yUZ MR. A. FRASER ON THE DEVELOPMENT OF THE 
parts are or are not derived from or connected with the upper extremities of these two 
cartilages in any one class of the Yertehrata. This portion of my work refers only to 
the Mammalia, but I hope soon to complete my observations upon the remaining classes 
of the Yertehrata. 
Before passing to the description of my own work I shall give a brief summary of 
the various views that have been advanced respecting the origin of the ossicula 
auditus. 
HISTORICAL. 
Meckel (1) described the cartilage of the first post-oral arch as a mere process of 
the malleus, but did not further refer to the origin of the ossicula. Bathke and 
Yalentin (2) describe the ossicula as having their origin in two nodules of cartilage 
which made their appearance in the tympanic cavity; one, the earlier and larger of 
the two, formed the elements of the incus, malleus, and Meckel’s process; while the 
other, which appeared later, formed the stapes. 
Htjschke (3) describes the malleus as arising from, the cartilage of the first post¬ 
oral arch, the incus from the cartilage of the second, while the two cartilages united 
at their proximal extremities to form the stapes. 
Burdach (4), while accepting with some doubts the last-mentioned origin for the 
malleus and incus, thought the stapes ought to be considered as a bud from the wall 
of the labyrinth. 
Reichert (5) divides the first post-oral cartilage into three portions, the posterior 
of which connected the cartilage to the cranial vertebrae, and did not undergo any 
further change, but finally disappeared; the median division formed the incus with 
its processes; the anterior, the malleus, and Meckel’s process. 
The second post-oral cartilage was at first connected to the base of the cranium in the 
region of the post-sphenoid ; this part, however, soon disappeared, and the remainder 
of the cartilage formed in succession the stapes, stapedius muscle, eminentia pyra- 
midalis, styloid process, stylo-hyoid ligament (generally), and lesser cornu of the hyoid 
bone. 
Ghnther (6) while in the main accepting Reichert’s views respecting the cartilage 
of the first arch, considered his description of the second, so far as it referred to the 
stapes, to be untenable. He described the origin of the stapes as follows : from the 
median of the three divisions of the first post-oral cartilage a nodule arose which 
applied itself to the wall of the labyrinth; formed a depression there—the future 
fenestra ovalis; this nodule, by the growth of the parts, chiefly the cochlear part of 
the labyrinth, became more remote from its place of origin, and formed a process, which 
process becoming bent on itself, formed a horizontal part—the stapes, and a vertical 
part—the long crus of the incus ; this division formed also the incus with its processes. 
Malleus, incus, and stapes were thus derivatives of the first post-oral cartilage. 
Magitot et Robin (7) describe the malleus as arising from the intra-tympanic 
