ANATOMY. 
stance, which is dissolved in the water. The 
earth of bones is demonstrated by calcina- 
tion, which drives off the animal matter, and 
leaves the earth alone behind. This earth 
consists chiefly of phosphate of lime ; but 
there is also a small proportion of carbonate 
of lime. In young subjects the animal sub- 
stance predominates ; and the bone appears 
redder, in consequence of the arteries being 
larger and more numerous. The bones of 
old persons contain more earth, and are con- 
sequently whiter and less vascular. 
Some recent experiments have shewn the 
quantity of jelly contained in bones to be 
much larger than was supposed, and as it 
forms a very good soup when dissolved in 
water, the circumstance is of considerable 
importance* as furnishing an article capable 
of supplying much wholesome nutriment; 
The quantity of soup furnished from a given 
bulk of bruised or pounded bones, boiled in 
a vessel with a closed lid, considerably ex- 
ceeds that which can be extracted from the 
same quantity of meat. Of course the arti- 
cular heads of bones, and the reticular tex- 
ture, in general furnish the greatest quan- 
tity. 
It has been generally taught, that bones 
are composed of fibres and laminae : the 
fact is that they consist of a reticulated tex- 
ture, very similar to cellular substance in 
other parts of the body. 
According to the obvious differences in 
their forms, bones are divided into the long 
and flat. 
Two kinds of structure may be observed 
in all bones : in the one* the bony substance 
is condensed* and leaves no interstices ; in 
the other, there is a mere net-work of bony 
fibres and plates, leaving numerous inter- 
vals. The latter is termed the cancellous 
substance of bones. 
The cylinder of a long bone is composed 
entirely of the firmer substance, and in its 
centre is hollowed out to contain the mar- 
row. In those extremities of the bones, 
which form the joints* which are greatly ex- 
panded, in order to increase the extent of 
surface, there is a thin layer of the compact 
substance, but all the interior is cancellous; 
In broad or flat bones, the firmer substance 
is formed into two plates or tables, and the 
interval between these is occupied by can- 
celli. 
Many advantaged arise from this arrange- 
ment of the earth of bones. The long bones 
are made slender in the middle, to allow of 
the convenient collocation of the large mus- 
cles around them ; they become expanded 
VOL; I, 
at their extremities, to afford an extent of 
surface for the formation of joints, and the 
support of the weight of the body. A ca- 
vity is left in the middle ; for if all the 
earthy matter had been compacted into the 
smallest possible space, the bones would 
have been such slender stems, as to be very 
unsuitable to their olfices ; and if they had 
been of their present dimensions, and solid 
throughout, they would have been unneces- 
sarily strong and weighty. 
The phenomena, which result from feed- 
ing an animal with madder, sufficiently de- 
monstrate the existence of blood-vpssels 
and absorbents in the bones; There is a 
strong attraction between the earth of bone 
and the colouring matter; by means of 
which they unite and form a beautiful red 
substance. The whole of the bones of an 
animal assume this colour soon after an ani- 
mal has been taking the madder. If it be 
left off, the bones in a short time resume 
their natural white appearance, from the ab- 
sorption of the red colouring substance. 
The short time in which growing bones be- 
come thorohghly died, and in which again 
the preternatural tint is lost* prbve that 
even in these, the hardest parts of bur 
frames, there is a process of removal of bid 
parts, and deposition of nfew ones constantly 
going on. 
That bones possess nerves, as well as ar- 
teries, veins, and absorbents, cannot be 
doubted. Although in the natural state they 
seem to be insensible, they become ex- 
tremely painful When diseased ; and again, 
a fungus which is sensible sometimes grows 
out of a bone, though it may have no con- 
nexion whatever with the surrounding soft 
parts ; of course it must have derived its 
nerves, by means of which it possesses sen- 
sation, from the bone out of which it arose. 
Bones are covered by a strong and firm 
membrane, termed periosteum, on which the 
vessels are. first distributed ; from this they 
descend into the substance of the bone. 
The vessels enter through holes, which are 
evident on the surface, and which are larger 
and more numerous in the extremities of 
tire long bones than in the middle; 
OF THE MARROW. 
This is of an oily nature. It hardens, 
When Cold* in herbaceous animals ; but it 
remains fluid in those which are carnivo- 
rous. It has a reddish and bloody appear- 
ance in young animals ; but this soon goes 
off. It is contained in fine membranous 
cells, which do not communicate with each. 
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