THE MIDDLE EAR. 



1497 



The malleus (hammer) is about 8 mm. long and consists of a head, a neck and three 

 processes. The head is the upper club-shaped portion, lying in the epitympanic space ; the 

 constricted portion just below the head is the neck, and below this is a prominence to which 

 the three processes are attached. The posterior surface of the head bears, for the articulation 

 with the incus, an oblong depressed surface with prominent margins extending in a spiral 

 manner downward and inward to the neck. This articular surface consists of two principal 

 facets separated by an oblique ridge, the upper facet looking backward, the lower, inward. 

 The axis of the head forms with that of the handle an angle of about 140°, opening upward 

 and inward. 



Fig. 1255. 



Head 



Neck 



Point of insertion of 

 lateral ligament 



Articular 

 surface for 

 incus 



Head 



Processus 

 brevis 



Manubrium 



Processus 



brevis 



Manubrium 



Processus gracilis 



Right malleus ;.f4, seen from behind; i^, sec'n from in front. X 4J^. 



The manubrhnn (handle), a tapering process extending downward, backward and inward, 

 is embedded in the substance of the tympanic membrane (Fig. 1258). Near the upper part 

 of the inner anterior surface of the handle is sometimes found a slight projection for the 

 insertion of the tensor tympani muscle. The lower end of the manubrium is spatula shaped, 

 flattened transversely. The long process is directed toward the Glaserian fissure, whilst the 

 short process looks toward the external meatus. 



T\\Q. processus breins (short process) is a small conical elevation situated at the upper end 

 of the handle, below the neck of the malleus. Like the handle it is attached to the tympanic 

 membrane and covered by a layer of cartilage, notably on its external surface. 



The processus gracilis (long process) arises from the anterior angle of the internal surface 

 of the neck, close to the base of the short process, and extends downward and forward to the 

 Glaserian fissure. It is well developed in the fcetus and in young children, but is often rudi- 

 mentary in the adult. 



Fig. 1256. 



n 



Bodv 



Processus 

 brevis 



Upper facet 



Lower facet 



Processus 



101ig"ii3 



Upper facet 

 Lower facet 



Processus longus 



^ _ Processus 

 brevis 



Processus 

 orbicularif 



Right incus; A, lateral; B, anterior aspect. "X 4^. 



The incus ( anvil ) resembles a molar tooth with two widely separated fangs, rather than an 

 anvil. It consists of a body, a long process and a short process. The body of the incus has 

 two main facets on its anterior and antero-external surfaces, which correspond to those on the 

 head of the malleus and articulate with them. The processus brevis (short process) is conical 

 in shape, flattened laterally and projects nearly horizontally backward to a depression in the 

 posterior wall of the tympanum at the entrance of the antrum, where its apex is attached. The 

 processus loiigus (long process) runs downward and backward, behind and nearly parallel with 

 the handle of the malleus, and forms nearly a right angle with the short process. At its lower 

 end it is bent sharply inward and constricted into a neck, which terminates in a rounded 

 tubercle, the processus orbicularis, that articulates with the head of the stapes. In the fcetus 

 this process is separated from the rest of the long process. 



