466 THE CARBOHYDRATES. 



and levulose. Oxidized with nitric acid it is decomposed into glucic acid and 

 oxalic acid. 



III. Polysaccharids or amyloses, result, as anhydrids of members of the first 

 division, from the union of many molecules of the monosaccharids. Many of 

 them do not undergo fermentation. They yield colloid solutions, do not diffuse 

 and do not crystallize. 



1. Glycogen, with a rotatory power of +211, devoid of reducing action, 

 occurs in the liver, the muscles, many embryonal tissues, the fetal membranes, 

 the rudimentary embryo of the chick and in part in normal and pathological 

 epithelium. It is present in small amounts in many organs: testicle, lung, skin, 

 and in pus and inflammatory foci. It has been found in considerable amount in 

 the body of the diabetic, in the brain, the pancreas, and cartilage. It occurs also 

 in oysters and other molluscs, but it may be present in the cells of all of the tissues 

 and of all classes of animals. Errera found glycogen in yeast. 



2. Dextrin is dextrorotatory +138, forms a viscid solution with water, 

 from which it is precipitable by alcohol and acetic acid, and is discolored feebly 

 red by iodin. It results from scorched starch (and is therefore abundant in bread- 

 crusts) through the action of dilute acids, and in the body through the action 

 of ferments. It is formed from cellulose by treatment with dilute sulphuric acid. 

 It occurs also in beer. In the vegetable kingdom it is present in most vegetable 

 juices. 



3. Starch is present in the mealy portion of many vegetables, partly con- 

 sisting of organized granules in layers forming within the vegetable cells, with a 

 generally excentric nucleus, and partly, though less commonly, occurring unformed 

 in vegetables. The diameter of the starch-granule varies considerably in different 

 plants. It is, for instance, from 0.14 to 0.18 mm. in the potato and only 0.004 

 mm. in the seed of the red beet. In water at a temperature of 72 C. it swells 

 as a paste. It is stained blue by iodin only in the cold. The starch-granules 

 contain further always more or less cellulose, as well as a body stained red by 

 iodin (erythrogranulose) . The transformation of starch and glycogen takes place 

 through the action of the saliva, the pancreatic and the intestinal juice; both 

 are transformed into dextrose by dilute sulphuric acid. 



4. Gum, C 10 H 20 O 10 , occurs in man in organs containing mucus, such as the 

 salivary glands, the mucoid tissues, the lungs, and in bile, occasionally in albuminous 

 fluids, and in small amounts in the urine. It is susceptible of fermentation and is 

 decomposed by boiling with dilute acids into a body reducing copper oxid. In 

 the vegetable kingdom gum is found in the juices particularly of acacias and 

 mimosas, partly soluble in water (arabin), partly swelling up like mucus (bassorin). 

 It is precipitated by alcohol. Wood-gum (pentosan, C 5 H S O 4 ) occurs abundantly 

 in fibrous vegetable matters consumed by herbivora as food. On heating with 

 dilute acids there result by hydration pentoses, in the same way as dextrose is 

 formed from starch. There are two pentosans: xylan, which yields xylose, and 

 araban, from which arabinose results. Pentosan results from the oxidation of 

 cellulose and starch, i atom of C being transformed into CO 2 . 



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

 and in the bulbs of dahlia variabilis, is not stained blue by iodin. 



6. Lichenin, lichen-starch, the intercellular substance of lichens, especially 

 of Iceland moss (cetraria Icelandica), and of algae. It can be transformed into 

 glucose by dilute sulphuric acid. 



7. Cellulose, C 6 H 10 O 5 , the cellular tissue of all vegetables, is found also in the 

 integument of tunicates, the exoskeleton of arthropods and the skin of snakes. 

 It is soluble only in ammoniated cupric oxid and is colored blue by sulphuric 

 acid and iodin. On boiling with dilute sulphuric acid dextrin and glucose are 

 formed. It is transformed (cotton) by concentrated nitric acid mixed with 

 sulphuric acid into nitro-cellulose (gun-cotton, C 6 H 7 (NO 2 ) 3 p 5) ), which, dissolved 

 in a mixture of ether and alcohol, forms collodion. Tunicin, a body similar to 

 cellulose, occurs in the integument of tunicates (molluscs). Cellulose is dissolved 

 in the intestine of herbivora with the aid of bacteria. 



For the sake of completeness, inosite, C 6 H 12 O 6 , hexahydrohexaoxybenzol, 

 muscle-sugar, phaseomannite, bean-sugar, may be discussed at this point. This is 

 not a true sugar, but it has a sweet taste. It occurs in the muscles, the lungs, 

 the liver, the spleen, the kidneys, the brain of the ox, and the kidneys of man; 

 pathologically in the urine and in echinococcus-fluid. It is widely distributed in 

 the vegetable kingdom, especially in beans (Leguminosae) and in grape-juice. It is 

 optically inactive, generally crystallizes like cauliflower, with two molecules of 

 water, in long monoclinic crystals, insoluble in alcohol or ether; it does not re- 



