MIDDLE-EAR REGION OF GALLUS 247 



While birds undoubtedly close the tubal recess during the act 

 of swallowing, a direct relation of what corresponds to the rais- 

 ing of the soft palate and its effect on the cartilaginous tuba 

 auditiva in the mammals cannot obtain. This region demands 

 further study. It is interesting to note the relatively small 

 tubae auditivae of the bird, when compared with the relatively 

 large air-sinus system, and in figure 6 the confluence of the air- 

 sinus system may be noted in a twenty-day chick, which would 

 tend to show that air sinuses are a result of bone absorption 

 rather than a causal factor. 



COLUi\TELLAR-SQUAMOSAL LIGAMENT 



This ligament was also pictured by Breschet and described 

 by Platner ('39), hence commonly known as Platner's ligament. 

 It is a well-developed elastic band somewhat conical in form. 

 Its apex is attached to the suprastapedial and the common 

 cartilage stalk. It is directed forward, at right angles to the 

 columella, to become attached by a broad conical base at the 

 region of the quadratosquamosal articulation (fig. 11). While 

 it is usually described as attached to the quadratum, its strong 

 attachment appears to be to the squamosum, and it seems to 

 ride over the quadratosquamosal joint to become continuous 

 with the elastic tissue of the drum margin and with the elastic 

 ligaments of this articulation. It is sometimes well separated 

 from its bony attachment by an air-sinus opening. In very 

 young birds the ligament appears to be placed almost at right 

 angles to the position of the middle drum-tubal ligament, and 

 while the ligament is in part set in opposition to the pull of the 

 M. tensor tympani, its chief function seems to be to afford sup- 

 port to the extracolumella, so it may be considered a third mem- 

 ber of extracolumellar stability; the other two being formed by 

 the supra- and infrastapedials. All three of these members 

 are attached just medial to the drum margin and the three form 

 a somewhat elastic support to the extrastapedial which projects 

 beyond the plane of the drum margin and is therefore responsible 

 for the convexity of that membrane outward. This also accounts 

 for the fact that drum convexity is maintained when the bony 



JOURNAL OF MORPHOLOGY, VOL. 35, NO. 1 



