CHAP. XVIII.] 



THE COCHLEARIS MUSCLE. 



79 



** "o. 



marked in the middle, and are again fainter ere they cease, which 

 they do at a curved line on the opposite side. Beyond this the 

 membranous zone is again clear, and homogeneous, and receives 

 the insertion of the cochlearis muscle. The inner clear belt of the 

 membranous zone is little affected by acids. It seems hard and 

 brittle. The middle or pectinate portion is more flexible, and tears 

 in the direction of the lines. The outer clear belt is swollen, and 

 partially destroyed by the action of acetic acid. Along the 

 inner clear belt, and on its tympanic surface, runs a single, some. 

 times branched vessel, which would be most correctly called a ca- 

 pacious capillary, as it resembles the capillaries in the texture of 

 its wall, but exceeds them in size. It is the only vessel supplied 

 to the membranous zone, and seems to be thus regularly placed, 

 that it may not mar the perfection of the part as a recipient and 

 propagator of sonorous vibrations. 



Of the Cochlearis Muscle. hi its 

 outer or convex margin, the mem- 

 branous zone is connected to the outer 

 wall by a semi-transparent struc- 

 ture. This gelatinous-looking tissue 

 was observed by Breschet, and is in- 

 deed very obvious on opening the 

 cochlea; but we are not aware of 

 any one having hinted at what we 

 regard to be its real nature. The 

 outer wall of the cochlear canal pre- 

 sents a groove, ascending the entire 



Coil, Opposite the OSSeOUS ZOne Of the 



lamina spiralis, and formed princi- 



pally by a rim of bone, which, in 



section, looks like a spur (fig. 137, r) , 



projecting from the tympanic margin the cochlearis muscle. 



of the groove, the opposite margin being very slightly or not at all 



marked. This groove diminishes in size towards the apex of the coch- 



lea. It gives attachment to the structure in question, by means of a 



firm dense film of tissue, having a fibrous character, and the fibres of 



which run lengthwise in the groove, and are intimately united to it, 



especially along the projecting rim. From this cochlear ligament, the 



cochlearis muscle passes to the margin of the membranous zone, filling 



the groove, and projecting into the canal, so as to assist in dividing the 



tympanic and vestibular scalse from one another, and thus forming in 



fact the most external, or the muscular zone of the spiral lamina. 



Inn e rvie wofcochlearismuscleofthesheep. 



