114 LACTOSE. 



reducing) power on treatment with acids affords a further convenient 

 means of discrimination between lactose and dextrose. 



Phenyl-lactosazone. C^H^N/^. 



This compound of lactose with phenyl-hydrazin is formed under 

 conditions similar to those already described for the preparation of the 

 analogous compound of dextrose. It is soluble in 80 90 parts of 

 boiling water and melts at about 200. It crystallises readily in the 

 form of yellow needles which, unlike the crystals of phenyl-maltosazone, 

 are usually aggregated into clusters. 



Lactose is readily capable of undergoing a direct lactic fermentation 

 and this occurs characteristically in souring milk. The exciting cause is 

 doubtless ordinarily an organised ferment, but there is also some 

 evidence of the existence in the alimentary canal of an enzyme which 

 can effect the same conversion. The circumstances and products of the 

 conversion are the same as for dextrose and saccharose. 



Although isolated lactose is unaffected by yeast, milk itself is capable of under- 

 going, under the influence of certain ferments, an alcoholic fermentation, and this 

 has been employed from very early times by the inhabitants of certain districts of 

 Eussia in the preparation of Kumys and Kephir from rnare's-milk. Of late years 

 these fluids have attracted much attention in virtue of their supposed therapeutic 

 action in certain wasting diseases. Very little is as yet known as to the real 

 nature of the changes which occur during the fermentation, but they are probably 

 extremely complex and due to the presence of several organised ferments 1 . Kephir 

 ferment is a commercial article in Russia, obtainable at the apothecaries. 



The non-assimilability of saccharose and maltose has already been 

 referred to, and experiment has shown that lactose is similarly incapable 

 of assimilation, for when injected into the blood-vessels it appears 

 unaltered in the urine 2 . It is therefore presumably changed in the 

 alimentary canal into some form of sugar which is assimilable, it may 

 be into dextrose and galactose. It does not appear that any such 

 conversion can be markedly observed, if at all, under the action of any 

 of the secretions of the alimentary canal, hence the change may more 

 probably take place, as in the case of maltose, rather during than before 

 the passage of the sugar through the intestinal walls. 



This non-assimilability of lactose is certainly remarkable when it is 

 remembered that it is in this form that young animals receive their 



1 There is an extensive literature on this subject, of which the following are of 

 most comprehensive interest. Biel, Unters. iiber den Kumys, Wien, 1874, and St 

 Petersburg, 1881. Abst. in Maly's Bericht. 1874, p. 166, 1886, p. 159. Struve, 

 Ber. d. d. chem. Gesell. Jahrg. 1884, Sn. 314, 1364. Krannhals, Deutsch. Arch. f. 

 klin. Med. Bd. xxxv. (1884), S. 18. Hammarsten (Swedish). See Abst. in Maly's 

 Bericht. 1886, p. 163. 



2 Dastre, Compt. Rend. T. xcvi. (1883), p. 932. Gompt. Rend. Soc. Biol. (9), T. 

 i. (1889), p. 145. De Jong (Dutch Diss.). See Maly's Bericht. 1886, p. 445. 



