VOL. LXXVII.] PHILOSOPHICAL TRANSACTIONS. 343 



length, is firm in texture, with thick coats, is hollow on its inside, and its 

 mouth communicating with the tympanum; one side being fixed to the malleus 

 similar to the tendinous process which goes from the inside of the membrana 

 tympani in the others. 



A little way within the membrana tympani, are placed the small bones, which 

 are 3 in number, as in the quadruped, malleus, incus, and stapes; but in the 

 bottle-nose whale there is a 4th, placed on the tendon of the stapedaeus muscle. 

 These bones are as it were suspended between the bone of the tympanum and 

 that of the immediate organ. The malleus has 2 attachments, besides that with 

 the incus; one close to the bone of the tympanum, which in the porpoise is only 

 by contact, but in others by a bony union; the other attachment is formed by 

 the tendon, above described, being united to the inner surface of the membrana 

 tympani. Its base articulates with the incus. The incus is attached by a small 

 process to the tympanum, and is suspended between the malleus and stapes. 

 The process by which it articulates with the stapes is bent towards that bone. 

 The stapes stands on the vestibulum, by a broad oval base. In many of this 

 tribe, the opening from side to side of the stapes is so small as hardly to give the 

 idea of a stirrup. 



The muscles which move these bones are 2 in number, and tolerably strong. 

 One arises from that projecting part of the tympanum which goes to form the 

 eustachian tube, and running backwards is inserted into a small depression on the 

 anterior part of the malleus. The use of this muscle seems to be to tighten the 

 membrana tympani; but in those which have the malleus anchylosed with the 

 tympanum, we can hardly conjecture its use. The other has its origin from the 

 inner surface of the tympanum, and passing backwards is inserted into the stapes 

 by a tendon, in which I found a bone in the large bottle-nose. This muscle . 

 gives the stapes a lateral motion. What particular use in hearing may be pro- 

 duced by the action of these muscles, I will not pretend to say; but we must 

 suppose whatever motion is given to the bones must terminate in the movement 

 of the stapes. 



The immediate organ of hearing is contained in a round, bony process, and 

 consists of the cochlea and semicircular canals, which somewhat resemble the 

 quadruped; but, besides the 2 spiral turns of the cochlea, there is a 3d, which 

 makes a ridge within that continued from the foramen rotundum, and follows 

 the turns of the canal. The cochlea is much larger, when compared with the 

 semicircular canals, than in the human species and quadruped. 



We may reckon 2 passages into the immediate organ of hearing, the foramen 

 rotundum, and foramen ovale. They are at a greater distance than in the quad- 

 ruped. The foramen rotundum is placed much more on the outer surface of 

 the bone, and not in the cavity of the bony tympanum ; but may be said to 



