14 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 

 and so on, until at last we get to 



(C 6 H 10 5 ) 4 + H 2 = (C 6 H 10 5 ) 2 + C 12 H 22 U 



(dextrin) (dextrin) (maltose) 



and finally 



(C,.,H 10 5 ). 2 + H 2 = C 12 H, 2 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., 



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 sphere-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 

 algae. 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. f. d. ges. PhysioL, Bonn, 1897, Bd. Ixvi. 

 S. 545). 



3 Brown, Morris, and Millar, loc. cit. 



3 Kulz, "Beitr. z. Path, des Diabetes," Marburg, 1894, S. 130. ; Worm-Miiller, Arch. 

 f. d. ges. PhysioL, Bonn, 1884, Bd. xxxiv. S. 576 ; 1885, Bd. xxxvi. S. 172 ; F. Hofmeister, 

 'Arch. f. exper. Path. u. PharmaJcoL, 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 Ldkaref. Forh., vol. xxviii., quoted by Hammarsten, in "Physiol. 

 Chem.," 3rd German edition, S. 67. 



5 Salomon, Deutsche med. Wchnschr., Leipzig, 1877, Nos. 8 and 35 ; CentralU. f. 

 PhysioL, Leipzig, Bd. vi. S. 512 ; Huppert, Centralbl. f. PhysioL, Leipzig. Bd. vi 

 S. 394. 



6 Salomon, loc. cit. 



7 Leube, Virchow's Archiv, Bd. cxiii. S. 391. 



