test), which also reduces the cupric salt to a cuprous. (N.B. As other substances besides sugar have a reducing action on copper, it is advisable to confirm with tests 3 and 4).

PRACTICAL APPLICATIONS. *(a) To ascertain the presence of sugar in blood.-Agitate blood with four times its bulk of alcohol, allow the mixture to stand, and then filter; extract the residue with a little hot water and rub it thoroughly in a mortar with animal charcoal, add a little more hot water, and filter. Add the aqueous to the alcoholic filtrate, and evaporate to near dryness over a water bath. Apply tests 3, 4, and 5.

*(b) To ascertain the presence of sugar in liver tissue.Wash out the liver of a recently killed animal by passing a stream of water, injected by means of a syringe, through the portal vein. The fluid issuing from the hepatic veins will be found by tests 3 and 5 to contain sugar, the quantity diminishing as the washing out is proceeded with, till no reaction with tests is attained. If after the sugar has been washed out, the liver be laid aside for an hour or so, and the washing again performed, a small quantity of sugar will be detected, showing that sugar has been formed by the liver-cells since the removal of the first portion.

(c) To determine the quantity of sugar present in urine. (vide Urine.)

(4) LACTOSE. CH12O6 (syn. Milk sugar), is a characteristic constituent of milk. It is found in no other secretion. The large quantity always present in milk is an evidence of the important part which sugar takes in the nutrition of the young mammal.

Chemical properties.-Like glucose it reduces copper salts from their alkaline solutions. It differs from glucose in not readily undergoing vinous fermentation when yeast is added. Boiled for some hours with dilute acids it forms galactose, a sugar isomeric with glucose, and like it, ferments readily on the addition of yeast. (For estimation of lactose, see Milk.)

(5) INOSITE. C6H12O6 (syn. Muscle sugar) was originally discovered by Scherer in the muscular substance of the heart. It is a constant constituent of voluntary muscular fibre, and is also found in the tissues of the kidney, liver, spleen, brain, and testicle. In certain diseases, as Diabetes, Bright's disease, Phthisis, Syphilitic cachexia, and Typhus, it is met with in the urine.

*To obtain inosite from urine.-The urine to be tested for inosite is completely precipitated with sugar of lead, filtered, and the warm filtrate treated with basic acetate of lead as long as any precipitate is formed. It is better that the urine should be concentrated to one-fourth before it is precipitated. The lead-precipitate collected after twelve hours' standing is washed, suspended in water, and then decomposed by sulphuretted hydrogen. After the filtrate has been left at rest a short time, a small quantity of uric acid separates from it; this is removed by filtration, and the fluid so concentrated as to remain permanently turbid when treated with an equal volume of alcohol. It is then heated until the turbidity disappears, and allowed to stand one or two days. The crystalline mass thus obtained is purified by re-crystallisation, and then subjected to the tests of nitric acid, ammonia, and chloride of calcium, as well as of tartrate of copper (Neubauer and Vogel).

Chemical properties.-Although inosite is isomeric with glucose, it presents none of the characteristic reactions of the group; thus it does not reduce the copper salts 1 from their alkaline solutions, nor does it undergo vinous fermentation with yeast, nor has it any action on polarized light.

1 Although no reduction of copper takes place a green solution results, from which, after a time, a flocculent, greenish precipitate is separated, the upper part of the fluid becoming blue. If the precipitate is separated by filtration, and the filtrate again boiled, the same play of colour will be again observed. This reaction is often observed in urine.

I

The following is a characteristic and delicate test for inosite : a small quantity of the fluid containing inosite is evaporated to dryness on a piece of platinum foil with a drop or two of nitric acid, the residue moistened with ammonia and calcium chloride, which on evaporation yields a beautiful rose tint.

Requirements for Demonstration I.

MATERIALS-Powdered starch. Yeast. Grape sugar (Honey). Oysters.

REAGENTS.-Solutions of iodine: cupric sulphate : sodium potassio-tartrate. Liquor potassæ. Dilute sulphuric acid. Red and blue litmus-paper.

APPARATUS.—Test-tubes. Water bath.

Spirit-lamp

or Bunsen-burner. Hydrometer. Urine-glass. Ther

mometer.

I. The saponifiable or neutral fats are formed by the union of a fatty acid radical with glycerin; thus, stearin consists of three parts of the acid radical, stearyl C18H35O, which has replaced three atoms of the typical hydrogen from CHO, glycerin, to

form the new substance

C3H5

C2H

C3H5 Og, or stearin; 3(C18H350) 39

and in a similar manner the radicals of palmitic and oleic acid unite with glycerin to form palmitin,

CH

3 (C16H310)

Os, and olein,

(6) PALMITIN, C51H98O6. This substance is obtained from human fat by separating it from the

stearin with which it is combined, by melting in a

water bath, temp. 62°.8 C., and extracting with ether at this temperature. The etherial solution on evaporation deposits palmitin.

(7) STEARIN, C57H110O6. Is obtained from human fat after the removal of the palmitin by raising the temperature of the water bath to 69°7 C. adding an equal quantity of ether. The etherial solution being decanted on cooling deposits stearin.

(8) MARGARIN consists or 10 per cent. of stearin and 90 per cent. of palmitin. Margarin is obtained. by heating fat in a water bath, and stirring with an equal quantity of alcohol for some time; the alcoholic solution is then filtered off, and on cooling it will deposit delicate needle-shaped crystals, which arrange themselves in whorled groups or feathers. The melting-point of margarin is 47°8 C., which is considerably lower than the melting-point of its constituent components.

(9) OLEIN, C57H10406 Olein can be obtained tolerably pure by heating fat in a flask, and filtering it when cold; the filtered solution is concentrated by evaporation, and by the addition of water the olein is separated; the product is then exposed to cold at 。° C., and the solid portion submitted to pressure; the liquid that separates is almost pure olein.

Human fat is formed of a mixture of stearin, palmitin, and olein; the two former constitute about threefourths of the fat of the body and form the solid portion; whilst the olein represents the remaining fourth, and is the liquid or oily constituent.