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TUNICIN. CHITIN. 839
tunicata, and the widely diffused chitin, found in the cuticle-formation of
invertebrates, arc of interest.
Tunicin. Cellulose seems, from the investigations of Amukonn, to occur
rather extensively in the animal kingdom in the aithropoda and the mollusks.
It has been known for a long time as the mantle of the tunicata, and this animal
cellulose was called tunicin by Berthelot. According to the investigations
of Winterstein there does not seem to exist any marked difference between
tunicin and ordinary vegetable cellulose. On boiling with dilute acid, tunicin
yields glucose, as shown first by Franchimont and later confirmed by Win-
terstein. By the action of acetic acid anhydride and sulphuric acid, upon
tunicate-cellulose, Abderhalden and Zemplen 1
obtained octoacetyl-cellobiose,
which also indicates the relationship with the plant cellulose.
Chitin is not found in vertebrates. In invertebrates chitin is alleged
to occur in several classes of animals; it occurs chiefly in cephalopods
(sepia scales) and especially in the arthropods, in which it forms the
chief organic constituent of the shells, etc. It has been found in the
plant kingdom as in fungi (Gilson, Winterstein 2
). The question
whether there are two or more chitins or whether there is only one
is still disputed (Krawkow, Zander, Wester 3
). No formula can be
given for the same reasons (Sundwik, Araki, Brach 4
).
Chitin is decomposed on boiling with mineral acids and yields, as
shown by Ledderhose, glucosamine and acetic acid. Hoppe-Seyler
and Araki found, on heating with alkali and a little water to 180°, that
chitin was split into a new substance, chitosan, and acetic acid, and that
this chitosan contained acetyl groups as well as glucosamine. Frankel
and Kelly as well as Offer 5
have obtained acetylglucosamine,
(C6Hi2N05)COCH3 and acetyldiglucosamine (Ci2H23N2 Cq)COCH3 as
cleavage products of chitin, and they consider chitin as a polymeric
monacetyldiglucosamine.
The chitosan which v. Furth and Russo 6
have obtained as a crys-
talline hydrochloric acid combination and which E. Loewy has obtained
as a crystalline sulphate is, according to the latter, a polymeric monacetyl-
diglucosamine with at least two monacetyldiglucosamine groups. Accord-
1
Ambronn, Maly’s Jahresber., 20; Berthelot, Annal. de Chim. et Phys., 56, Compt.
Rend., 47; Winterstein, Zeitschr. f. physiol. Chem., 18; Franchimont, Ber. d. deutsch.
chem. Gesellsch., 12; Abderhalden and Zemplen, Zeitschr. f. physiol. Chem., 72.
2
Gilson, Compt. Rend., 120; Winterstein, Ber. d. d. chem. Gesellsch., 27 and 28.
’Krawkow, Zeitschr. f. Biol., 29; Zander, Pfliiger’s Arch., 66; Wester, Chem.
Centralbl., 1909, II.
4
Sundwik, Zeitschr. f. physiol. Chem., 5; Araki, ibid., 20; Brach, Bioch. Zeitschr.,
38.
5
Ledderhose, Zeitschr. f. physiol. Chem., 2 and 4; Araki, 1. c, Frankel and Kelly,
Monatshefte f. Chem., 23; Offer, Bioch. Zeitschr., 7.
fr
v. Furth and Russo, Hofmeister’s Beitrage, 8; Loewy, Bioch. Zeitschr., 23; Brach,
1. c.
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