Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Todd, Robert Bentley
at least in the remains lately described by Mr. 
Elift, the part joining the sternum, and answer¬ 
ing to the cartilages of the ribs, is bony and is 
connected to the rib itself by a moveable arti¬ 
culation. The lumbar vertebra are generally 
broad and furnished with strong spinous pro¬ 
cesses. The transverse processes are incon¬ 
siderable in the Sloths, but large in the Edentata 
proper. In the Armadillos the anterior articu¬ 
lar processes are particularly strong and larger 
even than the spinous. This is the case, but to 
a less degree, in the Ant-eaters. In the Orycte- 
ropus there are slight indications of inferior 
spinous processes on most of the lumbar verte¬ 
brae, consisting of a small longitudinal crest. 
The caudal vertebra vary excessively in num¬ 
ber. In the Unau and Bradypus didactylus 
they are very few—not more than seven or 
eight ; in the large Ant-eater forty, and in the 
African Manis forty-five. In the remains of 
the Megatherium lately deposited in the Mu¬ 
seum of the Royal College of Surgeons, the 
tail would appear, according to Mr. Clift’s 
computation, to consist of eighteen vertebrae at 
least. The caudal vertebrae of the Edentata 
proper have inferior spinous processes of a 
remarkable form, being constituted of two 
branches meeting inferiorly in the median line. 
The Megatherium possesses similar V-shaped 
processes. In the Myrmecophaga didactyla the 
two branches are not united in the anterior two 
of them. The sternum offers a considerable 
developement of themanubriumor anterior bone 
in the whole of the Edentata, particularly in the 
Ant-eaters and Armadillos. It is also rather 
large in the Megatherium. 
The pelvis in the Edentata proper is much 
elongated, and the acetabulum rather behind the 
middle of the whole length of the bones. The 
ileum, which forms the anterior half of the pel¬ 
vis in the Armadillo, is fixed to the sacrum by 
its posterior portion, a surface of considerable 
extent. The ischium and pubis are large, the is- 
chiatic notch wide, and the cavity of the pelvis 
capacious. In the Sloths and Megatherium 
the pelvis is of large dimensions, the ilia very 
broad, especially in the latter; the cavity capa¬ 
cious, and the outlet large. The ossa pubis are 
joined at the symphysis in most of the Eden¬ 
tata, as is now ascertained by Mr. Clift, in the 
Megatherium. In the Myrmecophaga didac¬ 
tyla, it is stated by Cuvier to be open. The size 
of the pelvis in the Megatherium is enormous. 
On comparison of it with the pelvis of an 
elephant eleven feet in length, Mr. Clift found 
that in the former the ilia are 5ft. lin , and in 
the latter only 3ft. 8in. 
The anterior extremity.—The principal cha¬ 
racteristic of the bones of the arm in the Sloth 
is their extraordinary length. The humerus is 
very much elongated and cylindrical, with the 
elevations but slightly marked. The ulna and 
radius are also very long, and bowed, so that 
the bones are distant at the middle of their 
length ; the radius is very broad anteriorly. 
The very complete power of pronation and su¬ 
pination enjoyed by this animal is no less ob¬ 
viously suited to its habits than the great 
length of its anterior extremities ; both of which 
peculiarities arc admirably subservient to the 
complicated objects of holding by the boughs, 
of advancing along their under-surface, and of 
reaching and bringing to the mouth the leaves 
on which it feeds ; and the structure of the 
hand (fig. 35) is no less suited to the same pur- 
Fig. 35. 
Hand of the Sloth. 
poses. The carpus is as long as it is broad ; it is 
composed of six pieces only, of which four form 
the first series, and two the second. The os 
scaphoïdes is the largest of the whole, and is 
articulated with the os semilunare by a convex 
articular surface : the os cunéiforme presents on 
its ulnar side an oblique flattened surface ; the 
os pisiforme, which is not named by Cuvier, 
does however exist, though it is of small size. 
The inner and larger piece of the anterior series 
probably consists of the os trapezium, trape- 
zoideum, and magnum united; and the external 
one solely of the os une forme. In the Unau the 
os trapezdides is distinct. The metacarpal 
bones, to return to the Aï, consist of three per¬ 
fect and two rudimentary, the whole of which 
are united at their base to each other and to the 
inner solid carpal piece, consisting of the three 
bones before mentioned; so that in fact the five 
metacarpal bones, with the os trapezium, tra- 
pezoideum, and magnum, form one solid osseous 
piece. The fingers, which are three only, are 
very long, and consist each of two moveable 
phalanges only, the first being very small and 
early anchylosed to the metacarpal bone. In a 
very young skeleton in my possession, these 
bones are not yet united. There is but very 
little flexion between this part and the second 
phalanx, but between the latter and the third or 
ungueal phalanx the flexion is complete, the 
latter being bent down to the palm with perfect 
ease. These ungueal bones are very long, 
curved, laterally compressed, large at the base, 
at which part there is, as in the cats, a bony 
sheath to cover the base of the claw; and the 
latter envelopes the phalanx for about five-sixths 
of its length. 
The posterior extremity in this remarkable 
animal offers no less striking peculiarities. 
The breadth and openness of its pelvis have been 
already noticed. Thefemur is articulated to the 
acetabulum so as to stand obliquely outwards 
from the pelvis ; it has a short head, and is it¬ 
self rather short, strong, and flattened. The 
tibia and fibula are long and slender, and some¬ 
what curved ; the superior articular surfaces of 
the tibia are flat, that of the inferior extremity


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