112 MALTOSE. 



fluid 1 the amount of cuprous oxide which separates out is only 

 about two-thirds of that which would be reduced by an equal 

 weight of dextrose, or in other words 66 parts of dextrose reduce 

 as much as 100 parts of maltose. Bearing in mind that maltose 

 may be readily converted into dextrose by boiling with dilute 

 acids with a corresponding change of its optical and reducing 

 powers, while dextrose is of course unaltered by this operation, it 

 is easy to base upon the above facts a method of identifying the 

 two sugars. As a further difference between the two it may 

 be stated that Barfoed's reagent 2 is not reduced by maltose, 

 whereas it is by dextrose. 3 In this respect maltose resembles 

 lactose (milk-sugar) which also does not reduce this reagent. 



Phenyl maltosazone. C 2 JJ. S2 N 4 O 9 . 



This compound of maltose is obtained by the action of phenyl- 

 hydrazin upon it in presence of acetic acid in the way already 

 described (p. 104) for the preparation of the analogous compound 

 with dextrose. It crystallises readily in minute yellow needles 

 and is characterised by being (unlike phenyl-glucosazone) soluble 

 in about 75 parts of boiling water, and still more soluble in hot 

 alcohol. Its melting point 206 is practically the same as that of 

 phenyl-glucosazone. 



The researches of Brown and Heron (see above, p. 59) showed 

 that whereas pancreatic juice rapidly converts starch-paste into 

 maltose and a little dextrose, an extract of the mucous membrane 

 of the small intestine or the tissue itself, while acting but feebly 

 on starch-paste rapidly converts maltose into dextrose. They 

 hence surmised that maltose would be found to be a non-assimil- 

 able sugar, requiring like cane-sugar to be converted into the 

 vsimpler dextrose before absorption. More recent experiments have 

 confirmed this view, 4 for it has been found that if maltose be in- 

 jected into the blood-vessels it is largely excreted in an unaltered 

 form in the urine. 5 The converting action of extracts of the in- 

 testinal mucous membrane is strikingly less than that of the 

 tissue itself ; from this it may perhaps be inferred that the change 

 into dextrose takes place rather during than previous to absorp- 

 tion. This fact corresponds closely to the well-known views as to 

 the changes which peptones similarly undergo during their passage 



1 Solution of hydrated cupric oxide in caustic soda, in presence of the double 

 tartrate of sodium and potassium (Rochelle salt). See Soxhlet, loc. cit. 



2 Dissolve I part of cupric acetate in 15 parts of water : to 200 c. c. of this solution 

 add 5 c.c. of acetic acid containing 38 p.c. of glacial acid. Jn.f.pr. Chem. (2), Bd. vi. 

 (1872). S. 334. 



8 Musculus n. von Mering, loc. cit. 



4 But cf. previously Bimmerinann, Pfliiger's Arch. Bd. xx. (1879), S. 201. 



5 Philips, Diss. Amsterdam, 1881. See Abst. in Maly's Bericht. 1881, p. 60. See 

 also Bourquelot, Compt. Rend. T. XCYII. (1883), pp. 1000, 1322; T. xcvin. p. 1604. 

 Journ. de t'Anat. et de la Physiol. T. xxn. (1886), p. 161. 



