THE CHEMISTRY OF THE BODY. J 



saccharides of smaller molecule than the starches, called dextrins, and 

 a disaccharide, maltose, and giving as the final product the mono- 

 saccharide, dextrose. 



The first-formed dextrin products of the hydrolysis of the starches 

 are called erythro-dextrins, because they give a red colour with iodine ; 

 the later-formed substances are called achroo-dextrins because they 

 give no colour with iodine, and consist of smaller molecules than the 

 erythro-dextrins. The process of hydrolysis of a polysaccharide may be 

 summarised in the equation 



Inosite. Inosite is a substance found in muscle and formerly 

 called muscle-sugar. It has the formula C 6 H 12 6 + 2H 2 0, but does not 

 belong to the carbohydrate group, being a benzene derivative. It 

 does not reduce an alkaline solution of cupric sulphate, does not rotate 

 polarised light, and is non-fermentable. 



(II.) The second group of non-nitrogenous substances, those in 

 which the oxygen of the molecule is insufficient to combine with the 

 hydrogen, consists of the Fats. The chief fats found in the body are 

 tristearin, C 3 H 5 (C 18 H 35 2 ) 3 , tripalmitin, C 3 H 5 (C 16 H 31 2 ) 3 , and triolein, 

 C 3 H 5 (C 18 H 33 2 ) 3 . They are compounds of the corresponding fatty 

 acids, stearic, palmitic, and oleic, with the trivalent alcohol, glycerol. 

 Stearic and palmitic acids are saturated compounds, and the former 

 and its esters, being higher in the series than palmitic acid and its 

 esters, have a higher melting point. Oleic acid is unsaturated, and 

 both the acid itself and triolein have a relatively low melting point, 

 being fluid at room temperature. 



Fats are insoluble in water, but are soluble in ether or in warm 

 alcohol. They are decomposed on heating with alkalies, the fatty 

 acid uniting with the alkaline base to form a soap and the glycerol 

 being set free (saponification). If a neutral fat, such as pure olive oil, 

 is shaken up with water, the fat becomes broken up into fine globules 

 which run together again when the shaking ceases. If, however, some 

 soap is present, each globule becomes coated with a layer of soap 

 molecules, which so reduce the surface tension between the fat and 

 the water that the globules remain apart. Siich a suspension of fat 

 globules is called an emulsion. A fine emulsion of this kind occurs in 

 the lymph during the absorption of fat, the place of the soap being 

 probably taken by the proteins of the lymph itself. 



Lipoids. The term lipoids includes a number of substances which 

 resemble fats in being soluble in ether. The commonest of these are 

 lecithin and cholesterol, which are constantly associated in the body, 



