. 



ENDOLYMPH. PERILYMPH. 473 



branous and bony canals. It is asserted by Brugnone and 

 Ribes, that the lymph but partly fills the cavity in its natural 

 condition ; but Breschet,* from elaborate researches in man and 

 a variety of vertebrated animals, declares this to be an error.f 

 The membranous structure is afloat as it were in this fluid, 

 and is affected by the slightest impulse communicated to the 

 fluid, through the membrane closing the foramen rotundum 

 and foramen ovale, with which the fluid is in contact. The 

 fluid of the membranous labyrinth is denser in fish than in land 

 animals. M. E. Barruel has examined it chemically in the 

 great seal, (Squalus Cat. L.) He found it viscous and transpa- 

 rent, containing a matter floating in it, which when dried formed 

 a calcareous powder. 



For the sake of clearness of description, Breschet proposes 

 to call the fluid within the membranous labyrinth the endo- 

 lymph ; that between if and the bony labyrinth the perilymph. 

 The auditory nerves terminate in delicate villi, which project 

 in the cavities filled by the endolymph ; and in order to give 

 the sonorous impulse transmitted from without more effect 

 upon the nerves, there is placed in the cavity of the labyrinth 

 from one to three calcareous substances which are thrown into 

 agitation by the impulse. These have been long known to 

 exist in the ears of osseous fishes, as small concretions of car- 

 bonate of lime, see fig. 203, called otoliths ; and Breschet has 

 found them invariably in the state of granular powder which 

 he calls otoconie,\\ in man, the three upper classes of verte- 

 brated animals, and in cartilaginous fishes. The cavity in 

 which the perilymph is contained in the cochlea, vestibule 

 and semicircular canals, is continuous, so that an impulse 

 transmitted through the membrane of the foramen rotundum, 

 would pass along the scala tympani across the infundibulum, 



* Recherches Anatomiques et Pathologiques sur 1' Organs de 1' Ouie et sur 

 1' Audition, dans 1' Homme et les Animaux Vertebres ; par G. Breschet. Me- 

 moires de V Academie Royale de Medecine ; torn. v. 



f Cotugno and P. F. Meckel held the same opinions as Breschet. 



| Ovf, WTO?, ear ; \iGos, stone. fl Oros, K ovis, swp f , powder, dust, etc. 



40* 



