MIDDLE-EAR REGION OF GALLUS 243 



the columella are of some little importance in interpreting the 

 mechanics of the columellar system, and will be referred to later. 



DRUM-TUBAL LIGAMENTS 



Medial inspection of the drum membrane, particularly in a 

 specimen stained in toto with orcein and differentiated in alcohol, 

 reveals a series of elastic ligaments which were pictured by 

 Breschet and rediscovered by Smith, although neither inves- 

 tigator apparently understood their nature or function. These 

 ligaments may well be named the drum-tubal ligaments and 

 described in drum and tubal segments. The superior and 

 middle drum-tubal ligaments arise from a common strand of 

 elastic tissue in the lateral wall of the tuba auditiva and in close 

 relation to the drum margin. The superior ligament joins the 

 drum margin and runs upward, contributing to the medial elastic 

 wall , of the drum marginal sinus. It may be traced to the 

 quadratosquamosal joint or to the foramen pneumaticum for 

 the quadratum. 



The smaller segment, the middle drum-tubal ligament (fig. 4), 

 is the pearly streak of Breschet, and is readily observed in most 

 birds, and in all instances is distinctly fused to the drum tissue 

 and not independent in the turkey, as Breschet described it. 

 It terminates in the tip of the extrastapedial and forms a very 

 obtuse angle with the line of the pull of the M. tensor tympani 

 on this process. It seems to become less markedly developed as it 

 passes across the drum surface. 



The inferior drum-tubal ligament arises from the floor of the 

 tuba auditiva, and while it contributes some fibers to the inferior 

 drum margin, the major portion passes across the edge of the 

 drum to terminate in the tip of the infrastapedial which, it will 

 be recalled, does not quite reach the edge of the drum. This 

 ligament is ordinarily better developed than the other two 

 combined (not shown in figure 4). 



The tuba auditiva therefore presents two elastic strands near 

 the drum margin, the inferior drum-tubal ligament and the 

 fused superior and middle drum-tubal ligaments. These two 

 join to form a common elastic bundle before the tuba has crossed 



