51: 



CARBOHYDRATES, 



B 



(4. Melitose, from Eucalyptus-manna; MelezitOSC, from Larch-manna; 

 Trehalose (Mycose), from Ergot ; all right-rotatory, and do not reduce alkaline 

 cupric solutions.) 



III. Division, contains carbohydrates with the formula, C 6 H 10 5 , which may 

 be regarded as anhydrides of the second division. 



1. GrlyCOgen, with a rotatory power of 211 (Bohm and Hoffmann, Kiilz), does 

 not reduce cupric oxide. It occurs in the liver (p. 350), muscles, many embryonic 

 tissues, the embryonic area of the chick (Kiilz), in normal and pathological 

 epithelium (Schiele), and according to Pavy, in the spleen, pancreas, kidney, ovum, 

 brain and blood, together with a small amount of glucose. It also occurs in the 

 oyster and some of the molluscs (Bizio). 



2. Dextrin was discovered by Limpricht in the muscles of the horse. It is 

 right-rotatory = + 138, soluble in water and forms a very sticky solution, from 

 which it is precipitated by alcohol or acetic acid ; it is tinged slightly red with 

 iodine. It is formed in roasted starch, (hence it occurs in large quantity in the 

 crust of bread see Bread, p. 472), by dilute acids, and in the body by the action 

 of ferments (p. 294). It is formed from cellulose by the action of dilute sulphuric 

 acid. It occurs in beer, and is found in the juices of most plants. 



(3. Amylum or Starch 



occurs in the " mealy" parts of 

 many plants, is formed within 

 vegetable cells, and consists of 

 concentric layers with an ex- 

 centric nucleus (Fig. 176, B). 

 The diameter of starch grains 

 varies greatly with the plant 

 from which they are derived. 

 At 72C. it swells up in water 

 and forms mucilage ; in the 

 cold, iodine colours it blue. 

 Starch grains always contain 

 more or less cellulose and a sub- 

 stance which is coloured red 

 with iodine (erytlirogranulose) 

 (see p. 294). It and glycogen 

 are transformed into dextrose by 

 certain digestive ferments in the 

 saliva, pancreatic and intestinal 

 juices, and artificially by boiling 

 with dilute sulphuric acid.) 

 (4. Gum occurs in vegetable juices (specially in acacise and mimosae), is partly 

 soluble in water (arabin), partly swells up like mucin (bassorin). Alcohol pre- 

 cipitates it.) 



(5. Inulin, a crystalline powder occurring in the root of chicory, dandelion, and 

 specially in the bulbs of the dahlia; it is not coloured blue by iodine.) 



(6. Lichenin occurs in the intercellular substance of Iceland moss (Cetraria 

 islandica) and algse; is transformed into glucose by dilute sulphuric acid.) 



(7. Paramylum occurs in the form of granules resembling starch, in the infus- 

 orian, Euglena viridis.) 



(8. Cellulose occurs in the cell-walls of all plants (in the exo-skeleton of 

 arthropoda, and the skin of snakes) ; soluble only in ammonio-cupric oxide ; ren- 

 dered blue by sulphuric acid and iodine. Boiled with dilute sulphuric acid, it 

 yields dextrin and glucose. Concentrated nitric acid mixed with sulphuric acid 

 changes it (cotton) into nitro-cellulose (gun cotton) C 6 H r (N0 2 )30 5 , which dissolves 

 in a mixture of ether and alcohol and forms collodion.) 



Fig. 176. 



Section of a wheat grain d, starch-corpuscles 

 within vegetable cells; B, starch-corpuscles 

 with concentric markings (See also Fig. 

 173). 



