Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
different genera, and even in different species. 
It generally consists of a body or centrum, 
which is sometimes itself divided into several 
pieces, and of two and sometimes three pairs 
of cornua ; also under the anterior part of its 
body there is suspended a bone or a cartilage 
(sometimes double) which is the special bone 
of the tongue, the analogue of the lingual 
bone of birds, only in them it is articu¬ 
lated in front of the body of the hyoid bone, 
whilst in the Chelonians it is suspended under¬ 
The greater cornua (the anterior pair, when 
only two pairs are present, the middle pair 
when there are three, that which represents 
the styloid bones) embrace the oesophagus, 
and ‘mount up behind those muscles which 
represent the digastric or depressors of the 
lower jaw, but without being attached other¬ 
wise than by their own muscles. 
In Trionyx, the body of the os hyoïdes, 
is composed anteriorly of a cartilaginous point, 
beneath which is suspended a large lingual 
cartilage of an oval form. At the base of 
each pointed cartilage there is attached an 
osseous piece of a rhomboidal shape, which 
represents the anterior cornua; behind this 
are four other pieces, forming a disc, which is 
concave superiorly, broadest in front, and 
deeply notched both posteriorly and on each 
side. To the anterior angles of this disc are 
appended the middle cornua and to the pos¬ 
terior the posterior cornua. All four of these 
cornua are considerably ossified. The middle 
cornua consist of one long piece, which is 
compressed, of an arched form, and termi¬ 
nated by a little cartilage. The other cornua 
are broader and flatter ; they are eked out 
by a cartilage, in the thickness of which are 
enclosed five or six osseous nuclei, all placed 
in a line with each other, each of a round or 
oval form, and quite hard and distinct, so 
that the os hyoides of this reptile seems to 
consist of twenty different osseous pieces, 
which apparently remain distinct through life. 
The hyoid apparatus of Chelys is equally 
remarkable. Its body is composed of a single 
long narrow piece, of a prismatic shape, hol¬ 
lowed above into a canal in which the trachea 
is lodged. Anteriorly, this central portion ex¬ 
pands in order to sustain two additional pieces 
on each side, four in all, without reckoning 
the centrum itself. The two middle ones 
unite in front, leaving a space between them¬ 
selves and the principal body, which is closed 
by a membrane upon which the larynx reposes. 
The two lateral pieces perhaps represent 
the anterior cornua ; it is at the dilatation 
that they form with the expanded portion of 
the centrum that the middle cornua are ar¬ 
ticulated : these are very strong and prismatic 
for the internal half of their course ; afterwards 
slender ; and they give attachment externally 
to an additional piece, which is distinct from 
the rest of the cornua. 
The posterior cornua are articulated to the 
posterior extremity of the prismatic portion 
of the centrum; they are long, slightly com¬ 
pressed, and curved. Under the anterior and 
dilated portion is suspended the lingual bone, 
which consists anteriorly of a semicircular 
cartilage, and behind of two crescent-shaped 
osseous pieces, the inner angle of which is 
prolonged into a kind of tail or pedicle that 
passes beneath the prismatic body of the 
hyoid bone. 
In the turtles, the body of the hyoid re¬ 
sembles an oblong shield, concave upon its 
upper surface for the sake of lodging the 
larynx and the commencement of the trachea ; 
pointed in front, where it forms part of the 
tongue, laying above the lingual bone. The 
anterior cornua are very small ; the great 
cornua are articulated to [the middle of its 
lateral margin, and have at their free termi¬ 
nations additional cartilaginous pieces. The 
posterior cornua are attached to the posterior 
The pelvis of lizards (ßg. 184.) is composed 
Fig. 184. 
Pelvis of Crocodile, 
a, ileum ; i, ischium ; c, pubis. 
of three bones, which, as in quadrupeds, assist 
in the construction of the colyloid cavity. The 
os ilii (a) occupies the upper half; its neck 
is broad and short, and its spinous portion, 
instead of running forwards, as in mammifers, 
or being rounded, as in the crocodile, is di¬ 
rected obliquely backwards, in the shape of a 
narrow band. 
Inferiorly, the pubis (b) and the ischium (c) 
are conjoined with their fellows of the 
opposite side along the mesial line ; but the 
pubis does not unite with the ischium, and 
consequently the two infra-pubic foramina 
are only separated from each other by a liga¬ 
The pelvis of the different genera of lizards 
are principally distinguished from each other 
by the symphysis of the pubic bones, which 
in the monitors is formed by the junction of 
two broad truncated surfaces; but in most 
other genera by a much less extensive union. 
The junction between the ossa ischii is always 
effected by a wide surface. 
The chameleon differs from all other lizards 
in having the ossa ilii straight, and directed 
almost perpendicularly upwards, to be at¬ 
tached to the spine. They are likewise re-


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