Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
head is in a very material degree supported ; 
posteriorly, the spinous processes of the dor¬ 
sal region become gradually shorter, and their 
extremities broad and flattened, so as gradu¬ 
ally to approximate in their shape those of 
the lumbar region. 
The vertebrœ of the loins are, in the Soli- 
peda, usually six in number : such is the case 
in the horse, zebra, and quagga; but in the 
ass there are but five lumbar vertebrae. This 
portion of the vertebral column is, in the 
class under consideration, possessed of great 
strength ; the bodies of the vertebrae are 
broad and firmly bound together ; the trans¬ 
verse processes of remarkable length and 
power ; the articulating apophyses strong and 
broadly connected with each other, while the 
spinous processes, which are of great breadth, 
are either quite straight or inclined forward. 
The sacrum in all the Solipeda is composed 
of five vertebrae consolidated into one piece, 
and, with that exception, scarcely different 
from the vertebral pieces that immediately 
precede and follow it. In the horse, as in 
most quadrupeds, the sacrum is much nar¬ 
rower in proportion than in the human sub¬ 
ject, and forming, moreover, a continuous 
straight line with the rest of the spinal column, 
allows of much more freedom of motion in 
this part of the skeleton than is possible in 
the human subject; and this is much increased 
by the obliquity of the junction between the 
sacrum and the iliac bones. The articulation, 
moreover, between the last lumbar vertebra 
and the sacrum, still further adds to the 
mobility of these parts ; for in the horse, the 
oblique processes of that vertebra are con¬ 
nected with the sacrum by means of articu¬ 
lating surfaces of very large size, so that from 
the combination of all these circumstances, 
there is a springiness given to this region of 
the vertebral column, the importance of which, 
in galloping or leaping, is at once conspicuous. 
The caudal vertebrœ in the solipeds vary 
in number from seventeen to twenty-one ; but 
of these, the upper ones only resemble true 
vertebrae. Even in the first caudal vertebra, 
the inferior oblique processes become ob¬ 
literated, and as we descend, all the vertebral 
apophyses rapidly disappear : at the second 
bone of the tail, the spinal laminæ no longer 
rise high enough to enclose the spinal canal ; 
but resemble two short processes; and at 
about the fifth or sixth, all vestiges of them 
are lost, nothing remaining but the bodies of 
the vertebrae of a cylindrical shape and slightly 
enlarged at each extremity, until we approach 
the last, where all regularity of form is lost. 
Thorax. — The sternum of the solipeds is 
considerably compressed towards its anterior 
extremity, which is moreover prolonged to 
some extent beyond the insertion of the first 
rib, so as to give to the whole chest a cari- 
nated appearance, which forcibly reminds the 
anatomist of the thorax of a bird. Posteriorly, 
the carinated form disappears, and the sternum 
becomes broad and flattened where it receives 
the cartilages of the posterior true ribs. The 
sternum of the horse is composed of several 
osseous pieces bound together by strong liga¬ 
mentous and cartilaginous connections. 
The ribs are eighteen in number, so that 
the thorax is prolonged very far backwards 
towards the pelvis. The anterior ribs are 
broad and massive ; but of these, eight only 
are attached to the sternum : the posterior or 
false ribs gradually become more slender as 
they recede backwards to expand over the 
cavity of the abdomen. 
Anterior extremity.—The frame-work of the 
shoulder in the Solipeda, as in all ungulate 
quadrupeds, is composed of the scapula only ; 
the coracoid apparatus being dubiously repre¬ 
sented by a rudimentary apophysis, and the 
clavicle is totally wanting in circumstances 
which allow of the close approximation of the 
shoulder blades to the sides of the chest, and 
thus cause the weight of the body to be trans¬ 
mitted perpendicularly to the ground. 
The shape of the scapula {fig. 498. o) is al¬ 
most that of an isosceles triangle, the spinal 
costa, which is about half the length of the 
other two, having its angles rounded off. 
The spine of the scapula is prominently deve¬ 
loped, and towards its upper third, projects 
posteriorly, so as to form a considerable re¬ 
curved process (i) ; as it approaches the neck 
of the bone, however, the scapular spine be¬ 
comes quite obliterated, spreading out upon 
the margin of the glenoid cavity (A), so that 
no acromion process exists in these quadru¬ 
The humerus (fig. 498. e, b,k) is short, but 
of great strength, and the muscular imprints 
strongly marked. 
The forearm is almost exclusively formed by 
the radius (fig. 498. o,r), the strength of which 
is in accordance with the enormous weight it 
has to sustain, while the ulna is reduced to a 
mere appendage (figA98.s,t, u), which in the 
adult animal is completely consolidated with 
its posterior surface, the line of demarcation 
between the two being only indicated by a fur¬ 
row which, towards the upper extremity of 
the forearm, deepens into a slight fissure* 
The olecranon process is, however, of large 
size, and, by its projection posteriorly, affords 
a powerful purchase to the massive extensor 
muscles inserted into this portion of the limb. 
From the above arrangement of the bones of 
the forearm, it is manifest that all movements 
of pronation and supination are here out of 
the question ; the limb must remain constantly 
fixed in a state of pronation, in which con¬ 
dition it is anchylosed, and thus acquires a 
firmness and steadiness which would be quite 
incompatible with more extensive movements. 
The carpus in the Solipeda consists of seven 
bones arranged in two rows, — of which four 
are situated in the first, and three in the 
The upper series consists of the representa¬ 
tive of the os scaphoides of the human subject 
(fig. 498. w) ; of the os lunare (a?) ; of the 
cunéiforme (?/) ; and of the os pisiforme (z). 
In the lower series, the os trapezium, which 
supports the thumb of the human hand, does 
not exist in the horse ; but the trapezoid (not


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