1 6 CHEMICAL CONSTITUENTS OE BODY AND FOOD. 
Bernard originally taught), or is employed in the synthesis of fat and proteid 
(as Pavy holds). 
Dextrin is the name given to a number of intermediate substances 
formed during the hydrolysis of starch ; the principal varieties are 
erythrodextrin, which gives a red colour with iodine; achroddextrin, which 
does not ; and maltodextrin, which has a lower molecular weight than 
these. 1 The dextrins are dextrorotatory (maltodextrin has an (a) D = + 
174 0, 5). They are soluble in water, and insoluble in alcohol and ether. 
They give a blue solution with Trommel's test, but no reduction occurs 
on boiling. 
Animal gum was discovered by Landwehr, 2 and resembles achroodextrin 
and glycogen in some of its properties. It is a decomposition product of 
mucin. When boiled with dilute sulphuric acid it yields a reducing but 
unfermentable sugar. Animal gum, like the vegetable gums, gives gelatinous 
precipitates with copper and iron salts. 
Animal dextran is a gummy material, secreted by the Schizoneura 
lanuginosa, a gall-producing louse that attacks elms. 3 
Vegetable gums and mucilages include such substances as gum arable, 
wood gum, etc., which are of subordinate physiological interest. 
Cellulose is the name given to a number of carbohydrates which form 
the chief constituent of vegetable cell walls. In old cells, where it 
becomes very insoluble, it is called lignin, The celluloses are insoluble 
in cold and hot water, in alcohol, ether, and dilute acids and alkalies. 
A specific reagent for dissolving them is Schweitzer's reagent (a solution 
of cupric hydrate in ammonia). 
With iodine and concentrated sulphuric acid they are turned blue ; 
with nitric acid they yield nitroso-compounds of an explosive nature 
Prolonged treatment with strong mineral acids leads to the formation of 
sugars ; in some cases glucose, in others mannose, is formed. Schulze's 
mannoso-cellulose, 4 found in coffee and other seeds, is not a hemicellu- 
lose (see next paragraph). The celluloses are not acted upon by the 
digestive ferments proper; but they may be broken up in the intestine 
by bacteria into carbonic acid and methane. 
Hemicelluloses are those varieties of cellulose which differ from the others 
by yielding monosaccharides by treatment with dilute mineral acids. The 
hemicellulose of yellow lupins yields galactose and arabinose ; that of rye and 
wheat, arabinose and xylose ; that of certain nuts, mannose. 
Tunicin is animal cellulose. It is the chief constituent of the test or outer 
investment of the tunicates. 
Cellulose has also been found in the animal kingdom in the skin of the 
silkworm, 7 and in the zoocytium of Ophrydium rersettile. 8 
Inosite. — Inosite is a substance found in muscle and other animal 
tissues, and in many vegetables also. Its crystalline form is shown 
1 Recent papers on dextrin will be found in Ber. d. deutsch. chem. Gesellsch., Berlin. 
Bde. xxiii. S. 3060 ; xxvi. S. 2930 (by Scheibler and Mittelmeier), and Bd. xxvi. S. 
2533 (by Leubner and Doll). 
- Ztschr.f. physiol. Chem., Strassburg, Bd. viii. S. 119, 124. 
3 Liebermann, Arch. f. d. ges. Physiol., Bonn, Bd. xl. S. 454. 
4 Ztsehr. f. physiol. Chem., Strassburg, Bd. xvi. 
5 See Scbulze, loc. cit. ; and Reiss, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxii. 
6 Schiifer, Ann. d. Chem., Leipzig, Bd. ccx. S. 312; Berthelot, Ann. deehim., Paris, 
Se>. 3, tome lvi. p. 153. 
7 De Lucca, Compt. rend. Acad. d. sc, Paris, tome lii. p. 102 ; lvii. p. 43. 
s Halliburton, Quart. Joum. Micr. Sc, London, July 1885. 
