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THYMUS. 367
protein substance which has been generally called nucleohislone. By the
action of dilute hydrochloric acid upon nucleohistone it splits, according
to these investigators, into histone and leuconuclein. The leuconuclein
is a true nuclein; hence it is a nucleic-acid compound with protein which
is relatively poor in protein and rich in phosphorus. The more recent
investigations of Bang, Malengreau, Huiskamp and Gouban * upon
nucleohistone all show that this nucleoprotein is not a unit substance, but
a mixture of at least two bodies. The views of the investigators men-
tioned differ quite essentially from one another as to the nature of these
bodies, but this is partly due to the different methods used by them and
partly to the ready changeability of the substances in question.
Besides the real nucleohistone, B-nucleoalbumin of Malengreau,
Lilienfeld’s histone contains a second nucleoprotein which Bang and
Huiskamp call simple nucleoprotein, while Malengreau designates
it A-nucleoalbumin. This protein, which contains only about 1 per cent
phosphorus and which is possibly identical with the nucleoprotein found
by Lilienfeld in the thymus, yields a nuclein, but no free nucleic acid,
on cleavage. As a second cleavage product it yields, according to Mal-
engreau, the A-histone, which can be readily precipitated by magnesium
and ammonium sulphates from the ordinary B-histone of the thymus
gland. The occurrence of A-histone in the gland has been verified by
Bang, and according to Bang and Huiskamp the A-histone is not derived
from the nucleoprotein, as these investigators claim that it yields no his-
tone. According to Bang the nucleoprotein yields only an albuminate,
besides the nuclein, as cleavage products. According to Gouban we
have been dealing with three substances, namely a nucleoprotein which
does not yield any histone, and two nucleohistones, which correspond
to the nucleoalbumins A and B of Malengreau and form the mixture
of lime-nucleohistone of Huiskamp. They occur in this last mentioned
mixture in a somewhat modified form due to the method of preparation.
The true nucleohistone, which is much richer in phosphorus (the-
calcium salt containing, according to Bang, on an average 5.23 per cent
P), yields ordinary histone (or 2 histones) as one cleavage product and
free nucleic acid as the other. According to Bang, whose statements
on this point have been substantiated by Malengreau, it splits on saturat-
ing with NaCl into nucleic acid and histone without yielding any other
protein. On this account Bang does not consider this body as nucleo-
histone in the ordinary sense, i.e., not as a nucleoprotein, but as a histone
1
Lilienfeld, Zeitschr. f. physiol. Chem., 18; Kossel, ibid., 30 and 31; Bang., ibid.
30 and 31. See also Arch. f. Math, og Naturvidenskab, 25, Kristiania, 1902, and
Hofmeister’s Beitrage, 1 and 4; Malengreau, La Cellule, 17 and 19; Huiskamp, Zeit-
schr. f. physiol. Chem., 32, 34 and 39; Gouban, Bioch. Centralbl., 9, 803.
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