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PROFESSORS T. W. BRIDGE AND A. C. HADDON 
respective contents, the saccuh and sinus endolymphaticus, eventuall}’- filling the 
two atrial cavities and bathing the inner surfaces of the spoon-shaped processes 
of the “ stapedes.” 
The Weberian Ossicles. — A series of moveabl}'’ interconnected ossicles which, 
morphologically, are modified portions of the three anterior vertebrae, serve to 
connect the membranous labyrinth with the air-bladder and thereby establish close 
physiological relations between the two structures. As we have already pointed 
out, the most anterior of these in Macrones fits into and completely closes the 
external atrial aperture of its side and is therefore in contact by its inner surface 
with the perilymph ; the most posterior of its ossicles has the hinder half 
imbedded in the dorsal wall of the anterior chamber of the air-bladder. Fig. 24 
shows the general relations of the ossicles to one another, and to the membranous 
labyrinth and air-bladder, and in figs. 3 to 5 they are represented as they appear 
in situ.'"'' 
In Macrones each claustrum (figs. 4, 5 and 10, c.) is imbedded in the fibrous 
wall of the neural canal between the arch of the third vertebra and the exoccipital, 
and lies at the side of the foramen magnum, immediately behind, and almost 
in contact with, the posterior edge of the neural plate of the exoccipital. It is a 
slender spicular bone, slightly curved at its lower extremity where it is received 
into the angle between the ascending and spatulate processes of the scaphiura, 
and separated by the somewhat contracted root of the latter process from the body 
of the first vertebra (figs. 4 and 5, c.). The upper extremity of the ossicle is in 
contact with, and may even extend into, the intercalated cartilage between the spine 
of the third vertebra and the supraoccipital, while the inferior incurved extremity 
coincides with tlie level of the posterior margin of the roof of the cavum sinus imparis 
and extends into and helps to strengthen the roof of the atrial cavity of its side. 
Although in close contiguity with the scaphium by its lower extremity, the claustrum 
is not specially attached to it, nor does it appear that the claustrum can in any way 
control or influence the movements of the scaphium. 
The scaphium (figs. 10 and 11, also figs. 4 and 5, i>c.) lies just behind the 
claustrum, and consists of two processes united at a right angle, an ascending process 
(figs. 10 and 11 , sc.a.) and a horizontal or spatulate process (sc.s.). The former is 
imbedded in the fibrous wall of the neural canal behind and parallel to the claustrum 
(figs. 4 and 5, sc.a.), and consists of a slender spicule of bone with a slight forward 
curvature and a pointed upper extremity ; the latter, which has its origin from the 
inferior extremity of the ascending process by a somewhat contracted root, passes 
* For reasons already given (.5), we have suggested that the names applied to three of these ossicles, 
by Webek, viz., “malleus,” “incus,” and “stape.s,” may, with advantage, be replaced by “tripus,” 
“ intercalarium,” and “ scaphium,” respectively, retaining, however, the term “ claustrum ” for the 
fourth ossicle, while for the ossicles collectively, we suggested the name “Weberian” in preference to 
“ auditory.” 
