THE SKULL THE CKANIILM 



223 



FIG. 155. 



ward, and outward again. Where the neck joins the handle on the 

 anterior side a slender rod, known as the long process, projects forward 

 and slightly upward. The upper margin of this process is connected 

 with the anterior edge of the neck and the lower part of the head by 

 means of a thin lamina of bone, often broken in removing the ossicles 

 from the tympanum. The pointed end of the long process fits into a 

 pit (Fig. 151) in the under surface of the ectotympanic, to which 

 surface the thin free margin of the lamina also is attached by mem- 

 brane. Where the neck, the handle, and the long process meet on the 

 inner side of the bone (Fig. 152) is the point of origin of a small 

 process which curves forward and upward and affords attachment for 

 the tendon of the tensor tympani muscle. 



The handle of the malleus is almost straight, or gently concave 

 forward, and turned slightly outward at the lower end. In its upper 

 part it is prismatic, presenting outer, 

 anterior, and posterior surfaces ; in its 

 lower part it is compressed from within 

 outward, and hence presents only inner 

 and outer surfaces. The outer surface 

 (Fig. 154) is long, narrow, and flat ; 

 it is fastened to the tympanic mem- 

 brane. Its upper end projects higher 

 than the other surfaces and forms an 

 external heel which is known as the 

 short process. The anterior surface 



(Fig. 155) is Avide, excavated above and narrow below where it becomes 

 continuous with the posterior, surface. The posterior surface (Fig. 

 153) resembles the anterior surface, but is not excavated above ; it is 

 separated from the neck and from the process for the tensor tympani 

 muscle by a wide, oblique groove. 



The Incus l (Fig. 156) is much smaller than the malleus, measuring 

 but two millimetres in length and three millimetres in height. It has 

 the shape of a tooth with two diverging fangs. 



The anterior surface of the head, the surface which corresponds 

 to the crown of a tooth, is occupied by a cavity for articulation with 

 the head of the malleus. This cavity encroaches slightly on the outer 

 nspect of the bone. Like the cavity on the head of the malleus, it is 



Head.- 4 



Lamina. 



Process for TENSOR 



TYMPANI. 



,. Short Process. 



'--- Handle. 



LEFT MALLEUS. ANTERIOR ASPECT. 

 (Enlarged Five Times.) 



1 An anvil. 



