1882.] Ossicula Auditus in the Higher Mammalia. 447 



He lias ascertained that the head of the incus is the proximal 

 extremity of the hyoidean cartilage, the long eras forming the con- 

 necting part between it and the remainder of the cartilage. The short 

 eras is a later growth backwards from the head of the incus. This 

 ossicle agrees in its histological characters with the hyoidean cartilage 

 and not with the mandibular. The mandibular branch of the seventh 

 nerve bears also the same relation to its long crus in the human 

 embryos as it bears to the hyoidean cartilage. 



The orbicular apophysis is shown to be a part of the long crus, 

 which turns inwards to accommodate itself to the stapes at right 

 angles to its former direction ; its constricted pedicle is not formed 

 until after birth. 



The cells of the embryonic stapes appear contemporaneously with 

 those forming the embryonic cartilage in the arches, or those forming 

 the periotic capsule ; they are arranged in a circular form round an 

 artery, which may either disappear very early, as in the human em- 

 bryo, or persist through life, as in the rat. In the former case it is called 

 arteria stapedialis, in the latter arteria stapedio-maxillaris. This 

 circular ring is at first of equal thickness all round, and is not even in 

 contact with the periotic capsule, but is more closely connected with the 

 hyoidean cartilage, although its cells cannot be described as con- 

 tinuous with the cells of that cartilage, their long axes having a 

 circular and not an antero-posterior direction. 



Owing chiefly to the growth of the cochlear part of the labyrinth, 

 the stapes applies itself to the wall of that cavity, forms a depression 

 there, the future fenestra ovalis ; the margins of its base and the 

 head are the last to develop. 



The articulation between the head of the stapes and the long crus 

 of the incus is formed at the same time as that between the malleus 

 and incus. The tubercle on its posterior crus bears the same relation 

 to the stapedius muscle as the processus muscularis of Hyrtl to 

 the tensor tympani. The stapedius muscle agrees in its develop- 

 ment with the tensor tympani, or any other muscle in the region of 

 the head, and the nucleus in its tendon, which has been described as 

 an inter-hyal, has no connexion with the hyoidean cartilage, in truth, 

 not being present at all in any of the embryos on which T have 

 worked ; so that when it is present it must be looked upon as a 

 development in a tendon similar to that which occurs in many other 

 muscles of the body. 



The author was anticipated by Salensky in the publication of the 

 discovery of the peculiar mode of origin of the stapes round an 

 artery; but his observation of this fact was made independently of 

 Salensky's, and before the appearance of that writer's memoir, and 

 he has been able both to correct and to add considerably to Salensky's 

 description of the development of this ossicle. 



