34 



CARBOHYDRATES. 



(4. Gum, C, HooOi , occurs in vegetable juices (especially in acaciie and mimosa?), also in the 

 salivary glands, mucous tissue, lungs, and urine ; is partly soluble in water (arabin), partly 

 swells up like mucin (bassorin). Alcohol precipitates it. It is fermentable, and when boiled 

 with dilute acids yields a reducing sugar.) 



(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 

 algre ; is transformed into glucose by dilute sulphuric acid. ) 



(7. Paramylum occurs in the form of grauules resembling starch, in the infusorian, 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 ; rendered blue by sulphuric acid 



Fig. 239. 

 a, "West Indian arrow -root ; c, Tahiti arrow-root ; d, Potato starch. 



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 7 (NOo) 3 5 , which dissolves in a mixture of ether and alcohol and forms coUodion. ) 



(9. Tunicin is a substance resembling cellulose, and occurs in the integument of the Tunicata 

 or Ascidians. ) 



IV. Division. This contains the carbohydrates which do not ferment. 



1. Inosit (phaseo-mannit, muscle-sugar) occurs in muscle (ScJierer), lung, liver, spleen, 

 kidney, brain of ox, human kidney ; pathologically in urine and the fluid of echinococcus. In 

 the vegetable kingdom, in beans (leguminosse), and the juice of the grape. It is an isomer of 

 grape-sugar ; optically it is inactive, crystallises in warts with 2 molecules of water, in long 

 monoclinic crystals ; it has a sweet taste, is insoluble in water, does not give Trommer's re- 

 action, is capable of undergoing only the sarcolactic acid fermentation. (Nearly allied are 

 Sorbin, from sorbic acid ScyUit, from the intestines of the hag-fish and skate and Eukalyn, 

 arising from the fermentation of melitose. ) 



IV. Derivatives of Ammonia and their Compounds. 

 The ammonia derivatives are obtained from the proteids, and are decomposition -products of 

 their metabolism. 



(1) Amines, i.e., compound ammonias which can be obtained from ammonia (NH 3 ), or from 

 ammonium-hydroxide (NH 4 - OH), by replacing one or all the atoms of H by groups of carbo- 

 hydrates (alcohol radicals). The amine derived from one molecule of ammonia is called mona- 

 mine. "We are only acquainted with 



CH, 

 CH a 



as decomposition-products of cholin (neurin) and of kreatin. Neurin occurs in lecithin in a 

 very complex combination (see Lecithin, p. 381, and also 23). 



(2) Amides, i.e., derivatives of acids, which have exchanged the hydroxyl (HO) of the acids 

 for NH 2 . Urea, CO(NH 2 ) 2 , the biamid of C0 2 , is the chief end-product of the metabolism of 

 the nitrogenous constituents of our bodies (see Urine, 256). Carbon dioxide containing water 

 = CO(OH) 2 , where both OH are replaced by NH 2 thus we get CO(NH 2 ) 2 , urea. 



(3) Amido-acids, i.e., nitrogenous compounds, which show partly the character of an acid 

 and partly that of a weak base, in which the atoms of H of the acid-radical are replaced by 

 XH 2 , or by the substituted ammonia groups. 



(a) Glycin (or amido-acetic acid, glycocoll, gelatin- sugar, 177, 2) is formed by boiling 

 gelatin with dilute sulphuric acid. It has a sweet taste (gelatin-sugar), behaves as a weak acid, 

 but also unites with acids as an amine-base. It occurs as glycin + benzoic acid = hippuric acid 

 in urine ( 260) ; and also as glycin + cholalic acid - glycocholic acid in bile ( 177). (b) Leucin 



H r 



CH 3 J 



N Methylamine and Tri-Methylamine 





N, 



