Vr. THE MUSCULATURE OF THE EAR. 



Upon one of the foregoing pnges I liave already 

 described the circumconcha muscle, which I believe, 

 from my dissections, to be a constant one in the Raven. 

 By its contraction it evidently acts as a"laxator"to 

 the tympatinm. Careful search in a large number of 

 ears of this l)ird, however, fails to reveal to me any such 

 "tensor "as described by Professor Owen. I do find, 

 though, the following muscle : — 



48. Tensor tympani. — If we carefully dissect the 

 integument about the aural orifice in an old bird of this 

 species, we find a small fasciculus of muscular fibres that 

 arise from the inner end of the quadrato-jugal bone, and 

 the contiguous surface of the quadrate. These pass 

 beneath the integumental duplicature in the shallow 

 meatus, to be lost upon the inner surface of the tympa- 

 num. Now, as the drum is braced in the ear-j)assage 

 by at least two or three ligamentous bonds, more espe- 

 cially by a strong one above, it is very evident that, by 

 the contraction of such a muscle as I here describe, the 

 ear-drum would be put upon the stretch, and its tense 

 condition duly effected (Fig. 22, t.t.). 



In describing the tensor tynvpani in an Owl (Fig. 

 \Qi,f.), Professor Owen says : " It arises from a depression 



