635 THE EAE, 



wards to near its point, where it is flattened laterally : it descends, -with 

 a slight inclination forwards and inwards, between the middle and inner 

 layers of the menibrana tyrapani, to the former of whicli it is closely 

 attached both by means of its periosteal covering and also by a dense 

 fibro-cartilaginous tissue extending its whole length, except near the root 

 of the process, where it is less firmly united to the membrane. The 

 long process (processus gracilis) (fig, 448, a, 3) is a very slender spiculuni 

 of bone, which in the adult is usually converted, except a small stump, 

 into ligamentous tissue. Even where it still exists it is commonly 

 broken off in its removal from the tympanum, in consequence of its 

 union with the temporal bone ; it projects at nearly a right angle 

 from the front of the neck of the malleus, and extends thence obliquely 

 downwards and forwards to the Glaserian fissure. Its end is flattened, 

 and expanded, and is connected by ligamentous fibres and by bone to 

 the sides of the fissure. The short process (processus brevis vel obtusus) 

 (fig. 448, A, 4) is a low conical eminence situate at the root of the 

 manubrium, beneath the cervix, and projecting outwards towards the 

 upi^er part of the membrana tympani. 



The incus (fig. 448, b), has been compared to an anvil in form ; but 

 it resembles perhaps more nearly a tooth with two fangs widely sepa- 

 rated. It consists of a body and two processes. The liochj presents in 

 front a concavo-convex articular surface (4), which is directed upwards 

 and forwards, and receives the head of the malleus. The surfaces of 

 the joint thus formed are covered with articular cartilage and enclosed 

 by a synovial membrane. The sliortcr of the two processes (crus breve) 

 (3), of the incus projects nearly horizontally backwards from the upper 

 part of the body of the bone, and is connected by ligamentous fibres 

 with the posterior wall of the tympanum near the entrance of the 

 mastoid cells. The long 'process (crus longum) (2) tapers rather more 

 gradually, and descends nearly vertically behind the handle of the 

 malleus : at its extremity it is bent inwards, and is suddenly narrowed 

 into a short neck ; and upon this is set a flattened rounded tubercle 

 (processus lenticularis), tippsd with cartilage. This tubercle, Avhich 

 articulates with the head of the stapes, was formerly, under the name 

 of OS orliculare sen lenticulare, described as a separate bone, which 

 indeed it originally is in childhood. 



The stapes (fig. 448, C), the third and innermost bone of the ear, is 

 in shape remarkably like a stirrup, and is composed of a head, a base, 

 and two crura. The head is directed outwards, and has on its end a 

 slight depression, covered with cartilage, which articulates with the len- 

 ticular process of tlie incus. The hcise is a plate of bone placed in the 

 fenestra ovalis. Its form is irregularly oval, the upper margin 

 being curved, while the lower is nearly straight (fig. 448, C*). Its 

 border is encircled by hyaline cartilage, which also covers its vesti- 

 bular surface. The margin of the fenestra ovalis has also a cover- 

 ing of the same tissue, and the opposed cartilaginous surfaces are 

 closely connected, and their movement of the stapes is limited by a 

 network of elastic fibres passing between, and, near the tympanic and 

 vestibular cavities, forming especially a dense ligamentous band 

 (Riidinger). The crura of the stapes diverge from a constricted part 

 (nech) of the bone, situated close to the head, and are attached to the 

 outer surface of the base near its extremities. The anterior crus is 

 the shorter and straighter of the two. The crura, with the base of the 



