14 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 
and so on, until at last we get to 
(C 6 H 10 O 5 ) 4 + H 2 = (C 6 H 10 9 5 ) 2 + C 12 H 22 O n 
(dextrin) (dextrin) (maltose) 
and finally 
(C 6 H 10 O 5 ) 2 + H 2 = C 12 H 22 O n 
(dextrin) (maltose) 
The principal sub-groups of the polysaccharides are the starch 
group, the gum group, and the cellulose group. The starch group 
includes starch, inulin, lichenin, and glycogen. The gum group includes 
the dextrins, the plant gums and mucilages, and animal gum. The 
cellulose group includes cellulose, the hemicelluloses, and tunicin. 
Starch is one of the most widely distributed carbohydrates in the 
vegetable kingdom. It occurs in nature in granules, which consist of 
two principal substances, starch-granulose and starch-cellulose ; of these 
the former only is dissolved by the digestive juices. Erythrogranulose, 
which gives a red colour with iodine, is present in small quantities 
(Briicke). 
Starch is insoluble in cold water, in alcohol, and in ether. With 
hot water it swells, forming an opalescent solution or starch paste. 
This, if concentrated, gelatinises on cooling. On hydrolysis it forms 
first soluble starch (also called amylodextrin or amidulin), then other 
dextrins, and finally maltose and dextrose. 
The most characteristic reaction of starch is the blue compound it 
forms with iodine. 1 It does not give Trommer's test or Moore's 
test, nor does it ferment with yeast. The specific rotatory power 2 
of soluble starch for concentrations of 2*5 to 4*5 per cent, at 15°*5 C, 
(a) D =+202°. 
Inulin is found in the roots of many composites. It is usually 
prepared from dahlias. It is the only polysaccharide which can be 
obtained in a crystallised form, namely, as sphero-crystals which 
polarise light. It is readily soluble in warm water ; by cooling the 
solution it is precipitated. By hydrolysis its final product is levulose. 3 
Lichenin is a polysaccharide occurring in Iceland moss, and certain 
almie. It is insoluble in cold water, soluble in hot water, gives a yellow 
colour with iodine, is converted into glucose by hot dilute mineral acids, 
but is not affected by saliva or pancreatic juice. 4 
Glycogen. — This is a small but constant constituent of protoplasm, 
and of animal tissues generally. It is found in white blood corpuscles, 5 
and in pus, 6 occasionally in diabetic urine, 7 but is specially abundant in 
1 E. Zander finds that the iodine reaction given by polysaccharides and by chitin varies 
considerably with the solvent used (Arch. /. d. ges. Physiol., Bonn, 1897, Bd. lxvi. 
S. 545). 
'- 1 Brown, Morris, and Millar, loc. cit. 
3 Kulz, "Beitr. z. Path, des Diabetes." Marburg, 1894, S. 130. ; AVorm-Muller, Arch, 
f. d. gcs. Physiol., Bonn, 1884, Bd. xxxiv. S. 576 ; 1885, Bd. xxxvi. S. 172 ; F. Hofmeister, 
Arch. f. exper. Path. u. Pharmakol., Leipzig, 1889, Bd. xxv. S. 240. On " Inulin as a 
Precursor of Glycogen," see Miura, Ztschr. f. Biol., Miinchen, Bd. xxxii. ; he obtained 
very inconstant results. 
4 Nilson, Upsala Lakarcf. Porh., vol. xxviii., quoted by Hammarsten, in "Physiol. 
Chem.," 3rd German edition, S. 67. 
5 Salomon, Deutsche vied. JFchnschr., Leipzig, 1877, Nos. 8 and 35 ; Centralbl. f. 
Physiol., Leipzig, Bd. vi. S. 512 ; Huppert, Centralbl. f. Physiol., Leipzig. Bd. vi 
S. 394. 
6 Salomon, loc. cit. 
7 Leube, Pirchow's Archiv, Bd. cxiii. S. 391. 
