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DISEASES OF THE BONES. 555
We do not possess trustworthy information in regard to the compo-
sition of bones at different ages. The analyses by E. Voit of bones of
dogs, and by Brubacher of bones of children, apparently indicate that
the skeleton becomes poorer in water and richer in ash with increase
in age. Graffenberger 1
has found in rabbits, 6£-7£ years old, that
the bones contained only 140-170 p. m. water, while the bones of the
full-grown rabbit 2-4 years old contained 200-240 p. m. The bones of
old rabbits contain more carbon dioxide and less calcium phosphate.
The composition of bones of animals of different species is but little known.
The bones of birds contain, as a rule, somewhat more water than those of mam-
malia, and the bones of fishes contain the largest quantity of water. The bones
of fishes and amphibians contain a greater amount of organic substance. The
bones of pachyderms and cetaceans contain a large proportion of calcium carbo-
nate; those of granivorous birds always contain silicic acid. The bone-ash of
amphibians and fishes contains sodium sulphate. The bones of fishes seem to
contain more soluble salts than the bones of other animals.
A great many experiments have been made to determine the exchange
of material in the bones—for instance, wr
ith food rich in l’me and with
food deficient in lime—but the results have always been doubtful or
contradictory. The attempts to substitute other alkaline earths or
alumina for the lime of the bones have also given conflicting results.2
On feeding sufficient calcium and phosphorus in the food Aron 3
found,
by strongly reducing the sodium and at the same time giving a large
amount of potassium, that the development of the bones was below
normal. On the administration of madder, the bones of the animal are
found to be colored red after a few days or weeks; but these experiments
have not led to any positive conclusion in regard to the growth or
metabolism in the bones.
Under pathological conditions, as in rachitis and softening of the
bones, an ossein has been found which does not give any typical gelatin
on boiling with water. This finding is still uncertain as otherwise path-
ological conditions seem to affect chiefly the quantitative composition
of the bones, and especially the relation between the organic and the inor-
ganic substance. In rachitis the bones are poorer in solids and these
are poorer in mineral substances than under normal conditions.
Attempts have been made to produce rachitis in animals by the use of
food deficient in lime. From experiments on fully developed animals
opposing results have been obtained. In young, undeveloped animals
1
Voit, Zeitschr. f. Biologie, 16; Brubacher, ibid., 27; Graffenberger in Maly’s
Jahresber., 21.
2
See H. Weiske, Zeitschr. f. Biologie, 31, and W. Stoeltzner, Pfliiger’a Arch., 122,
and H. Stoeltzner, Bioch. Zeitschr., 12.
1
Pfluger’a Arch., 106.
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