CHORDA TYMPANI. 



463 



torius, where the membrana tympani adheres to it, and uniting 

 to the neck of the malleus. It is supposed to draw the malleus 

 and membrana tympani upwards and forwards. This, how- 

 ever, is noticed by few authors. (It is called the Laxator 

 Tympani minor.) 



The stapes is also supplied with one muscle called the Sta- 

 pedius, which lies in the cavity of the pyramid. Its tendon 

 passes through the foramen in that protuberance, and is inserted 

 into the posterior part of the head of the stapes. It pulls the 

 head of the stapes upwards and backwards. 



Fig. 202.* Breschet, in an admirable 



g paper on the organ of hear- 



\ /' ing, after very careful researches 



on the subject, admits but 

 two muscles to the chain of 

 bones, the tensor tympani or 

 internus auris, and the stape- 

 dius, which he calls laxator 

 tympani. In birds, there is but 

 "/one muscle attached to the 

 \ chain of bones, and that is a 



\ tensor of the tympanum. In 



C b reptiles, even when the chain of 



with, Breschet was unable to discover a 



a 



bones was met 

 single muscle. 



The Chorda Tympani. 



In the upper and posterior part of the cavity of the tym- 

 panum is a small nervous chord which enters by a foramen 



* Fig. 202, is a magnified representation of the cavity of the tympanum, 

 and its chain of bones, a, a, Cavity of the tympanum, b, Membrani tym- 

 pani. c, Manubrium of the malleus, the end of which is attached to the mid- 

 dle of the membrani tympani. d, Head of the malleus articulated with the 

 incus, e, Processns gracilis, arising below the neck of the malleus, and extend- 

 ed into the glenoidal fissure of the temporal bone $ upon its extremity is inserted 

 the laxator tympani muscle of the malleus, if it really exist. /, Tensor tym- 

 pani muscle, g, Incus, the horizontal short leg of which is placed in the cavity 

 leading to the mastoid cells, the long vertical leg of which is articulated with 

 the os orbiculare, h. i, Stapes, the top of which is articulated with the os orbi- 

 culare, and the base rests upon the membrane, closing the fenestra ovalis. 

 k, Stapedius muscle. 



