CHEMICAL BASIS OF THE ANIMAL BODY. 885 



tion six times its weight of cold, but only two parts of boiling, water ; it is entirely 

 insoluble in alcohol and ether. It is fully precipitated from its solutions by the 

 addition of lead acetate and ammonia. 



When freshly dissolved, its aqueous solution possesses a specific dextro-rotatory power of +93.1 

 for sodium light"; this diminishes slowly on standing, rapidly on boiling, until it finally remains 

 constant at -(-52.5. The amount of rotation is independent of the concentration of the solution. 



Lactose unites readily with bases, forming unstable compounds; from its metallic compounds 

 the metal is precipitated in the reduced state on boiling; it reduces copper salts as readily as 

 dextrose, but to a less extent, viz., in the ratio of 70 : 100. 



Lactose is generally stated to admit of no direct. alcoholic fermentation; this 

 may, however, sometimes be induced by the prolonged action of yeast. By boiling 

 with dilute mineral acids lactose is converted into gal'actose, which readily undergoes 

 alcholic fermentation and possesses a greater rotatory power than lactose. 



It may be remarked here that though isolated lactose is incapable of direct alcoholic fermenta- 

 tion, milk itself may be fermented. Berthelot was unable in this direct alcoholic fermentation 

 to detect any intermediate change of the lactose into any other fermentable sugar. 



Lactose is, however, directly capable of undergoing the lactic and butyric fer- 

 mentation ; the circumstances and products are the same as in the case of dextrose 

 (see above). The action is generally productive of a collateral small quantity of 

 alcohol. . 



Lactose is thus distinguished from dextrose by its smaller solubility in water, 

 insolubility in alcohol, crystalline form, lower cupric oxide reducing power, and its 

 incapability of undergoing direct alcoholic fermentation. 



Preparation. After the removal of the casein and other proteids of the milk, 

 the mother-liquor is evaporated to the crystallizing point ; the crystals are purified 

 by repeated crystallization from warm water. 



4. Inosit. C 6 H 12 6 + 2H 2 0. 



This substance occurs but sparingly in the human body ; it was found originally 

 by Scherer * in the muscles of the heart. Cloetta showed its presence in the lungs, 

 kidneys, spleen, and liver, 2 and Miiller in the brain. 3 It occurs, also, in diabetic 

 urine and in that of u Bright' s disease," and is found in abundance in the vegetable 

 kingdom. 



Pure inosit forms large efflorescent crystals (rhombic tables) ; in microscopic 

 preparations it is usually obtained in tufted lumps of fine crystals. Easily soluble 

 in water, it is insoluble in alcohol and ether. It possesses no action on polarized 

 light, and does not reduce solutions of metallic salts. 



It admits of no direct alcoholic, but is capable of undergoing the lactic, fermen- 

 tation ; according to Hilger, 4 the acid formed is sarcolactic. It is unaltered by 

 heating with dilute mineral acids. 



Preparation. It may be precipitated from its solutions by the action of basic 

 lead acetate and ammonia; the lead is then removed by sulphuretted hydrogen, and 

 the inosit precipitated with excess of alcohol. 



As a special test (Scherer's) may be mentioned the production of a bright violet 

 color by careful evaporation to dryness on platinum foil, with a little ammonia and 

 calcium chloride. 



5. Dextrin. C 6 H 10 5 . 



By boiling starch-paste with dilute acids, or by the action of ferments, the starch 

 is converted into an isomeric body, to which, from its action on polarized light, the 

 name dextrin has been given. It is soluble in water, but is precipitated by alcohol. 

 It does not undergo alcoholic fermentation until after it has been changed into 

 dextrose, nor can it reduce metallic salts. It yields a reddish port-wine color with 

 iodine, which disappears on warming and does not return on cooling. Further 

 action of acids or of ferments converts dextrin into dextrose. Dextrin is present 

 in the contents of the alimentary canal after a meal containing starch, and has also 

 been found in the blood. 



There is not the least doubt that several modifications of dextrin exist, and may 

 be obtained by the action of acids and ferments on starch. Of these two of the 



i Ann. d. Chem. u. Pharm., Bd. Ixxiii., S. 322. 2 ibid., Bd. xcix., S. 289. 



s Ibid., Bd. ciii., S. 140. 4 ibid., Bd. clx., S. 333. 



