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HYALOGENS. 171
salts; it is also precipitated by several metallic salts. If mucin is heated
on the water-bath with dilute hydrochloric acid of about 2 per cent,
the liquid gradually becomes a yellowish or dark brown, and reduces
copper salts in alkaline solutions.
The mucin most readily obtained in large quantities is the submax-
illary mucin, which may be prepared in the following way: The filtered
watery extract of the gland, free from form-elements and as colorless
as possible, is treated with 25 per cent hydrochloric acid, so that the
liquid contains 1.5 p. m. HC1. On the addition of the acid the mucin
is immediately precipitated, but dissolves on stirring. If this acid liquid
is immediately diluted with 2-3 vols, of water, the mucin separates and
may be purified by redissolving in 1-5 p. m. acid, and diluting with
water and washing therewith. The mucin of the navel-cord may be
prepared in the same way. As a rule the mucins can be prepared by
precipitation with acetic acid and repeated solution in dilute lime-water
or alkali, and reprecipitation with acetic acid. Finally they are treated
with alcohol and ether. In the preparation of sputum mucin the method
is very complicated (Fr. Muller).
Mucoids or Mucinoids. In this group we must include those non-
phosphorized glycoproteins which are neither true mucins nor chondro-
proteids, although they show among themselves such differences in
behavior that they can be divided into several subgroups of mucoids.
To the mucoids belong pseudomucin, the probably related body colloid,
ovomucoid, and other bodies, which on account cf their differences will be
best treated individually in their respective chapters.
Hyalogens. Under this name Krukenberg l
has designated a number of
different bodies, which are characterized by the following: By the action of
alkalies they change, with the splitting off of sulphur and some nitrogen, into
soluble nitrogcnized products called by him hyalines, and which yield a pure car-
bohydrate by further decomposition. We find that very heterogeneous sub-
stances are included in this group. Certain of these hyalogens seem undoubtedly
to be glycoproteins. Neossin 2
of the Chinese edible swallow’s-nest, membranin*
of Descemet’s membrane and of the capsule of the crystalline lens, and spiro-
graphin 4
of the skeletal tissue of the worm Spirographs, seem to act as such.
Others, on the contrary, such as hyalin 5
of the walls of hydatid cysts, and arm-
phin* from the tubes of Onuphis tubicola, do not seem to be compound proteins.
The so-called mucin of the holothuria, 7
and chondrosin 8
of the sponge, Chondrosia
1
Verh. d. physik.-med. Gesellsch. zu Wurzburg, 1883; also Zeitschr. f. Biologie, 22.
2
Krukenberg, Zeitschr. f. Biologie, 22.
3
C. Th. Morner, Zeitschr. f. physiol. Chem., 18.
4
Krukenbere, Wurzburg, Verhandl., 1883: also Zeitschr. f. Biologie, 22.
5
A. Lucke, Virchow’s Arch., 19; also Krukenberg, Vergleichende physiol. Stud.,
Series 1 and 2, 1881.
6
Schmiedeberg, Mitth. aus d. zool. Stat, zu Neapel, 3, 1882.
7
Hilger. Pfliiger’s Archiv, 3.
8 Krukenberg, Zeitschr. f. Biologie, 22.
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