THE SEXSES. 



569 



The ossicles or small bones of the ear are three, named Malleus, 

 Incus, and Stapes. The Malleus, or hammer-bone, is attached by a 

 long, slightly-curved process, called its handle, to the membrana tym- 

 pani; the line of attachment being vertical, includ- 

 ing the whole length of the handle, and extending 

 from the upper border to the centre of the mem- 

 brane. The head of the malleus is irregularly 

 rounded; its neck, or the line of boundary between 

 it and the handle, supports two processes; a short 

 conical one, which receives the insertion of the 

 tensor tympani, and a slender one, processus gra- 

 cilis, which extends forwards, and to which the 

 laxator tympani muscle is attached. The incus, 

 or anvil-bone, shaped like a bicuspid molar tooth, 

 is articulated by its broader part, corresponding 

 with the surface of the crown of a tooth, to the 

 malleus. Of its two fang-like processes, one, di- 

 rected backwards, has a free end lodged in a de- 

 pression in the mastoid bone; the other, curved 

 downwards and more pointed, articulates by means 

 of a roundish tubercle, formerly called os orbicu- 

 lar -e, with the stapes, a little bone shaped exactly 

 like a stirrup, of which the base or bar fits into the 

 fenestra ovalis. To the neck of the stapes, a short 

 process, corresponding with the loop of the stir- 

 rup, is attached the stapedius muscle. 



" The ossicula of aquatic mammalia are very bulky and relatively 

 large, especially in the true seals and the sirenia (Manatee and Dugongj. 

 In the cetacea the stapes is generally ankylosed to the fenestra ovalis, 

 the malleus is always ankylosed to the tympanic bone, yet the membrana 



FIG. 379. Outer sur- 

 face of the pinna of the 

 right auricle. 1, helix; 2, 

 fossa of the helix; 3, anti- 

 helix; 4, fossa of the an- 

 tihelix; 5, antitragus; 6, 

 tragus; 7, concha; 8, 

 lobule. %. 



FIG. 380. 



FIG. 381. 



FIG. 382. 



FIG. 380 The hammer-bone or malleus, seen from the front. 1, The head; 2, neck; 3, short pro- 

 cess; 4, long process. (Schwalbe) 



FIG. 381. The incus, or anvil-bone. 1, body; 2, ridged articulation forthe malleus; 4, processus 

 brevis, with 5, rough articular surface for ligament of incus; 6, processus magnus, with articulat- 

 ing surface for stapes; 7, nutrient foramen. (Schwalbe.) 



FIG. 382. The stapes, or stirrup-bone. 1, base; 2 and 3, arch; 4. head of bone, which articulates 

 with orbicular process of the incus; 5, constricted part of neck; 6, one of the crura. (Schwalbe.) 



tympani is well formed, and there is a manubrium, often ill-developed, 

 but always attached to the membrane by a long process. In the Otariae or 

 Sea-lions, where the ossicula are far smaller relatively, and less solid than 

 in whales, manatees, and the earless true seals, there are well-formed, 



