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554 TISSUES OF THE CONNECTIVE SUBSTANCE.
Bone Marrow. We differentiate between the red and yellow mar-
row, to which also belongs the gelatinous marrow, poor in fat, found in
fat atrophy and in old age. The difference between the first two-men-
tioned kinds of marrow lies, essentially, in the fact that the red marrow
contains a greater quantity of erythrocytes besides a higher content of
protein and less fat. The fat of the yellow marrow is, according to
Xerring,1
richer in oleic acid and poorer in solid fats than the fat of the
red marrow. Besides the fat, lecithin also occurs in the bone-marrow
and this varies in amount in different animals and at various ages, as
mentioned on page 244. The protein consists of a globulin coagulating
at 47-50° C. (Forrest) and a nucleoprotein with 1.6 per cent phos-
phorus (Halliburton 2
) besides fibrinogen (P. Muller 3
), traces of
albumin and proteose. In the extractives are found lactic acid, inosite,
hypoxanthine, cholesterine and bodies of an unknown kind. The quan-
titative composition of both kinds of marrow varies considerably with
the fat content, and the reports of the different investigators are corre-
spondingly discrepant (Xerking, Hutchinson and Macleod 4
)
.
The diverse quantitative composition of the various bones of the
skeleton depends probably on the varying quantities of other tissues,
such as marrow, blood-vessels, etc., which they contain. The same
reason explains, to all appearances, the larger quantity of organic
substance in the spongy part of the bones as compared with the more
compact parts. Schrodt 5
has made comparative analyses of different
parts of the skeleton of the same animal (dog) and has found an essen-
tial difference. The quantity of water in the fresh bones varies between
138 and 443 p. m. The bones of the extremities and the skull contain
138-222, the vertebrae 168-443, and the ribs 324-356 p. m. water. The
quantity of fat varies between 13 and 269 p. m. The largest amount
of fat, 256-269 p. m., is found in the long tubular bones, while only
13-175 p. m. fat is found in the small short bones. The quantity of
organic substance, calculated from fresh bones, was 150-300 p. m., and
the quantity of mineral substances 290-563 p. m. Contrary to the
general supposition the greatest amount of bone-earths was not found
in the femur, but in the first three cervical vertebrae. In birds the
tubular bones are richer in mineral substances than the flat bones
(During), and the greatest quantity of mineral bodies has been found
in the humerus (Hiller, During 6
).
1
Bioch. Zeitschr., 10.
2
Forrest, Journ. of Physiol., 17; Halliburton, ibid., 18.
’See footnote 1, p. 253.
4
Nerking, 1. c; Hutchinflon and Macleod, Journ. of Anat. and Physiol., 36.
’Cited from Maly’s Jahresber., 6.
6
Hiller, eited from Maly’s Jahresber., 14; During, Zeitschr. f. physiol. Chem., 23.
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