SRELETINS. 75 
thai i here are a number of chitins, amine derivatives of different 
carbohydrates (dextrose, glycogen, dextrin, etc.) ; they give different 
colour reactions with iodine. 1 Ledderhose - was the first to show that 
the reducing substance obtained by the action of mineral acids in 
chitin is nol Bugar but glucosamine (see p. !)). The equation re- 
presenting its decomposition he gives as follows : — ■ 
21 \H: N/) ln + GH,0 = 4C G H 1 ,NO, + 3C 2 H 4 0, 
(chitin) (water) (glucosamine) (acetic mid, 
Glucosamine is an amido-derivative of glucose; it forms crystalline 
salts, of which the hydrochloride is readily prepared by boiling chitin 
with hydrochloric acid; this is Boluble in water, and is dextrorotatory 
(a) D =-f-70°-6. The base is prepared by the action of baryta on the 
sulphate. It is crystalline and not fermentable with yeast. 
Schmiedeberg ; 1< m >ks upon chitin as an acetyl derivate of glucosamine, 
and as he has also obtained the latter substance from the chondroitin- 
sulphuric acid of cartilage, he regards it as indicating a connection 
between the skeletal tissues of vertebrate and invertebrate animals. 
By heating chitin with ten times its weight of caustic alkali at 180°, 
Hoppe-Seyler and Araki 4 obtained a substance which possesses the 
original form of the pieces of chitin, but differs from chitin in being 
very soluble in dilute acids such as act-tic acid : from such solutions it is 
precipitable by alkalis. This substance is called chitosan, and its forma- 
tion from chitin is shown in the following equation : — 
C 18 H 30 N 2 O 1 2+2H 2 O=C 14 H ?6 K 2 O 1 0+2C 2 H 4 O 2 
(chitin)" (water) ;<>san) (acetic acid) 
Chitosan in dilute acetic acid is levorotatory : (a) D =-17°'7 to 17°"9. 
By heating it with acetic acid in sealed tubes to 135°, a substance 
very like chitin is regenerated ; it, however, contains three, whereas 
true chitin only contains two acetyl groups. 
By boiling with concentrated hydrochloric acid, chitosan yields 
hydrochloride of glucosamine, formic and acetic acids. 
Neurochitin. — In Crustacea, chitin has been said to take the place of neuro- 
keratin as a support to the nerve fibres. 5 
Conchiolin (C ,II,.X ,' > u ) forms the organic basis of the shells of mussels 
and snails. On decomposition it yields leucine, perhaps glycocine, hut no 
tyrosine or reducing substance. It does not give the xanthoproteic, Millon's, 
nor the Adamkiewicz reactions. The byssus of molluscs is similar. The 
cementing substance between the eggs of various molluscs contains a substance 
more like keratin. Cornein, from corals (C^H^NgOgg), diners from conchiolin 
by giving a red colour with Millon's test ; on decomposition it yields leucine 
and a crystalline material called cornicrystallin. 
Spongin, the organic basis of the common sponge, yields as decomposition 
products, leucine and glycocine (Stadeler), but no tyrosine. 6 It does not give 
the colour reactions just mentioned ; it resembles conchiolin by yielding 
1 E. Zander {Arch. f. d. cjes. Physiol, Bonn, 1897, Bd. lxvi. S. 545) also finds that 
chitin gives a colour with iodine very like that given hy glycogen. 
2 Ztsehr. f. physiol. Ohem., Strassburg, Bd. ii. S. 213 ; iv. S. 137. 
* Arch.f. exper. Path. u. Pharmakol., Leipzig, Bd. xxviii. 
4 Ber. d. deutsch. eh m. Gesellsch, Berlin, 1894, Bd. xxvii. S. 3329 ; 1895, Bd. xxviii. S. 
82 : Ztsehr. f. physiol. Chan., Strassburg, 1895, Bd. xx. S. 498. 
5 Griffiths, Compt. rend. Acad. d. sc, Paris, tome cxv. 
6 Zalocostas (ibid., tome cvii. p. 252), however, obtained tyrosine, butalanine, and 
glucalauine CAl^.D^). 
