Volltext: The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins (2)

whose long axis is vertical, it is articulated 
with the anterior and internal part of the navi¬ 
cular bone, and in front a large and irregular, 
slightly concave articular facet adapts it to the 
posterior extremity of the metatarsal bone of 
the great toe. Its inner surface is convex and 
rough for ligamentous insertion ; on it, towards 
its anterior part, we observe an impression, 
sometimes an eminence, for the insertion of 
the tibialis anticus tendon ; and its plantar 
surface, the base of the wedge, is thick and 
prominent, and affords insertion to ligamentous 
fibres as well as to those of the tibialis posticus 
tendon. The external surface is articulated in 
front with the second metatarsal bone, and 
behind with the middle cuneiform, by means 
of an oblong articular facet, which extends 
along the upper part of this surface from before 
backwards parallel to the acute edge. The 
remainder of the external surface is rough for 
ligamentous insertion, excepting a small por¬ 
tion about the sixth of an inch broad, which, 
extending along the posterior edge, is articular 
and continuous with the posterior surface of 
the bone. 
The middle or second cuneiform bone is the 
smallest of the three ; its base is uppermost, 
rough and convex ; its posterior surface is tri¬ 
angular with the base superior ; it is articular 
and adapted to the middle facet on the anterior 
surface of the navicular; its anterior surface is 
also triangular and articulated with the second 
metatarsal bone ; its inner surface is articular 
along its upper and posterior edges, and rough 
in the remainder of its extent; this surface is 
in contact with the inner cuneiform. The outer 
surface is articular along half of its upper edge 
and the whole of its posterior, but rough in 
the remainder, and by means of the articular 
portions is connected with the external cunei¬ 
form bone. 
The external or third cuneiform bone is 
second in point of size ; it is bounded on the 
outside by the cuboid, behind by the navicular, 
on the inside by the middle cuneiform, and in 
front by the third metatarsal bone. Its pos¬ 
terior and anterior surfaces are both plane and 
articular, the one for the navicular, the other 
for the third metatarsal bone. The base of the 
wedge is situated on the dorsal surface of the 
foot, and is rough. The internal surface 
presents at its posterior edge a facet for arti¬ 
culation with the middle cuneiform, and in 
front another for the second metatarsal ; the re¬ 
mainder is non-articular. The external surface 
presents, towards its upper and posterior angle, 
a plane triangular facet, which is adapted to a 
similar one on the inner surface of the cuboid, 
but in the rest of its extent it is rough and non- 
Structure of the tarsal hones.—Like all the 
short bones, those of the tarsus are composed 
of a mass of spongy tissue surrounded by a 
thin and papyraceous layer of compact. Hence 
these bones are remarkable for their extreme 
Developement. — In the third month the 
cartilaginous framework of these bones is 
already apparent. The largest two begin to 
ossify before birth ; the os calcis commences at 
from the fifth to the seventh month, by a single 
point of ossification situate about the middle of 
the bone rather nearer to its anterior part, and the 
ossification is not completed till eight or ten years 
after birth, when another point appears in the 
posterior part of the bone, and by the extension 
of it to the first point, which is finished about 
the fifteenth year, the process is completed. 
The ossification of the astragalus commences 
about the sixth month. The cuboid and navi¬ 
cular begin to ossify immediately after birth 
by one point each, and the three cuneiform 
bones are ossified, the internal about the end 
of the first year, the middle and external about 
the fourth year. 
II. Metatarsus ( der Mittel/uss).—This seg¬ 
ment of the foot is composed of five bones 
placed parallel to each other in front of the 
tarsus, with which their posterior extremities 
are articulated. These bones are distinguished 
numerically, counting from within outwards ; 
a distinct interosseous space intervenes between 
each pair of bones, which in the recent state is 
filled by muscle. From the arched form of 
the tarsus, the metatarsus naturally takes a 
similar arrangement by reason of its articula¬ 
tion with it, and consequently we observe that 
it is convex on its dorsal surface and concave 
on its plantar. 
The metatarsal bones possess certain general 
characters in common ; they belong to the class 
of long bones, and consequently each has its 
shaft and two extremities. The shaft in all is 
prismatic, slightly curved, convex on the dor¬ 
sal, concave on the plantar surface ; two of the 
surfaces of the shaft are lateral, and correspond 
to interosseous spaces ; the third is superior, 
and corresponds to the dorsum of the foot. 
The posterior or tarsal extremity of each 
metatarsal bone is wedge-shaped, the base of 
the wedge being on the dorsal aspect. Three 
articular facets may be noticed on each, ex¬ 
cepting the first and fifth. The posterior of 
these is triangular and plane, articulated with 
the tarsal bones ; the remaining two are lateral, 
and adapted to corresponding ones on the 
metatarsal bones on each side. 
The anterior or digital extremity of each 
metatarsal bone presents an articular head or 
condyle, flattened upon the sides, oblong from 
above downwards, and much more extended 
inferiorly or in the direction of flexion than 
superiorly or in that of extension. This is 
articulated with the posterior extremity of the 
metatarsal phalanx. On each side of the con¬ 
dyle there is a depression, and behind that 
an eminence to which the lateral ligament of 
the metatarso-phalangeal joint is attached. 
In addition to the characters above men¬ 
tioned, there are certain special characters 
belonging to particular metatarsal bones which 
enable us to distinguish them from each 
The first, or metatarsal of the great toe, is 
distinguished, 1. by its considerable size and 
its being the shortest of the five bones; 2. its 
tarsal extremity is semilunar and concave, and 
has no lateral articular facet; 3. its digital


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