248 A. G. POHLMAN 



columella has been severed. While the columellar-squamosal 

 ligament resists the pull of the M. tensor tympani, and therefore 

 is a passive agent in preventing outward displacement of the 

 drum, it also affords certain resistance to medial displacement 

 in the same manner that three toothpicks may be placed over 

 the opening of an ordinary drinking glass. This ligament is 

 indicated in figure 4 and is shown in figure 3. 



The columellar processes have, therefore, definite elastic liga- 

 ments associated with them. The infrastapedial attaches the 

 inferior drum-tubal ligament; the suprastapedial, the columellar- 

 squamosal ligament, and the extrastapedial, the middle drum- 

 tubal ligament. All of these ligaments are seen in a gross 

 dissection and the forces which bring about an increase in tension 

 may readily be demonstrated. 



Occasionally additional ligaments occur. Sometimes a deli- 

 cate elastic strand extends directly across the tympanum, from 

 the quadratosquamosal articulation to the drum proper, and 

 this may be regarded as an aberrant portion of the columellar- 

 squamosal ligament; more often the fibers of the inferior drum- 

 tubal ligament are projected up the length of the infrastapedial. 

 In spite of the close relation of the columellar-squamosa liga- 

 ment to the quadratosquamosal articulation, there does not 

 appear to be a transfer of motion from the quadratum to the 

 columella. With the exception of the middle drum-tubal hga- 

 ment, which is wanting or poorly developed in the pigeon, the 

 ligaments as described seem to hold for all birds examined — 

 chicken, duck, goose, turkey, and hawk. 



ELASTIC LIGAMENTS OF THE FENESTRA VESTIBULI AND 

 FENESTRA COCHLEAE 



The perilymphatic space of the inner ear is separated from the 

 cavum tympani at the fenestra vestibuli by the columellar foot- 

 plate which is held in place by an annular ligament, much in 

 the same manner as the basis of the stapes is attached by the 

 ligamentum annulare in the mammal. The margin of the foot- 

 plate practically fits the fenestra vestibuli, and the interval is 

 bridged by short stout elastic fibers, which permit a limited 



