MIDDLE-EAR REGION OF GALLUS 



237 



Turgescence of the pad might readily displace it forward and 

 outward and seal the external auditory canal, as Wurm has 

 suggested, but the position of its elastic fibers would indicate 

 that they are related to a pressure against the medial surface of 

 the pad and might therefore afford support to the drum mem- 



Fig. 1 Section through the dorsal limit of the drum membrane and external 

 auditory canal of an adult chicken; orcein stain. B, bursa; DM, drum marginal 

 elastic tissue; E, extrastapedial; EC, external auditory canal; EP, erectile pad; 

 I, infrastapedial. 



The stippled figures are drawn by Miss Gertrude Hance of St. Louis. 



Fig. 2 Oblique section through the dorsal region of an adult chicken; resorcin- 

 fuchsin stain. B, bursa; DM, drum marginal elastic tissue; E, extrastapedial; 

 MTS, membrana tympani secundaria; T, tympanum. 



brane or columella against a too-marked lateral excursion. 

 The elastic fibers would tend to draw the pad inward and back- 

 ward and assist in returning the blood into the jugular vein, or 

 would tend to bring the pad back to the normal position when 

 the drum membrane returns to its usual location. The glands 

 of the external auditory canal probably secrete a defensive mate- 



