474 



CALCAREOUS CONCRETIONS IN THE LABYRINTH. 



down the scala vestibuli, and be felt both in the vestibulum 

 Fig. 204.* and semicircular canals. In 



the same manner the action 

 of the chain of bones upon 

 the foramen ovale, would 

 be felt through the entire 

 labyrinth. 



It has been suggested that 

 the two foramina, (ovale 

 and rotundum,) are provid- 

 ed for the purpose of render- 

 ing more complete the trans- 

 mission of the vibration of 

 the membrana tympani. 

 One is acted on by the 

 chain of bones, the other 

 by the air of the tympanic 

 cavity ; both at the same 

 time causing movements in 



* Fig. 204, is a magnified view of the bony labyrinth of the right side of 

 the body, with the membranous labyrinth (consisting of semicircular tubes, 

 median or utricular sinus sometimes called sacculus ellipticus and sacculus spheri- 

 cuSf) pulverulent concretions, and the termination of the nerves. The two scala 

 of the cochlea are also seen, as well as their openings into the vestibule and 

 into the cavity of the tympanum. The bony labyrinth is represented as cut 

 open, showing the membranous labyrinth. All the parts marked with the 

 asterisks (**) are filled with the lymph of Cotunnius. 0, Ampulla of the 

 anterior or semicircular canal, b, Ampulla of the internal semicircular canal, 

 c, Ampulla of the posterior semicircular canal, d. Anterior membranous semi- 

 circular canal, e, External membranous semicircular canal. /, Posterior 

 membranous semicircular canal, g, Common membranous canal resulting 

 from the junction of the anterior and posterior canals, d and/, h, Place where 

 the semicircular canal opens into the utricular or median sinus, i, i, Utricular 

 or median sinus, filling a greater part of the vestibule, and exhibiting through 

 its walls a mass of calcareous powder at h, (otoconie utriculaire.) I, /, Sac 

 containing also a mass of calcareous powder at m, (otoconie sacculaire.) n, Ner- 

 vous fasciculus, forming an expansion, o, on the ampulla of the anterior canal ; 

 another, p, on that of the external ; and a third, q, on the sinus utriculosus. r, 

 Nervous fasciculus distributed on the sac. v, Nervous fasciculus distributed 

 on the posterior ampulla, s, s, Lamina spiralis. s, End of the lamina, form- 

 ing its hamulus or hook, t, Commencement of the scala tympani near the 

 fenestra rotunda, which is not shown here. ,M, Commencement of the scala 

 vestibuli. x, Modiolus or column, round which is wound the lamina spiralis. 



