves and vessels into the utricular wall is rendered some- 

 what obscure. In regard to the support received by the walls 

 of the membranous labyrinth of the Frog, it is to be remarked 

 that the utriculus, the otolithic sac, the ampullae, and the com- 

 mencement of the membranous canals lie tolerably close to the 

 dense capsule ; but, on the other hand, it cannot be denied that 

 the membranous semicircular canals, where they are most, re- 

 mote from the vestibule, become detached from the wall of the 

 osseous canal, so that they appear to be everywhere surrounded 

 by nucleated finely fibrous connective tissue. Should any one 

 be disposed to regard this as a result of manipulation, he should 

 not forget that the connection between the entire membranous 



