12 CHEMICAL CONSTITUENTS OE BODY AND EOOD. 
intermediate product in the formation of dextrose by mineral acids from 
starch. An amylolytic ferment in blood serum, capable of forming 
dextrose from starch, acts similarly. 1 A small quantity occurs in 
normal urine. 2 It is readily soluble in water, is very sweet, and 
ferments slowly with yeast. Its general characters are like those of 
maltose, but its osazone forms fine yellow needles which melt at 150° C. 
Lactose or milk-sugar occurs only in milk, and occasionally in the 
first days of lactation in the urine in small quantities. 3 
It crystallises in rhombic prisms, which contain one molecule of water 
of crystallisation (Fig. 3). It is soluble in six 
parts of cold, and two and a half parts of hot 
water; it is therefore less soluble than the 
other sugars. It has only a faint sweet 
taste. Aqueous solutions are dextro-rotatory 
0) D = + 59°-3 (Hesse) 4 and +52°-5 for the 
/) V t^(/ hydrate at 20° C. (Schmoger). 5 Its reducing 
power as tested by Fehling's solution is 
intermediate between that of dextrose and 
maltose. 6 Lactose is very resistant to the 
Fig. 3.— Lactose crystals.— After inverting ferment of yeast, and so undergoes 
Iey " the alcoholic fermentation very slowly. It 
is, however, rapidly inverted by the Kephir fungus, and of all the 
sugars is that most readily affected by the B. lactis; the lactic acid 
fermentation occurs in two stages, as follow : — 
1. C 12 H 22 O u + H 2 = 4C 3 H 6 3 
(lactose) (lactic acid) 
2. 2C ? H 6 03 = C 4 H 8 2 + 2C0 2 + 2H 2 
lactic acid) (butyric acid) 
With phenylhydrazine, lactose yields phenyl-lactosazone, which readily 
crystallises in needles (Fig 4). It is soluble in eighty to ninety parts 
of boiling water. Its melting point is 200° C. 
Among the rarer disaccharid.es must be mentioned trehalose (from certain 
fungi), and melebiose, a saccharose which with tZ-fructose (levulose) is obtained 
from raffinose. Raffi/nose 1 is an interesting sugar found in Eucalyptus manna, 
cotton seeds, and barley. It is a trisaccharide, consisting of a combination 
of dextrose, levulose, and galactose. 
The polysaccharides. — To this group belong a large number of 
carbohydrates of high molecular weight, and with the formula (C 6 H 10 O 6 ) n . 
Their molecular weights differ a good deal, but have not yet been 
determined directly by chemical methods. 8 They are not crystalline, 
are indiffusible, and, as a rule, insoluble in cold water. In hot water 
they partially dissolve, forming opalescent solutions. Like the proteids, 
1 Rohmann, Ccntralbl.f. d. med. Wissensch., Berlin, 1893, S. 849. 
2 Lemaire, Ztschr.f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 442. 
3 The most recent observations on lactose in the urine of women after childbirth are by 
Lemaire, Ztschr.f physiol. Choi.. Strassburg, 1896, Bd. xxi. S. 442. Pavy, Lancet, London, 
1897, vol. i.]>. 1075. See also Hofmeister, Ztschr.f. physiol. Chem., Strassburg, Bd. i. S. 101. 
4 Ann. d. ('Jinn., Leipzig, 187.1. Bd. clxxvi. S. 98.' 
5 Bcr. d. deutsch. chem. Gesellsch., Berlin, 1SS0, Bd. xiii. S. 192:.'. 
I Ten c.r. of Fehling's solution = 0-06334 lactose ; see footnote 1, p. 11. 
7 Loiseau, Compt. rend. Arm/. ,1. sc ., Paris, 1876, tome lxxxii. p. 105S ; Ber. d. deiUsch. 
chem. Gesellsch.., Berlin, Bd. ix. S. 732 ; Seheibler, ibid., 1886. Bd. xix. S. 2868. 
8 By Raoult's method of determining the lowering of the freezing point in very dilute 
solutions, Brown and Morris {Journ. Chem. Soc. London, 188S. p. 610), have provisionally 
